Advances in Celebration

2021 Issue 2 // Volume 117 THE BRIDGE The Magazine of IEEE-Eta Kappa Nu

Modeling of organic semiconductor conduction parameters with reference to inorganic semiconductors

Modeling of organic semiconductor metallic contact and optoelectronic parameters with reference to inorganic semiconductors

A review of Schottky junction solar cells

2020 Outstanding Chapter Award Winners SOLAR CELL Celebrating 50 Years with IEEE-HKN IEEE-HKN AWARDS PROGRAM THE BRIDGE As the Honor Society of IEEE, IEEE-Eta Kappa Nu provides opportunities The Magazine of IEEE-Eta Kappa Nu to promote and encourage outstanding students, educators and members. Visit our new website to view the awards programs, awards committees, 2021 ISSUE 2 | ADVANCES IN SOLAR CELL DESIGN list of past winners, nomination criteria and deadlines. 4 5 Editors-in-Chief Guest Editor ALTON B. ZERBY AND CARL T. KOERNER OUTSTANDING CHAPTER AWARD (OCA) Dr. Sahra Sedigh Sarvestani Dr. Amirhossein Ghods OUTSTANDING STUDENT AWARD (OSA) Recognizes chapters for excellence in activities and and Dr. Steve E. Watkins Presented annually to a senior who has proven service at the department, university and community outstanding scholastic excellence and high moral levels. The award is based on the content contained character, and has demonstrated exemplary service in their Annual Chapter Report for the preceding Features to classmates, university, community, and country. academic year. 14 20 27 (Deadline: 30 June) (Deadline: 31 July) Modeling of organic Modeling of organic A review of C. HOLMES MACDONALD OUTSTANDING OUTSTANDING YOUNG semiconductor conduction semiconductor metallic contact Schottky junction TEACHING AWARD (OTA) PROFESSIONAL AWARD (OYP) parameters with reference to and optoelectronic parameters solar cells Presented annually to electrical engineering Presented annually to an exceptional young engineer inorganic semiconductors with reference to inorganic professors who have demonstrated, early in their who has demonstrated significant contributions early semiconductors careers, special dedication and creativity in their in their professional career. teaching, as well as a balance between pressure for (Deadline: Monday after 30 April) Departments research and publications. 6 11 34 (Deadline: Monday after 30 April) IEEE-HKN ASAD M. MADNI OUTSTANDING TECHNICAL ACHIEVEMENT AND EXCELLENCE AWARD CHAPTER NEWS IEEE-HKN ANNIVERSARY PARTNER SPOTLIGHT DISTINGUISHED SERVICE AWARD Presented annually to a practitioner in the IEEE IEEE-HKN Debuts Successful Congratulations, John McDonald, Texas Instruments and IEEE-HKN Recognizes members who have devoted years technical fields of interest who has distinguished Practices Database IEEE-HKN for 50 Years Workshops Engage with Remote of service and lifetime contributions to Eta Kappa Nu himself or herself through an invention, development Engineering Students Consolidating Student Groups 12 (or IEEE-HKN), resulting in significant benefits to all or innovation that has had worldwide impact. AWARD SPOTLIGHT 36 of the Society’s members. (Deadline: Monday after 30 April) to Strengthen Research and Innovation Opportunities Congratulations, 2019-2020 STUDENT PROFILE (Deadline: Monday after 30 April) Outstanding Chapter Award Winners Hannah Schroeder 8 CHAPTER NEWS 13 39 IEEE-Eta Kappa Nu Board of Governors Toy Adapt-a-thon Uses Basic Circuit ECEDHA CORNER HISTORY SPOTLIGHT ECEDHA and IEEE-HKN Partner THE BRIDGE Magazine of President Governors Treasurer Knowledge to Create Holiday Joy for Student Success IEEE-Eta Kappa Nu Part II Jason Hui Preeti Bajaj Sandro Sartoni Ronald Jensen Karen Panetta Mu Beta Chapter’s Kidzineers STEM Governor, Regions 1-2 Governor At-Large Student Governor 2021 Outstanding Student Award 42 President-Elect Secretary Outreach Program Applications Due 30 June IN MEMORIAM James Conrad Michael Benson Ryan Bales Joseph Greene Bernard Sander Governor, Regions 3-4 Governor At-Large Student Governor 10 Innovator in Electronic Displays Past President Director 33 DONOR PROFILE Lawrence E. Tannas Jr. Christopher Hulya Kirkici SOCIETY SPOTLIGHT Edward Rezek Nancy Ostin Harnessing Strength in Numbers Sanderson Governor At-Large IEEE Solid-State Circuits Society: Former HKN Program Governor, Regions 5-6 Sean Haynes Lyle Feisel, Ph.D. Shaping the IC and the National President Manager Lorena Garcia MGA Electronics World John E. Farley Governor At-Large Stacey L. Bersani Governor, Regions 7-10

Editors-in-Chief: Managing Editor: IEEE-HKN INTERNATIONAL IEEE-Eta Kappa Nu (IEEE-HKN) was founded by Maurice L. Carr at the University of Illinois at Urbana- Champaign on 28 October 1904, to encourage Nancy Ostin excellence in education for the benefit of the public. IEEE-HKN fosters excellence by recognizing those students and professionals who have conferred honor Sahra Sedigh Sarvestani Assistant Managing Editor: HEADQUARTERS and Steve E. Watkins upon engineering education through distinguished scholarship, activities, leadership, and exemplary character as students in electrical or computer engineering, Stacey L. Bersani Editorial inquiries: IEEE-Eta Kappa Nu, or by their professional attainments. THE BRIDGE is the official publication of IEEE-HKN. Ideas and opinions expressed inTHE BRIDGE are those of the Editorial Board Members: 445 Hoes Lane, Piscataway, NJ 08854, USA Advertising Sales: Christine Cherevko individuals and do not necessarily represent the views of IEEE-HKN, the Board of Governors, or the magazine staff. Emily Hernandez, Marcus Huggans, US Toll Free: +1 800 406 2590 Copyright © 2020 IEEE. All rights reserved. Internal or personal use of this material is permitted with credit to the original source. Parties interested in reprinting Hulya Kirkici, Zahra Manzoor, [email protected] Outside US: +1 732 465 5846 or republishing IEEE material for advertising or promotional purposes or for creating new collective works for resale or redistribution must obtain permission. and Emmanuel Oyekanlu Design Company: Tumbleweeds, LLC Email: [email protected] | www.hkn.ieee.org Get in touch with Eta Kappa Nu Twitter: ieee_etakappanu Facebook: IEEE-HKN Subscription address and email changes: IEEE Contact Center US Toll Free: +1 800 678 4333 | Outside US: +1 732 981 0060 | Fax: +1 732 562 6380 | Email: [email protected]

THE BRIDGE HKN.ORG 3 IEEE-HKN AWARDS PROGRAM THE BRIDGE As the Honor Society of IEEE, IEEE-Eta Kappa Nu provides opportunities The Magazine of IEEE-Eta Kappa Nu to promote and encourage outstanding students, educators and members. Visit our new website to view the awards programs, awards committees, 2021 ISSUE 2 | ADVANCES IN SOLAR CELL DESIGN list of past winners, nomination criteria and deadlines. 4 5 Editors-in-Chief Guest Editor ALTON B. ZERBY AND CARL T. KOERNER OUTSTANDING CHAPTER AWARD (OCA) Dr. Sahra Sedigh Sarvestani Dr. Amirhossein Ghods OUTSTANDING STUDENT AWARD (OSA) Recognizes chapters for excellence in activities and and Dr. Steve E. Watkins Presented annually to a senior who has proven service at the department, university and community outstanding scholastic excellence and high moral levels. The award is based on the content contained character, and has demonstrated exemplary service in their Annual Chapter Report for the preceding Features to classmates, university, community, and country. academic year. 14 20 27 (Deadline: 30 June) (Deadline: 31 July) Modeling of organic Modeling of organic A review of C. HOLMES MACDONALD OUTSTANDING OUTSTANDING YOUNG semiconductor conduction semiconductor metallic contact Schottky junction TEACHING AWARD (OTA) PROFESSIONAL AWARD (OYP) parameters with reference to and optoelectronic parameters solar cells Presented annually to electrical engineering Presented annually to an exceptional young engineer inorganic semiconductors with reference to inorganic professors who have demonstrated, early in their who has demonstrated significant contributions early semiconductors careers, special dedication and creativity in their in their professional career. teaching, as well as a balance between pressure for (Deadline: Monday after 30 April) Departments research and publications. 6 11 34 (Deadline: Monday after 30 April) IEEE-HKN ASAD M. MADNI OUTSTANDING TECHNICAL ACHIEVEMENT AND EXCELLENCE AWARD CHAPTER NEWS IEEE-HKN ANNIVERSARY PARTNER SPOTLIGHT DISTINGUISHED SERVICE AWARD Presented annually to a practitioner in the IEEE IEEE-HKN Debuts Successful Congratulations, John McDonald, Texas Instruments and IEEE-HKN Recognizes members who have devoted years technical fields of interest who has distinguished Practices Database IEEE-HKN for 50 Years Workshops Engage with Remote of service and lifetime contributions to Eta Kappa Nu himself or herself through an invention, development Engineering Students Consolidating Student Groups 12 (or IEEE-HKN), resulting in significant benefits to all or innovation that has had worldwide impact. AWARD SPOTLIGHT 36 of the Society’s members. (Deadline: Monday after 30 April) to Strengthen Research and Innovation Opportunities Congratulations, 2019-2020 STUDENT PROFILE (Deadline: Monday after 30 April) Outstanding Chapter Award Winners Hannah Schroeder 8 CHAPTER NEWS 13 39 IEEE-Eta Kappa Nu Board of Governors Toy Adapt-a-thon Uses Basic Circuit ECEDHA CORNER HISTORY SPOTLIGHT ECEDHA and IEEE-HKN Partner THE BRIDGE Magazine of President Governors Treasurer Knowledge to Create Holiday Joy for Student Success IEEE-Eta Kappa Nu Part II Jason Hui Preeti Bajaj Sandro Sartoni Ronald Jensen Karen Panetta Mu Beta Chapter’s Kidzineers STEM Governor, Regions 1-2 Governor At-Large Student Governor 2021 Outstanding Student Award 42 President-Elect Secretary Outreach Program Applications Due 30 June IN MEMORIAM James Conrad Michael Benson Ryan Bales Joseph Greene Bernard Sander Governor, Regions 3-4 Governor At-Large Student Governor 10 Innovator in Electronic Displays Past President Director 33 DONOR PROFILE Lawrence E. Tannas Jr. Christopher Hulya Kirkici SOCIETY SPOTLIGHT Edward Rezek Nancy Ostin Harnessing Strength in Numbers Sanderson Governor At-Large IEEE Solid-State Circuits Society: Former HKN Program Governor, Regions 5-6 Sean Haynes Lyle Feisel, Ph.D. Shaping the IC and the National President Manager Lorena Garcia MGA Electronics World John E. Farley Governor At-Large Stacey L. Bersani Governor, Regions 7-10

THE BRIDGE HKN.ORG 3 Editors-in-Chief Guest Editors

THE BRIDGE, May 2021 Letter from Letter from the Editors-in-Chief the Guest Editor

By Dr. Amirhossein Ghods Dear IEEE-Eta Kappa Nu Members and Friends, Photovoltaic devices are an attractive and durable source of energy, This issue of THE BRIDGE magazine highlights current research in solar especially in areas with long hours of continuous sunshine and relatively cell design. We appreciate the efforts of our guest editor Dr. Amirhossein stable meteorological conditions. Major programs have been launched Ghods and the other authors. It is impossible to overstate the importance across the world to utilize and optimize the use of this natural resource, Dr. Sahra Sedigh of developing photovoltaic technology to address renewable and off-grid Dr. Amirhossein from the U.S. Department of Energy’s SunShot initiative to the Lighting energy needs. These global research efforts reflect an appreciation for Africa program founded by the singer/rapper Akon. Research by the Sarvestani improving technologies with respect to both performance and fabrication. Ghods World Bank and the International Finance Corporation indicates that Beta Chapter Innovations that provide higher operational efficiencies and lower Park Systems, Inc manufacturing costs are essential for growth in the use of photovoltaic more than 32 million people in Africa are currently meeting their basic energy technology. electricity needs through off-grid solar products. This level of solar energy usage is the CO2-equivalent to taking 383,745 cars off the road for The semiconductor solar cell was developed as a result of research a year. at Bell Telephone Laboratories. In 1940, Russell S. Ohl discovered the semiconductor p-n junction and observed that light produced a In recent years, the general perspective toward photovoltaic devices has small electrical current. Further work by the Bell Labs team of Daryl substantially changed from inefficient, bulky, and expensive to more Chapin, Calvin Fuller, and Gerald Pearson led to the “Bell Solar Battery” efficient, smaller, and more cost-effective devices. Solar cells made from with an efficiency of about six percent. The demonstration of this first semiconductors other than silicon have shown promising results, such as practical silicon solar cell was in 1954. Technical development and notably higher practical power conversion efficiency and easier fabrication commercialization have proceeded since. processes. Moving beyond single-junction devices has also opened the We welcome your feedback and remind you that THE BRIDGE is available door to highly efficient devices that capture a much larger portion of the on the IEEE app as well as the magazine website. Each issue has a variety solar spectrum than conventional silicon-based solar cells. of technical features, Chapter news, alumni notes, etc. If you enjoy this In this issue, we review applications of organic and inorganic issue, please check out the archive index of prior features on page 39. semiconductors that can be used in photovoltaic devices. The concept The editorial board can be contacted by e-mail at [email protected]. of metal-semiconductor junction is introduced and explained from both Dr. Steve modeling and simulation perspectives, as well as the practical device E. Watkins fabrication viewpoint. Metal-semiconductor junctions have shown great promise in replacing current p-n junction solar cells. In other words, a Gamma Theta Chapter simpler and more cost-effective fabrication process, in addition to the potential to achieve higher power conversion efficiency, have made metal-semiconductor junction solar cells an attractive choice for use in developing markets and economies. It is the objective of this issue to demonstrate global efforts being made to study new materials and structures that can be used in solar cells to achieve higher efficiency and easier production.

Bell Solar Battery

THE BRIDGE HKN.ORG 5 Editors-in-Chief Guest Editors

THE BRIDGE, May 2021 Letter from Letter from the Editors-in-Chief the Guest Editor

Bell Solar Battery

THE BRIDGE HKN.ORG 5 Chapter News Chapter News

called Space Makers. The program promotes student The group has also seen the strong need to IEEE-HKN Consolidating Student participation in inspiring and interactive learning promote STEM initiatives and is implementing a experiences to address challenges and to develop women-only program for its members called Space Debuts Successful Groups to Strengthen disciplinary and cross-disciplinary skills. Girls, with the main objective of addressing the fifth Practices Database Research and Innovation The group initially concentrated in the development sustainable development goal of the United Nations, of satellite systems and communications projects. gender equality. Chapters Officers, Get Inspired Opportunities Space Makers is always seeking new initiatives for the student members. Sometimes those come as short Are you looking for new activities and initiatives to do Submitted by Cesar Vargas-Rosales, Faculty Advisor stays at different companies, or yearlong projects, with your Chapter? Check out our Successful Practices Lambda Rho Chapter, Tecnologico de Monterrey, Mexico such as AztechSat II nanosatellites with NASA, or the Database! Using the activity reports submitted by our Intercollegiate Rocket Engineering Competition (IREC). Chapters, IEEE-HKN has constructed a searchable The Lambda Rho Chapter of IEEE-HKN together with One of these initiatives was the SPES Project, where and sortable database of activities for programming, the IEEE ComSoc Monterrey Chapter have focused on the group participated in a worldwide competition recruiting, fundraising, and community service ideas creating a constructive and nurturing environment for organized by Airbus and UNOOSA with a design of that is available to all Chapter leaders. Only current undergraduate and graduate students at Tecnologico a space mission for a 3-unit CubeSat that aimed Chapter leaders can access the database, so be sure de Monterrey in Mexico. to dock in the Bartolomeo module located in the to update your Chapter Officers and Advisors. One initiative has been the organization of students International Space Station (ISS). The nanosatellite in dedicated groups with hands-on activities for design was made from scratch, and it was extremely Volunteers, Here is a New research and innovation. This is mutually beneficial: challenging. The students developed their research Opportunity for You First, it creates an environment where students can abilities and skills for organization, teamwork, positive develop their own abilities and skills; and second, it Interested in helping build up the database? leadership, effective communication, problem-solving, gives researchers a chance to develop solutions to Figure 2. Hands-on action and design We are currently seeking volunteers to review and critical thinking, and working under pressure. The work format activities! To find out more, read the position problems with practical character. In any case, the The group participated with project proposals for was based on procedural learning with the method of description and fill out the Reviewer Application. initiative helps promote the IEEE-HKN Chapter, the the Mexican Space Agency in 2019. Also, the group lean start-up. group, and the projects throughout the academic developed an organization of its own, with three Currently, Space Makers is working with Keysight community resulting in an increased interest in basic areas: Satellites, Rovers and Rocketry. Mentors Technologies for a pilot group to get a certification participating in the group. from industry or academia, even from international in IoT this year. The final goal is to have an IoT At Tecnologico de Monterrey, we have worked for companies or organizations, are part of each area. certification within the senior year of the Electronics three years to establish, implement, and consolidate Space Makers established contacts with CONAE Engineering undergraduate program by 2022. a group of students and professors into a program Argentina, NASA, Samara University in Russia, and IEEE Learning Content Japan to create opportunities toward potential at Your Fingertips graduate programs and research stays. Check out the IEEE Learning Network (ILN) for hundreds of hours of online learning courses from across IEEE, taught by industry experts Visit iln.ieee.org and start learning today!

Stay up to date with the latest discounts: innovationatwork.ieee.org/whats-new Figure 1. Founders of Space Makers and Mixcoatl Project members (video in Spanish https://www.youtube.com/watch?v=KfPVefXeb0g) Figure 3. Development of CubeSat for Project Bartolomeo

THE BRIDGE HKN.ORG 7 Chapter News Chapter News

Toy Adapt-a-thon Uses Basic Circuit Knowledge Mu Beta Chapter’s Kidzineers STEM Outreach Program to Create Holiday Joy Submitted by Heba Shaban, Faculty Advisor Mu Beta Chapter, Arab Academy for Science, Technology & Maritime Transport (AASTMT) Submitted by Jerika Cleveland, Chapter President Gamma Tau Chapter, North Dakota State University The Mu Beta Kidzineers program was recently launched by IEEE-HKN Mu Beta Chapter members as In the final months of 2020, members of the Gamma a STEM outreach program for pre-university students. Tau Chapter at North Dakota State University became The program aims to provide mentoring to pre- elves who hack as they worked with the university’s university students as well as educational activities Disability Services department to modify electronic and competitions. Our goal at the Mu Beta Kidzineers toys for children with special needs. program is to give pre-university students the chance The Chapter’s first ever Toy Adapt-a-thon, where to learn, collaborate with their peers, and pursue engineers created audio jack connections in parallel their careers. Being a part of IEEE-HKN, we also aim Mu Beta Chapter members holding the outstanding chapter plaque and key chapter recognition to the buttons on toys, enabled children with motor to promote the goals of HKN, namely, scholarship, disabilities to play like all kids do–by pressing a button. character and attitude. The Mu Beta Kidzineers program is now available on Cleveland said the adaptions are based on basic To jump-start the program, a series of scientific facts the STEM portal of IEEE’s TryEngineering.org website. Through this portal, STEM best practices and programs circuit knowledge: putting an aux plug in parallel to These toys were modified as part of the program was posted weekly to the program’s social media the button on the toy. The aux plug allows for a bigger, pages, where the Chapter’s media team works on are shared with IEEE’s community of volunteers. more accessible button to be attached to the toy that “The Toy-Adaptation is becoming the highlight of unique designs for the posts to make them attractive The Mu Beta Kidzineers program social media pages is activated by children with their fist, elbows, head, HKN- Gamma Tau Chapter’s fall semester,” said to pre-university students. can found here @mubetakidzineers Chapter President Jerika Cleveland, a Ph.D. student, knees, or feet. who led the Chapter’s efforts. “Seeing electrical and computer engineering students, who have finals to 17 MS programs to study for and projects to finish, come together to choose from, plus 4 new adapt toys brings a bit of cheer to the group and 100% online programs department. Walking a dinosaur down the hallways always gets a laugh out of fellow students.” Disability services and teachers who work with disabled children are grateful for the adaptions, Cleveland said: “Making the toys activate with the accessible buttons allows the children to learn how (From left to right) Jerika Cleveland, Henry Wolf, Armin Ekic to interact with the world. As the children get older, With this modification, the expensive buttons, which the big buttons will help the children interact with Learn more: cost US $60 to US $100 each, can be removed from computers and assistant devices. This may provide go.tufts.edu/engmasters one toy and used with multiple toys, saving families independence and a voice to them as they grow up, money by being able to use fewer buttons. so learning how to use the buttons early is important.” PhD, certificate, and postbac programs also available The Chapter also adapted the toys for free (with If you would like to learn more or start your own toy the audio jack, heat shrink, and wiring costing about adaption program, contact Jerika Cleveland. US $2.50). The price of a single adapted toy can To see one of the toys at work, go to EARN A MASTER’S increase by US $30 to US $50 when purchased https://youtu.be/pl6YsqdH-08. through companies. IN ENGINEERING in as little as one year or at your own pace.

THE BRIDGE HKN.ORG 9 Chapter News Chapter News

THE BRIDGE HKN.ORG 9 Donor Profile IEEE-HKN Anniversary You can choose to directly support IEEE-HKN or any of the strategically Are you celebrating a milestone anniversary as an HKN member? identified IEEE initiatives that help meet the world’s most pressing Share your story and photos with the entire IEEE-HKN family. challenges and help us to realize the full potential of IEEE. Submit a paragraph or two about your journey and photos of yourself participating in HKN activities or of your HKN memorabilia. Your submission will appear in a future issue of THE BRIDGE or in our Alumni Newsletter. Email us to learn more and to share your story.

Harnessing Strength in Numbers Congratulations, John McDonald, As a member of the American Institute of Electrical Engineers (AIEE) and IEEE-HKN for 50 Years The Institute of Radio Engineers (IRE)–organizations which ultimately evolved into IEEE in 1963–IEEE Life Fellow Dr. Lyle Feisel has enjoyed John McDonald, P.E., Smart Grid Business Development Leader for GE’s the benefits of his IEEE affiliation for more than 60 years. Grid Solutions business, is an exemplary IEEE-Eta Kappa Nu member who Lyle Feisel, demonstrates how to pursue excellence in all areas. John has published 150 John McDonald, “The student branch gave us opportunities to socialize with faculty and papers and articles, co-authored five books, has one US patent, and has held other students and gain insight into the actual practice of engineering, Ph.D. countless leadership positions in different organizations. P.E. and the networking and technical information I received were so helpful,” IEEE Life Fellow said Dr. Feisel, who served on the HKN National Board from 2003 to The quest for academic and professional excellence needs to be coupled Smart Grid Business Nu Chapter 2006.. “The camaraderie and friendships that developed over the years with the pursuit for relationship excellence, he says. One way to pursue Development Leader, GE are some of my fondest memories of being an IEEE member.” relationship excellence is by constantly looking for ways to give back. Iowa State University “We can always find the time to do what we want to do,” he says. “No Beta Chapter, 1971 Dr. Feisel attributes his decision to donate to such initiatives as the matter how busy I am, I will find time to help others succeed.” Purdue University IEEE-Eta Kappa Nu (IEEE-HKN) Fund, the IEEE Foundation Fund, the IEEE Dr. Lyle Feisel, pictured with his wife, John is a dedicated volunteer with IEEE-HKN, serving on the Strategic Dorothy, donates to IEEE-Eta Kappa Nu History Center Fund, and the IEEE Life Members Fund, to “the recognition Planning Committee. Through IEEE-HKN, he says he is able to inspire others (IEEE-HKN) Fund, the IEEE Foundation that there are many needs out there and that our contributions can Fund, the IEEE History Center Fund, and and encourage them in their professional journey by being a role model help meet them,” he said. “My wife and I have also included the IEEE the IEEE Life Members Fund. who leads others by his actions, not just his words. In fact, he recently gave Foundation in our estate plan because you can’t take it with you, so why of his time again by offering a session on the “12 Key Insights to Career not have it used for something you believe in? The IEEE Foundation is Management” at IEEE-HKN’s Pathways to Industry program. You may watch a very efficient and effective charity that will make good use of it by following this link. any bequest.” He says he enjoys giving back to Eta Kappa Nu because of the reinforcement “The critical function of the IEEE Foundation–or any charity–is that it lets and confidence he received when being inducted as a student in 1971. you help accomplish a goal that you could never achieve by yourself,” As he thinks over his years in industry, he realized: “I’ve come to the point in Dr. Feisel explained. “Acting alone, we could never put a girl through high my career where I’ve already had plenty of awards and recognition, I don’t school in Guatemala, teach a class in New Jersey about the history of need that anymore. My greatest satisfaction is helping a young person be engineering, illuminate a light bulb in Haiti, or take a kid for a ride on a successful themself, and when they achieve success, seeing how happy replica sailing ship. By giving to the IEEE Foundation and other charities,” they are and knowing I had something to do with that. What really drives he said, “we’re able to help do all of those things.” me today is to help other people.” John is an IEEE Foundation Director, and has served on the Board of Governors of the IEEE-SA (Standards Association). He is Past President of the IEEE Power & Energy Society (PES), the Past Chair of the IEEE PES Substations Committee, and the IEEE Division VII Past Director. Are You Eta Kappa Nu? John, a Life Fellow of IEEE, was awarded the IEEE Millennium Medal, the IEEE Show Your Eta Kappa Nu! Power & Energy Society Excellence in Power Distribution Engineering Award, If it’s not on your card, it’s not in your IEEE membership record. Let us know! the IEEE PES Substations Committee Distinguished Service Award, and the IEEE PES Meritorious Service Award. 800-406-2590 www.hkn.org [email protected] Congratulations, John! We thank you for all you have given to the IEEE-HKN family.

THE BRIDGE HKN.ORG 11 Donor Profile IEEE-HKN Anniversary You can choose to directly support IEEE-HKN or any of the strategically Are you celebrating a milestone anniversary as an HKN member? identified IEEE initiatives that help meet the world’s most pressing Share your story and photos with the entire IEEE-HKN family. challenges and help us to realize the full potential of IEEE. Submit a paragraph or two about your journey and photos of yourself participating in HKN activities or of your HKN memorabilia. Your submission will appear in a future issue of THE BRIDGE or in our Alumni Newsletter. Email us to learn more and to share your story.

THE BRIDGE HKN.ORG 11 Award Spotlight ECEDHA Corner

panel as part of ECEDHA’s Educators Summit in Congratulations, 2019-2020 ECEDHA and December of 2020. You may view the panel on demand. Outstanding Chapter Award Winners! IEEE-HKN Partner for • ECEDHA + IEEE-HKN = Recipe for Success, a town hall event that presented several case studies of The IEEE-Eta Kappa Nu (IEEE-HKN) Board of The 2019-2020 Outstanding Chapter Student Success successful partnerships, highlighted the service Governors is excited to announce the Outstanding Award recipients are: component of HKN, and how Department Heads Few organizations have the synergy and alignment Chapter Award winners for the 2019-2020 can achieve their objectives for student success Alpha University of Illinois at like IEEE-Eta Kappa Nu and The Electrical and academic year. and outreach in their campus communities. Urbana-Champaign Computer Engineering Department Heads Association The three Town Hall sessions are available on the The 21 Chapters recognized represent the top 15 (ECEDHA). The challenges of preparing, engaging, Beta Purdue University IEEE-HKN YouTube channel: percent of the Chapters worldwide. The Outstanding inspiring, and involving students is best met when Beta Epsilon University of Michigan, • Session 1 IEEE-HKN: Not Just Another Chapter Award (OCA) recognizes excellence in IEEE- Department Heads and HKN Chapters work together. Ann Arbor Student Organization HKN Chapters for their activities. That is why the two organizations have a long history Beta Eta North Carolina • Session 2 IEEE-HKN Impact: How Your of working together to meet the needs of our Chapters. The award is based on the content and description State University Department Will Benefit from Your HKN Chapter of Chapter activities that are contained in the Annual Beta Theta Massachusetts Institute ECEDHA is the premier academic association of its • Session 3 Enhancing Student Life & Chapter Report, which summarizes the Chapter’s of Technology kind encompassing all major electrical engineering, Peer-to-Peer Community activities from the previous academic year. Delta Omega University of Hawaii at Manoa computer engineering, and related programs at universities across North America. ECEDHA’s mission The ECEDHA Summit Series Epsilon Delta Tufts University For the purposes of this award, emphasis is is to foster advances in the disciplines of electrical presents virtual programs organized on service activities to the department, school, Epsilon Eta Rose-Hulman and computer engineering, facilitate interaction by ECEDHA leadership and offered community and Chapter. Equally important is Institute of Technology and exchange of ideas among its members, and to ECE educators on a quarterly basis. The summits provide a forum for peers to gather, promoting the goals of IEEE-HKN by inducting Epsilon Omicron University of Delaware improve communication with the profession, industry, learn, and share best practices addressing common as many eligible undergraduate students, graduate Iota Gamma University of California, government, and other communities of interest. challenges. Each two-day summit focuses on a subject Los Angeles students and faculty in the IEEE designated technical In just the last six months alone, IEEE-HKN and area of particular interest to the ECE community, such fields of interest as possible and by participating in Kappa Psi University of California, ECEDHA have collaborated on three programs: as the Educators Summit in December. IEEE-HKN student Chapter projects. San Diego • ECEDHA and HKN: Partnering for Student Success, If you would like to learn more about ECEDHA, Each recipient Chapter will be recognized at the Lambda Tau University of Puerto Rico a one-hour learning session held during the 2020 including information on the next Summit Series, 2021 IEEE-HKN Graduation Celebration scheduled at Mayaguez HKN Experience last November. It is available to visit www.ecedha.org. You may also contact watch on demand. for 2 p.m. (EDT) on 5 June. They also will receive an Mu University of California, Megan Bekolay, Program Director, ECEDHA, engraved plaque. Berkeley • Lessons Learned: Student Insights on Fall 2020, at [email protected]. Mu Alpha UCSI University in which two IEEE-HKN students participated in this Congratulations to the honorees and thank you all Kuala Lumpur for your service to IEEE-HKN, your university and Mu Beta Arab Academy for Science & your community. We hope you will join us at the Technology - Alexandria Alvaro celebration on 5 June. Register here. Sahagan, Mu Nu Politecnico Di Torino 2021 Outstanding Student Award 2020 Award Mu Rho Valparaiso University Applications Due 30 June Winner Mu Tau Waseda University Nu Iowa State University The Alton B. Zerby and Carl T. Koerner Outstanding Student Award recognizes outstanding scholastic excellence and high moral character, coupled with Sigma Carnegie-Mellon University Olivia Zeta Delta University of Texas at El Paso demonstrated exemplary service to classmates, university, community, and country. Hsu, 2019 Each Chapter may nominate one member for this award each year. Award Who will you Chapter nominate? Winner Applications are due 30 June 2021 LEARN MORE

THE BRIDGE HKN.ORG 13 Award Spotlight ECEDHA Corner

THE BRIDGE HKN.ORG 13 Feature Feature Modeling of organic semiconductor conduction parameters with reference to inorganic semiconductors

It is found that the semiconductor parameters could be the same in both classes of semiconductors but their mathematical formulations and range of values are different. The semiconductor properties and parameters treated in this paper are: • The organic semiconductor atomic arrangement • Arrangements of molecules in the organic materials Figure 1: Typical molecular structures leading to OSC materials. Top, from left: pentacene, α-sexithiophene (α-6 T), poly(3-hexylthiophene) or P3HT. • The energy band structure of the organic semiconductor Bottom, from left, copper phthalocyanine, naphthalenetetracarboxylic • Carriers in equilibrium in the organic semiconductor diimide (NTCDI), terthiophene tetracyanoquinodimethane. The first four • The doping of the organic semiconductors are hole carriers, and the last two electron carriers. • Current conduction in organic semiconductors • Recombination of mobile charge carriers in heteroatoms and appending vast libraries of side chains organic semiconductors that enable tuning of charge transport, processing • The semiconductor equations conditions, and chemical interactions [2].

The organic semiconductor atomic arrangements Arrangements of molecules in the organic materials The arrangements of the atoms inside the material Modeling of organic semiconductor control its physical properties including the electronic As the organic materials are composed of organic and optical properties. The atomic arrangements molecules, then the geometrical arrangement of the conduction parameters with reference depend on the chemical bonding between the molecules in the materials affects much its electronic constituting elements of the material and their and optical properties as they define the intermolecular electronic configuration. interaction. This issue is similar to the formation of to inorganic semiconductors crystalline structures in inorganic semiconductors. The organic semiconductors are compounds having By Abdelhalim Zekry, W. Abdelaziz atomic arrangement patterns as the organic materials. So, one can consider that the organic semiconductor is The authors are with the Department of Electronics and Electrical Communications, Faculty of Engineering, Ain Shams The main feature of such a structure is that it is a basically a fine-grained semiconductor with a molecule University, Cairo, Egypt (e-mail: [email protected]; [email protected]). molecular one with strong covalent bonds inside the representing a grain. The charges can move easily molecules and weak inter molecular bonding mostly by inside the molecule as consequence of its extended Abstract van der Wall forces. So, the organic semiconductors are valence structure, but at the molecule boundary there will be potential barriers that impede the motion of This paper shows how the electronic properties of into two subgroups, the pigments, which are not soluble composed from organic molecules arranged randomly the charge carriers. So, it is clear that the transport of organic semiconductors can be described in the same in organic solvents, and dyes, which are soluble. As a or regularly or in a mixed fashion. charges between the molecules is the limiting factor way as the inorganic semiconductors. This is required result of their chemical properties, polymers can be Figure 1 shows the atomic configuration of typical for this movement. This is similar to the transport for exploiting the existing electron device simulators solution processed whereas small-molecule materials organic semiconductor molecules. One sees that across the grain boundary in metallic semiconductors. in solving also the organic semiconductor devices. must be in general thermally evaporated. thanks to the presence of the carbon atoms in the Many research efforts are spent to control the In addition such a description will make such important Studying the properties of organic semiconductors helps molecules of the organic semiconductors, the bond intermolecular interaction to ease the motion class of materials easier to understand. in utilizing them efficiently to innovate new electronic in the molecule core is covalent like that of metallic across the molecules of materials by controlling Introduction devices. If these properties are referenced to inorganic silicon semiconductor. It is also noticed that all bonds their molecular arrangements during the deposition semiconductors [1], then they can be considered as their in the molecules are saturated and therefore the Organic semiconductors can be broadly divided into process. The arrangement of the molecules ranges extension. As there is a wealth of computer aided analysis intermolecular bonding will be of van der Waal dipolar polymers and small-molecule materials. There are notable from regularly ordered molecules to randomly and design tools for the inorganic semiconductors, bonding which is weak. differences from a chemical point of view between these ordered molecules [3]. Figure 2 depicts some of then one can apply them also for the modeling and Therefore, we find that these materials are highly ductile two classes, affecting their technological performance. these arrangements. Polymeric macromolecules are composed by the simulation of the organic semiconductors with the proper and classified mechanically as plastic materials. So, they Progress in fabrication, particularly solution processing, repetition of a fundamental unit, called the monomer, modifications to account for the properties of the organic have different mechanical properties from the metallic and characterization of small-molecule and polymer and are soluble in organic solvents. Accordingly, they can materials. So, in this paper the organic semiconductors semiconductors such as silicon which is hard and stiff. organic semiconductors could enhance these materials be processed in liquid form. Small-molecule materials, are modeled as their inorganic counterparts. The model There are thousands of possible variations in these and utilize them in industrial products such as organic termed also molecular materials, can be further divided similarities and differences are pointed out. structures, including substitution of some carbons for

THE BRIDGE HKN.ORG 15 Feature Feature Modeling of organic semiconductor conduction parameters with reference to inorganic semiconductors

THE BRIDGE HKN.ORG 15 Feature Feature Modeling of organic semiconductor conduction parameters Modeling of organic semiconductor conduction parameters with reference to inorganic semiconductors with reference to inorganic semiconductors

field effect transistors (OFETs) and light emitting The DOS of the organic materials is Gaussian while Organic semiconductor materials have relatively potential of the doping molecules where the doping diodes (OLEDs) playing an increasingly important that of the inorganic is a square root function of energy higher energy gaps compared to the most common level is lying under the LUMO level by ionization energy

role in modern technology. Further advantages of difference from the band edge. semiconductor metallic material, e.g. silicon (Si). The Eid=EL-ED. organic semiconductors compared to conventional effective density of states according to the data in In a doped material, to determine the Fermi level one silicon-based materials include mechanical flexibility, the literature are not much different from those of uses the mass action law and the neutrality equation as lightweight and easy and inexpensive solution process silicon, therefore, the intrinsic concentration of the in the metallic semiconductors such that the following ability. Continuous refinement of design strategies and organic materials is very small. Accordingly, organic relations hold: fabrication techniques allowed them to now routinely materials approach the insulators rather than the display impressive charge carrier nobilities of over 1 semiconductors. In this sense, practically in their The neutrality equation n= Nd+ + p, Where Nd+ is cm2 V–1 s–1, reaching as high as 20–40 cm2 V–1 s–1 in intrinsic state they behave as an insulator. concentration of the ionized donor molecules. 2 –1 –1 2 single crystals and even hundreds of cm V s in Regarding the purity of the materials, metallic The mass action law np= ni , the Fermi Dirac Figure 3: Density of states (DOS) as a function of the energy (E) for ultrapure samples at low temperatures. distribution function Nd+ = Nd f(Ed), metallic and organic semiconductors. semiconductor is produced with high purity but the organic semiconductors are produced with less purity Where; The effective density of state assumes that the density and they contain impurities leading to make them of states is located at the positions of Ec, and Ev as well either p-type or n-type conducting. as EL, and EH, respectively as depicted in the same Once doped either intentionally or unintentionally one Similar equations hold for the acceptor molecules. figure. Finally, the energy level diagram of the organic can define for them a Fermi level as in the metallic semiconductor is shown in Figure 4, where is the material. Otherwise, one describes them as insulators, Current conduction in organic semiconductors electron affinity, Ef is the Fermi-level, Eg is the band gap in the sense that their energy levels are aligned to the The current conduction mechanisms in metallic χ and is the work function of the materials. vacuum level. If the material is doped, the energy levels semiconductors are also applicable in the organic So, formally the energy band diagram of organic through a system of materials are aligned to Fermi level semiconductors. The common current mechanisms φ semiconductor is similar to that of inorganic at thermal equilibrium. in both types of semiconductors are the drift and the Figure 2: Typical aggregates and crystal packing motives of the semiconductor [4]. diffusion currents. The mobile charge carriers can drift π-conjugated cores: (A) lamellar π–π stacking motifs with one- The doping of the organic semiconductors dimensional charge carrier channel, (B) brick-stone or brick-wall (also under the influence of the applied electric field and can Carriers in equilibrium in the called β-sheet) arrangement with two-dimensional π–π stacking; (C) The doping of the metallic semiconductors is by also diffuse under the concentration gradients. The drift γ-packing with slipped face-to-face π–π stacking; (D) herringbone face-to- organic semiconductor atomic substitution while in the organic material it is current Jdrift can be expressed by the known relation as edge packing without face-to-face π–π overlap. The intrinsic concentration ni by adding doping atoms or doping molecules. The in (3): Generally, in any semiconductor there are two types of doping by atoms is inferior than doping by molecules The energy band structure of the Where E is the intensity of the electric field,q is mobile charges: the electrons in the conduction band as the doping by atoms results in unstable materials organic semiconductor and the holes in the valence band. If the material is [6]. The organic materials can then be doped by As the organic materials are composed of molecules adding molecules where one gets n-type and p-type pure and intrinsic the source of the electrons and holes the electronic charge, n and p are the mobility of weakly bound to each other therefore, the energy will be the thermal generation of electron hole pairs. conduction. In case of doped organic semiconductor electrons and holes, respectively and n and p are the band structure will be that of the molecules with The concentration of the electrons will be equal to that one can define a Fermi level for the materialE f such electron concentrationμ and theμ hole concentration, limited splitting of the energy levels to form narrow that one can express the electron concentration by a of the holes n0=p0=ni according to the mass action law, respectively. 2 2 bands. The energy band structure was investigated n0 p0=ni [5]. The intrinsic concentration is given by; ni = relation similar to that of the inorganic materials such The mobility is different from that of the metallic using the density function theory. It is found that NCNv exp(–Eg/KT), where K is the Boltzmann constant that the electron concentration n can be expressed as semiconductors because of the nature of the organic valence and conduction bands are formed with and T is the absolute temperature. This law is general in (1)a : semiconductors.μ Here the electrons hop across Gaussian distribution of the density of states around and applicable for all semiconductors. potential barriers from a molecule to its neighboring the conduction band edge Ec= EL, the LUMO level one. The depth of the potential barriers is randomly and the valence band edge the HOMO level. Ev= EH. The same holds for the p-type organic semiconductor The conduction band and the valence band have distributed around certain average value. It results such that the hole concentration p can be written as: that the mobility will be dependent on the applied effective density of states Nc and Nv, respectively. This description of the energy band structure is similar to electric field and the temperature in an activated that of the inorganic semiconductors. transport process. Specifically, the mobility increases by In case of n-type the donor molecule gives an electron increasing the electric field and temperature [7]. A typical density of state DOS(E) as a function of the to the host molecules and it becomes a positive ion energy E is shown in Figure 3 for an organic material which is considered immobile similar to the doping in and inorganic semiconductor for sake of comparison. Figure 4: The energy level diagram of the organic semiconductor. the metallic semiconductor. There is also an ionization

THE BRIDGE HKN.ORG 17 Feature Feature Modeling of organic semiconductor conduction parameters Modeling of organic semiconductor conduction parameters with reference to inorganic semiconductors with reference to inorganic semiconductors

The other current that can exist in the organic material through trap levels in the bandgap. These trap REFERENCES is the diffusion current when concentration gradients levels are called recombination centers. The most [1] Zekry, A., Shaker, A., Salem, M., 2018. Chapter 1 - solar cells and of electrons and holes can be formed. The diffusion dominant non-radiative recombination mechanism And arrays: principles, analysis, and design, Advances in Renewable Energies and Power Technologies, first ed., Yahyaoui. current Jdiff has the well-known expression: is that of the Shockley-Read-Hall. It exists in all semiconductor materials. [2] Eric F.V. Scriven and Christopher A. Ramsden, “Chapter Five - Heterocyclic Building Blocks for Organic Semiconductors”, Advances in Every recombination mechanism has its specific The continuity equation for holes in one dimension Heterocyclic Chemistry, vol. 121, pp. 133 - 171, 2017. Where Dp and Dn are the diffusion constants of the dependence on the hole and electron concentrations can be written as: [3] Gryn’ova G, Lin KH, Corminboeuf C., “Read Between the Molecules: holes and electrons, respectively. The concentration and its rate constants. For more details on such Computational Insights into Organic Semiconductors”, J. Am Chem. Soc., gradients dp/dx and dn/dx are of holes and recombination mechanisms, please refer to the ref. [5]. vol. 48, pp. 16370-16386, Nov. 2018. electrons, respectively. [4] Jin-Peng Yang et al, “Origin and role of gap states in organic There is a specific recombination mechanism which semiconductor studied by UPS: as the nature of organic molecular The diffusion coefficientD is related to the mobility exists in the organic semiconductors. It is the Langevin Where p is the hole concentration, Jp is the hole crystal”, J. Phys. D: Appl. Phys, vol. 50, pp. 423002, Oct. 2017. μ by the Einstein relation: which occurs as direct consequence of an electron current density, p0 is the hole concentration at thermal [5] Abdelhalim zekry, “Electronic devices with physical insight”, LAP and hole comes in the field of the other in a low field equilibrium, τp is the hole lifetime and ge is the external LAMBERT Academic Publishing, 2019, 272 pages. mobility materials. They get this chance when they generation rate that may be affected by suitable [6] Lüssem, B., Riede, M. and Leo, K., “Doping of organic semiconductors”, Phys. Status Solidi A, vol. 210, pp. 9-43, Dec. 2012. Where Vt is the thermal voltage. meet while moving. Its recombination rate rlv can be incident photon flux. expressed by [8]. A similar continuity equation can be written [7] Mandoc, Maria Magdalena, “Device physics of all-polymer solar cells”, There is also the space charge limited current SCLC s.n., 134 p, 2009. when the electric conduction is affected by single type for electrons: [8] Holst, van der, J. J. M., Oost, van, F. W. A., Coehoorn, R., & Bobbert, P. charges either electrons or holes. A.,” Electron-hole recombination in disordered organic semiconductors : Where, is the permittivity. It is found that this The SCLC will be treated in detail when dealing with validity of the Langevin formula”, Physical Review B, vol. 23, pp. 235202- mechanism is applicable in case of the organic LEDs, 1/8, 2009. the conduction in metal organic semiconductors ε while it must be reduced by an appreciable factor Where, Jn is the electron current density, τn is the carrier diodes. The space charge limited current prevails when Abdelhalim Zekry is a professor when applied to organic solar cells. Generally, the lifetime of electrons n0 is the electron concentration the conduction is unipolar in originally semi insulating of electronics at the Faculty of rate can be expressed by rlv=kr pn , where kr is the at equilibrium. These equations can be formulated materials with very low mobility. recombination rate constant that can be determined Engineering, Ain Shams University, in three dimensional forms. One simply uses napla Egypt. He has worked as a staff This state is presented in the intrinsic organic materials experimentally. operator for time rate of change of the carriers and member at several universities. injected by either electrons or holes from metallic A quantity which can be used to characterize the gradient one uses the div operator. He has published more than 300 electrodes. It is observed many times in such semiconductor materials is the minority carrier lifetime papers. He also has supervised organic materials. Conclusions more than 110 Master’s theses τ which is defined by:τ=dn ⁄ U n [5], where Un is the and 40 Doctoral Dissertations. In this paper we showed clearly that one can Recombination of mobile charge carriers excess recombination rate for the electrons and dn is Prof. Zekry focuses his research programs on the field assign the same material parameters to inorganic in organic semiconductors the excess electron concentration. of microelectronics and electronic applications including semiconductors as organic semiconductor materials. communications and photovoltaics. Recombination is the disappearance of a mobile The semiconductor equations One can assign for them, an effective mass, a He has been awarded several prizes for his outstanding electron in a hole. This process leads to the loss of The semiconductor equations [5] are also applicable mobility, a diffusivity, an energy gap, a Fermi level, research and teaching performance. mobile charge carriers and thereby affects much the for the organic semiconductor as they are of general doping concentrations as well as same recombination Walaa Abdelaziz is a teaching electrical characteristics of the semiconductor devices formulation. These equations are the, the poison equation, mechanisms. The major differences are in the assistant at the Modern Academy, including solar cells and light emitting diodes. the current equation, and the continuity equations. numerical values of these parameters. In addition, Egypt. She graduated from Ain there may be additional recombination mechanisms Shames University in 2005 and The recombination mechanisms were studied These equations can be formulated as: intensively in metallic semiconductors [5] and to less because of the very low mobile carrier mobilities in earned her Master’s degree in 2012 organic materials. from Cairo University. She focuses extent in the organic semiconductors. her research on renewable energy, From the conceptual point of view, the recombination With ρ is the charge density and D is the electric The most important conclusion is that one can use the especially solar cells. mechanisms occurring in the metallic semiconductor displacement. same simulators intended for the inorganic devices also occur in the organic semiconductors. These to the organic semiconductor devices. This will save mechanisms can be classified into radiative and tremendous efforts to develop new simulators for the + - non-radiative types. Radiative recombination is a Where, Nd and Na are the ionized donor and acceptor organic semiconductor devices. consequence of the direct fall of electrons from the molecules concentrations. The current equations can conduction band to the valence band while the non- be written in the form: radiative one when the fall of the electrons occurs

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THE BRIDGE HKN.ORG 19 Feature Feature Modeling organic semiconductor metallic contact and optoelectronic parameters with reference to inorganic semiconductors

Conduction in Metal Organic Semiconductor Metal MOSM Diodes The first challenge for determining the current of the MOSM Diode is the energy alignment at the metal organic semiconductor interface. When the semiconductor material is doped then one can define for it a Fermi level and accordingly the Fermi level will be constant at the interface similar to the metal- inorganic semiconductor. In case of intrinsic organic semiconductor, it behaves Figure 1: Energy level diagram a) before contacting MOSM diode and b) as an insulator because of the relatively large bandgap at equilibrium; the dotted line refers to energy level diagram at applied and the amorphous nature of the material. In this case, voltage Va. the energy alignment will be according to the vacuum metal work function φk and the electron affinityχ , that is: energy level. That is at equilibrium the energy levels align themselves to the vacuum level, Evac. Such simplifying assumptions can facilitate the derivation of mathematical The current will be limited by the thermionic injection expressions for the currents. from the metal that can be expressed by the well Inspecting the literature concerned with the currents known relation: Modeling of organic semiconductor in the MOSM diodes with one charge type, it is found that the current can be either injection limited from the metallic contact and optoelectronic M-S contact or it can be space charge limited inside the With A = ,where φ= φb, m is the effective mass semiconductor itself. The space charge limited current and h is the Planck constant. parameters with reference to exists when it is much less than injection current. The The origin of the space charge limitation is very low injection current is limited by the height of the injection mobility of the organic semiconductors and the unipolar inorganic semiconductors barrier at the contact which is more or less independent behavior in addition to the relatively low electric field. of the applied voltage except the image force barrier Accordingly, during their flow inside the material the By Abdelhalim Zekry, W. Abdelaziz lowering and equal to the difference between the work charge carriers accumulate in it and build space charge function of the metal and the electron affinity of the The authors are with the Department of Electronics and Electrical Communications, Faculty of Engineering, Ain Shams that impedes the motion of the charges from the injector organic semiconductor. University, Cairo, Egypt (e-mail: [email protected]; [email protected]). to the injecting contact to the collecting contact. It is required to determine the factors limiting the current The space charge limited current is well known from the Abstract in the MOSM diode under the assumption of single transport of electrons in vacuum and it is termed the charge type injection in the organic semiconductor. This paper will show how the metal organic Also, the optoelectronic properties of the organic three halves power law where the current is proportional That is the metal can inject either electrons or holes in semiconductor junctions differ from those of the semiconductors will be described as they have to V3/2, where V is the voltage across the diode. It also the organic semiconductor. Basically the current can be metal inorganic semiconductor contacts. In such applications in optoelectronic devices. exists in the conduction by insulators, but with injection limited or space charge limited. In each case the contacts the current flow is normally space charge other forms. Then specific functional organic semiconductor I-V relationship of the diode is completely different. limited. In addition, optoelectronic properties are materials will be addressed to show how the organic For a 1D trap-free solid, the corresponding SCL current Now let us describe the current of the MOSM diode also modeled and the differences from the inorganic semiconductor can perform specific functions in the density is known as the Mott–Gurney (MG) law [1], when it is limited by the potential barrier between the semiconductors are made clear. The idea of functional electronic organic devices specially the solar cells. given by: organic semiconductors is introduced and examples of metal and the organic semiconductor. Figure 1 shows the such materials are given. So, the topics covered in this paper are: energy band diagram before contacting the diode layers • Conduction in metal organic semiconductor metal and after contacting. Introduction Where εr is the relative permittivity of the solid. If the MOSM diodes. Assuming that the energy level alignment will be the In order to access the organic semiconductor electrically • Optical properties. solid has an exponentially distributed traps (in energy), vacuum level, then at the metal semiconductor contact it is known as the Mark–Helfrich (MH) law, or the one has to supply it with metallic electrodes. So, the • Functional organic semiconductors. of the cathode, a potential energy difference between trap-limited SCL current density JMH; metal organic semiconductor junction is a basic structure the metal and the organic semiconductor will be formed deserving detailed study. that can be expressed by the difference betweenφb the

THE BRIDGE HKN.ORG 21 Feature Feature Modeling organic semiconductor metallic contact and optoelectronic parameters with reference to inorganic semiconductors

THE BRIDGE HKN.ORG 21 Feature Feature Modeling organic semiconductor metallic contact and optoelectronic Modeling organic semiconductor metallic contact and optoelectronic parameters with reference to inorganic semiconductors parameters with reference to inorganic semiconductors

Here, Nc is the effective density of states corresponding Which means that the incident light intensity I(0) at important observation is that of the organic materials to the energy at the bottom of the conduction band, Nt is the surface of the material decays exponentially with rises rapidly to maximum value then decreases again at α the total trapped electron density, and l= Tt/T is the ratio the distance x from the surface. The intensity decays short wavelengths. This absorption coefficient curve can of distributed traps to the free carriers. to (1/e) at x = 1/ α. Therefore, the inverse of α. is the be accounted for by the energy band structure of the The electron traps lie near the conduction band which average penetration depth of the light in the material, organic materials discussed previously in section 3. is here the LUMO level while the hole traps lie near the or may be better named the average absorption length. valence band which is HOMO level. So, in principle there The absorption coefficient depends on the wavelength are hole traps and electron traps that affect electron of the incident light. It is well established now that light α mobility and hole mobility. There are also deep lying is composed of energy quanta called photons. These traps in the energy gap which can act as traps for both photons interact with the electrons and atoms of the material. The photon energy is given by: electrons and holes. Figure 2: Typical I-V characteristic of an organic MOSM diode showing The deep lying traps can act as recombination centers, different mechanism of conduction. wavelength affecting the concentration of electrons and holes; while Figure 4: λTypical shape of the absorption curves of the organic materials The optoelectronic properties of Where h is Planck’s constant and f is the photon compared to silicon the electron traps affect the mobility of one charge type. organic materials frequency. On the other side photons are wave packets For sake of comparison the absorption curve of silicon As for the conduction mechanisms, every one has having a wave length λ, and velocity C = 8 m/s such We are interested in understanding the response of the is plotted on the same graph for the organic materials. its characteristic I-V relation, especially the voltage that C = h f. Therefore, Eph = h (C/λ). The photon energy semiconductor to light, i.e., the photoelectric effect. If It is important to notice that the absorption coefficient dependence and the thickness dependence of the active is inversely proportional to the light wavelength.3 x 10 Now, a light beam is incident on a semiconductor material, of the organic material is much greater than that of material in the diode, D. They can be used as indicators we are in a position to understand how the light affects part of the light energy will be reflected, a part will be silicon. The organic material has a band-pass absorption of the dominating mechanism. the material. Only valence electrons can absorb photons absorbed inside the material after refraction and the characteristic, in contrast to the high-pass absorption when they can acquire sufficient energy to overcome the Then by curve fitting of the current as a function of D, one remaining part will be transmitted. According to the characteristic of the metallic material. The narrow band energy gap of the material. More specifically, photons can determine the physical parameters of the material. energy conservation law: absorption of the organic materials limits it generated One can make additional measurements to verify some can excite an electron from the valence band, causing it photocurrent. Therefore, this property could be considered of the estimated parameters from the fitting such as the to bind with a free hole and create an exciton (italicize inferior to the metallic semiconductors. the word). This process, denoted as photo-generation of I-V measurements. Where I is the incident light energy, and R, A, and T, excitons, is illustrated in Figure 3. The longer-wave length photons with smaller α need In case of doped organic semiconductor either respectively, are the portions reflected, absorbed, a thicker layer of the semiconductor to be absorbed unintentionally or intentionally the material will possess and transmitted. otherwise they can be transmitted across the layer. EL free carries and has a definitive Fermi level. In this case Reflection occurs because of the change of the wave Generally, the minimum semiconductor layer thickness to Eph the material behaves as an ordinary semiconductor and impedance, Zw=√(μ⁄ε) at the surface of the material. absorb light can be expressed by: builds Schottky contacts. The reflectance ρ is given by: Eg In this case the M-S contacts will follow the theory of EH Schottky junctions: This simple relation is of a very critical importance for Figure 3: Photo-generation of excitons solar cell design. As the semiconductors are expensive Where Is is the reverse saturation current, is the ideality Where Zwa is the wave impedance of the air, From Figure 3, the required minimum photon energy one has to use the minimum quantity of them to perform Zwa=√μ0 ⁄ε0. ε is the dielectric constant and µ is ɳ for the photo-generation process Eph Eg. Energy the absorption function. In this concern, one needs the permeability. It is assumed that light is falling factor. For the evidence for these findings please follow rich photons, where e.g., Eph ~ 2 Eg cannot produce thicker crystalline Si-layers as it has the lowest . perpendicular to the surface. For a typical organic the Link in ref. [2]. 2 excitons except with a very small probability≥ as this The required thickness to absorb the incident solar material with equal around; 4 o, and µ= µo = 1/9, α process requires the collision of photons with two valence radiation by organic semiconductors is on the order of one Figure 2 shows a typical I-V curve of an organic which is much less than that of silicon with , an electrons simultaneously if it is a direct process. hundred nanometers. Thin film structures are needed. semiconductor diode. It demonstrates the typical space appreciably largerε than that of theε organic materials., ρ From charge limited current at the intermediate current density. this reflection point of view, the organic materials ρ = 0.3 are The absorption coefficient is a function of the incident Excitons in organic semiconductors In summary, when one applies the voltage on the performing better. wavelength of the photons and it is a material property. As described earlier, incident photons create bound Figure 4 shows typical shapeα of the absorption coefficient MOSM diode the current follows the drift current then The absorption of the light energy is characterized by the electron-hole pairs known as excitons. These excitons of different organic semiconductors as a function of the turns to space charge limited current and then at high absorption coefficient , where have a specific lifetime called the exciton lifetime which applied voltage the current saturates into the thermionic wavelength . The energy gap of the material is also is the time that an exciton lasts on the average before injection limited current. In case of doping the organic α given. It is clear from this figure that materials absorb it disappears by recombination. Because excitons are λ semiconductor the MOSM behaves as a conventional light appreciably only if Eph Eg. A second neutral they move by diffusion inside the molecules Schottky diode. (α > 100/cm) ≥

THE BRIDGE HKN.ORG 23 Feature Feature Modeling organic semiconductor metallic contact and optoelectronic Modeling organic semiconductor metallic contact and optoelectronic parameters with reference to inorganic semiconductors parameters with reference to inorganic semiconductors

where they were created by light. So, the range of their small lifetime of the excitons can reduce the collection Table 1: Examples of organic materials motion is limited by the molecule sizes. It turns out that efficiency of the charge carriers and the high binding the diffusion length of the excitons is about few tens of energy will be subtracted from the net available nanometers in polycrystalline materials [3]. In contrast the potential energy of the collected carriers in case of photo-generated excitons in the metallic semiconductors solar cell applications, in addition the narrow band are readily dissociated by the thermal energy as they are absorption band. weakly bound thanks to the high dielectric screening. Functional organic semiconductors In order to calculate the dissociation energy of the exciton, one can model the electron and its hole in To overcome the previously described functional shortage, the exciton as a modified hydrogen atom as shown in some solutions have been devised by producing specific Figure 5. This model is similar to the hydrogen atom, functional materials. In this section, these functional except that the electron moves with an effective mass materials will be outlined. mn in a medium with a relative dielectric constant r The donor polymer materials instead of r = 1 in a hydrogen atom. Then according to The donor polymer materials are organic ɛ > 1 Bohr atomic model for the hydrogen atom, the required semiconductors with long periodic molecules such ɛ dissociation energy Ei of the exciton can be expressed by: as P3HT. They effectively absorb the incident solar bandwidth. The non-fullerene could be built to have an Conclusions radiation in their absorption range, producing excitons optical absorption curve complementing that of the donor This paper demonstrates that organic semiconductors that diffuse in and across their long-chain molecules material to render the whole donor acceptor complex can be described by the same phenomenological Where mex is the effective mass of exciton composed of and across them. Their long molecules lead to exciton a wideband optical absorber. This led to appreciable parameters as inorganic semiconductors [19], albeit electrons and holes. It is given by: diffusion lengths that are limited to a few tens of increase in the photo-conversion efficiency of solar cells with different mathematical expressions and ranges nanometers, despite being relatively long. [4, 5]. In this case the donor must accept holes and of values. With slight-to-moderate modifications, The acceptor organic semiconductors reject electrons back to perform a role similar to that of simulators for inorganic devices can be used to Where EH is the energy required to ionize the hydrogen the acceptor facilitating the dissociation of the excitons These materials have large affinity to the electrons simulate organic devices. atom. For, metallic semiconductor as silicon, ɛr =12, so generated in the acceptor material. Examples of the such that when they brought in contact to the donor that the dissociation energy is of the order of 0.05eV. acceptor semiconductor are listed in Table 1. Notable points about organic semiconductors While as for an organic semiconductor with a relative molecules, they will attract the electrons of the excitons include the following: formed in the donor materials. So, their LUMO level The transport layers dielectric constant of 4 the dissociation energy amounts • They are molecular in nature, with short-term order; must lie under the LUMO of the donor molecules by an to 0.45 eV. When the effective mass is taken into To produce a built-in field in the active zone of the donor in contrast to inorganic materials, which can have amount of energy greater than the dissociation energy of consideration with the effective mass ratio is greater than acceptor region for further collection of the electrons long-term order in crystallineform. the excitons. In this way they will constitute an effective and holes separated at the donor acceptor interface, one one for the organic semiconductors, the binding energy • They have relatively small mobilities, because of their sink for the electrons of the excitons generated in the contacts the acceptor layer by an electron transport layer or the exciton can be as high as one eV. amorphous nature. donor molecules. They must reflect the holes back to the ETL and the donor layer by a hole transport layer HTL. donor absorber to suppress their recombination in the Both layers must be chosen to be good conveyor of the • Despite being narrow-band absorbers of light, they electron transport layer. electrons and holes to the respective metal electrode. So have high absorption coefficients. • Therefore, they need thin layers to absorb the incident The concept of the acceptor material directly contacting they have to have high conductivity and proper energy light in their absorption band. the molecules of the donor molecules is a basic concept level diagram matching the donor and acceptor layers leading to the efficient dissociation of the excitons. Really and making at the same time ohmic contacts to the • Their dielectric constant is low, leading to excitons it enabled the realization of efficient separation method metallic electrodes. Examples of the HTL and the ETL are with high binding energy. This reduces collection Figure 5: Hydrogen atom model of excitons where they move in a for the generated electron hole pairs in the excitons. By given in the Table 1. efficiency of the charge carriers, which in turn reduces screening medium transferring the electrons of the excitons to the acceptor the net available energy of the solar cell. This high binding energy of the excitons imparts a great molecules its chance for recombination becomes very • This problem has been solved through the use of problem for dissociating the excitons since to collect their small especially when one further transfers the electrons donor and acceptor polymer materials. electrons and holes they must be free. It is now clear that and holes far away from each other by collecting electric In conclusion, despite some shortcomings, organic the good optical properties of the organic semiconductors field. There are two classes of acceptor materials; the materials can be skillfully utilized to create electronic of high absorption coefficient and low reflectance are fullerene and the non-fullerene organic molecules. The devices with unique properties. The road to widespread offset by short lifetime, high binding energy of the fullerene is expensive, less stable in the environment and use of these materials in the electronic industry is long, excitons and narrow band absorption. It is so that the possesses weak optical absorption coefficient with narrow but shows great promise.

THE BRIDGE HKN.ORG 25 Feature Feature Modeling organic semiconductor metallic contact and optoelectronic Modeling organic semiconductor metallic contact and optoelectronic parameters with reference to inorganic semiconductors parameters with reference to inorganic semiconductors

THE BRIDGE HKN.ORG 25 Feature Feature Modeling organic semiconductor metallic contact and optoelectronic parameters with reference to inorganic semiconductors

REFERENCES [1] Zhu,Y. B. and Ang,L. K. , “Analytical re-derivation of space [13] Elizabeth von Hauff, Vladimir Dyakonov, Jürgen Parisi, “Study charge limited current in solids using capacitor model”, Journal of of field effect mobility in PCBM films and P3HT:PCBM blends” , Applied Physics, vol. 110, pp. 094514, Oct. 2011. Solar Energy Materials and Solar Cells, Vol. 87, pp. 149-156, May 2005. [2] Ishii, H., Hayashi, N., Ito, E., Washizu, Y., Sugi, K., Kimura, Y., Niwano, M., Ouchi, O. and Seki, K.,” Kelvin Probe Study of Band [14] hia-Chih Chang, Jhih-Hao Tao, Che-En Tsai, Yen-Ju Cheng, Bending at Organic Semiconductor/Metal Interfaces: Examination and Chain-Shu Hsu, “Cross-linked Triarylamine-Based Hole- of Fermi Level Alignment”, phys. stat. sol. (a), vol. 201, pp. 1075- Transporting Layer for Solution-Processed PEDOT:PSS-Free 1094, May 2004. Inverted Perovskite Solar Cells”, ACS Applied Materials & Interfaces, Vol. 25, pp. 21466-21471, 2018. [3] Mikhnenko, Oleksandr V. and Blom, Paul W. M. and Nguyen, Thuc-Quyen, “Exciton diffusion in organic semiconductors”, Energy [15] Yao, J., Qiu, B., Zhang, ZG. et al., “Cathode engineering with Environ. Sci., vol. 8, pp. 1867-1888, May 2015. perylene-diimide interlayer enabling over 17% efficiency single- junction organic solar cells”, Nat Commun. , Vol. 11, pp. 2726, [4] Eftaiha, Ala’a F. and Sun, Jon-Paul and Hill, Ian G. and Welch, June 2020. Gregory C., “Recent advances of non-fullerene small molecular acceptors for solution processed bulk heterojunction solar cells”, J. [16] Chen, Youchun and Wang, Shan and Xue, Lingwei and Mater. Chem. A, vol. 2, pp. 1201- 1213, Oct. 2014. Zhang, Zhiguo and Li, Haolong and Wu, Lixin and Wang, Yue and Li, Fenghong and Zhang, Fengling and Li, Yongfang, “Insights into [5] Jun Yuan, Yunqiang Zhang, Liuyang Zhou, Guichuan Zhang, the working mechanism of cathode interlayers in polymer solar Hin-Lap Yip, Tsz-Ki Lau, Xinhui Lu, Can Zhu, Hongjian Peng, Paul cells via [(C8H17)4N]4[SiW12O40]”, J. Mater. Chem. A, Vol. 4, pp. A. Johnson, Mario Leclerc, Yong Cao, Jacek Ulanski, Yongfang Li, 19189-19196, 2016. Yingping Zou, “Single-Junction Organic Solar Cell with over 15% Efficiency Using Fused-Ring Acceptor with Electron-Deficient Core”, [17] Liu, Xiang and Chen, Zhiming and Xu, Rongguo and Zhang, Joule, Vol. 3, pp. 1140-1151,April 2019. Ruiwen and Hu, Zhicheng and Huang, Fei and Cao, Yong, ‘Finely Tuned Composition in Conjugated Polyelectrolytes for Interfacial A Review of Schottky Junction Solar Cells [6] Petr P. Khlyabich, Beate Burkhart, Andrey E. Rudenko, Barry C. Engineering of Efficient Polymer Solar Cells”, Small Methods, Vol. Thompson, “Optimization and simplification of polymer–fullerene 2, pp. 1700407, March 2018. By Amirhossein Ghods 1, Chuanle Zhou 1, and Ian T. Ferguson 1,2 solar cells through polymer and active layer design”, Polymer, Vol. 54, pp. 5267-5298, Sept. 2013. [18] W. Abdelaziz, A. Shaker, M. Abouelatta, A. Zekry, “Possible efficiency boosting of non-fullerene acceptor solar cell using This paper reviews recent advances in development I. A Roadmap to Address Global Warming [7] Si Chen, “Dielectric constant measurement of P3HT, device simulation”, Optical Materials, Vol. 91, pp. 239-245, 2019. polystyrene, and polyethylene”, Master’s Thesis / Essay, Chemistry, of high efficiency single and multi-layerp-n junction Renewable energy sources have always received much 2017. [19] Zekry, A., Shaker, A., Salem, M., 2048. Chapter 1 - solar cells and arrays: principles, analysis, and design, Advances in and Schottky junction solar cells. The barrier formed at attention due to their “green” nature, in which they [8] W. Abdelaziz, A. Zekry, A. Shaker,M. Abouelatta, Numerical Renewable Energies and Power Technologies, first ed., Yahyaoui. the interface of a thin conducting film, with a relatively can generate electrical or mechanical power without study of organic graded bulk heterojunction solar cell using SCAPS simulation, solar energy, Vol. 211, pp. 375-382, Nov. 2020. high work function, and a semiconductor layer, leads emitting greenhouse gases. Moreover, the reduction in Abdelhalim Zekry is a professor of natural fossil fuel resources has increased the necessity [9] Xi Liu, Boming Xie, Chunhui Duan, Zhaojing Wang, Baobing to formation of a depletion region. The electric field electronics at Faculty of Engineering, for finding new alternatives to the traditional non- Fan, Kai Zhang, Baojun Lin, J. Fallon, M. Colberts, Wei Ma, A. Rene, Ain Shams University, Egypt. He at the depletion region results in separation of photo- J. Janssen, Fei Huang, Yong Cao, A high dielectric constant non- renewable energy sources. Based on the estimates has worked as a staff member at fullerene acceptor for efficient bulk-heterojunction organic solar generated charge carriers and a current flow towards several universities. He has published from U.S. Energy Information Administration (EIA), as cells, J. Mater. Chem., Vol. 6, pp. 395–403, 2018. the terminals of the solar cell. The simple and cost- more than 300 papers. He also has of 2019, about 11% of the United States and 26% of [10] Wang, Pang and Wang, Hui and Jeong, Mingyu and Lee, Sang supervised more than 110 Master’s effective fabrication process for metal-semiconductor the global energy consumption is being supplied by the Myeon and Du, Baocai and Mao, Yuchao and Ye, Fanghao and theses and 40 Doctoral Dissertations. Zhang, Huijun and Li, Donghui and Liu, Dan and Yang, Changduk Schottky solar cells make them suitable for use in renewable sources [2]. Prof. Zekry focuses his research and Wang, Tao, “Dopant-free polymeric hole transport materials large-scale photovoltaic devices, and potentially for programs on the field of microelectronics and electronic for efficient CsPbI2Br perovskite cells with a fill factor exceeding commercial applications. However, the performance 84%”, J. Mater. Chem. C, vol. 8, pp. 8507-8514, 2020. applications including communications and photovoltaics. He has been awarded several prizes for his outstanding of these devices can be degraded due to a high [11] Kan, Bin and Zhang, Jiangbin and Liu, Feng and Wan, research and teaching performance. Xiangjian and Li, Chenxi and Ke, Xin and Wang, Yunchuang and leakage current and shunt conductance across the Feng, Huanran and Zhang, Yamin and Long, Guankui and Friend, Walaa Abdelaziz is a teaching metal-semiconductor, which notably reduces their Richard H. and Bakulin, Artem A. and Chen, Yongsheng, “Fine- Tuning the Energy Levels of a Nonfullerene Small-Molecule assistant at the Modern Academy, built-in voltage and ultimately their efficiency in Acceptor to Achieve a High Short-Circuit Current and a Power Egypt. She graduated from Ain comparison to traditional p-n junction solar cells. Conversion Efficiency over 12\% in Organic Solar Cells”, Advanced Shames University in 2005 and Materials, Vol. 30, PP. 1704904, Dec. 2017. earned her Master’s degree in 2012 The remainder of this paper presents the recent from Cairo University. She focuses [12] Lee, E.J.; Choi, M.H., Moon, D.K., “Enhanced Photovoltaic advances in improving the performance of Schottky Properties of Bulk Heterojunction Organic Photovoltaic Devices by her research on renewable energy, junction solar cells are reviewed. an Addition of a Low Band Gap Conjugated Polymer”, Materials, especially solar cells. Figure 1. Efforts needed by different international entities to reduce the total Vol. 9, PP. 996, Nov. 2016. greenhouse gas (GHG) emission in the next decade, in order to limit the rise of global temperature below 2ºC [1].

THE BRIDGE HKN.ORG 27 Feature Feature Modeling organic semiconductor metallic contact and optoelectronic parameters with reference to inorganic semiconductors

THE BRIDGE HKN.ORG 27 Feature Feature A Review of Schottky Junction Solar Cells A Review of Schottky Junction Solar Cells

Solar energy sources occupy about 6% of the total inverted structure, encapsulation using an energy from renewable sources. The availability, insulating material, and other optimized processing accessibility, and low price of solar energy as compared steps, which will be discussed accordingly in the to other renewables has to led to increasing demand. subsequent sections. The use of solar energy is growing across the globe, in both small-scale research and development III. Schottky Junction Solar Cells applications and large-scale manufacturing processes. Multi-junction solar cells with sub-cells made of Examples of successful use of solar energy include Figure 2. (a) Shockley-Queisser detailed balance limit and maximum semiconductors with different bandgap energies, are the Tesla solar roof, portable solar chargers, and off- theoretical Power Conversion Efficiency (PCE) in a simple p-n junction solar usually based on p-n junction. In this structure, the cell, (b) breakdown of other loss mechanisms contributing to lowered PCE [4]. Figure 3. Achieved practical efficiency of solar cells with different grid solar-powered manned and unmanned vehicles. semiconductor materials and structures. The red dashed line represents potential difference between Fermi levels of ann- and Solar energy has proven to be an effective means of the average PCE of Silicon solar cells [5]. p-type semiconductor leads to creation of an electric supplying electricity to remote and developing areas During the last two decades, there have been field and built-in voltage at the junction interface. First Solar Inc. announced in 2014 to have built CdTe- underserved by traditional power grids. numerous efforts in order to reduce the electrical, Photo-generated carriers are then separated by the based solar cells with record high PCE of 21% certified optical, and thermal losses in the solar cells, with the electric field and extracted from the depletion region, for industrial and large-scale fabrication [8]. However, II. Current State of Solar Cells aim of increasing their power conversion efficiency. leading to flow of the current. In a multi-junction due to the environmental concerns because of Increased use of solar energy to meet the world’s Silicon solar cells are dominating the solar energy structure, each sub-cell is basically a single p-n junction, potential toxicity of Cd, and also the usage of rare-earth energy demands has led to large investments and market mainly due to two reasons: 1) the maturity where photons with the energy near to the band edge element such as tellurium, CdTe may face difficulties research in this area during the last few decades. of the technology for the development of Silicon of the semiconductor are absorbed. and limitations in large-scale fabrication over a long However, the greatest two challenges have been solar cells, and 2) availability and abundancy of the semiconductor materials, resulting in lower production period of time [9]. However, there are several theoretical and practical to (1) increase the power conversion efficiency limitations in the design and fabrication of multi- (PCE) of the solar cells, while (2) reducing their cost cost for large-scale fabrication of these devices. Moreover, a reliable power conversion efficiency of junction solar cells based on p-n structure in order for large-scale fabrication [3]. In order to increase to achieve high power conversion efficiency. For the maximum power conversion efficiency in solar silicon, had made it a favorable choice for design and fabrication of industry-scale photovoltaic panels. example, the current mismatch between different cells, most research has been on the optimization layers in a multijunction solar cells leads to severe of the solar cell structure and development of new However, due to the relatively low power conversion efficiency (around 25% in practice) of silicon-based degradation in the efficiency of these devices. Also, semiconductor materials that can be used in a solar producing the required doping level, especially p-type cell that can provide a higher efficiency. The level solar cells, it has become necessary to investigate other suitable materials which can replace Silicon with doping, for wide-bandgap semiconductors has often of photon absorption and the solar cell’s power been accompanied with difficulties, such as impurity conversion efficiency is determined depending on the better performance, higher PCE, and possibly similar or lower cost. Figure 3 shows the research completed Figure 4. Experimental setup for electrical characterization of solar cells incorporation and crystal defects formation, all which semiconductor’s bandgap. In 1961, physicists William under standard illumination condition. can act as recombination centers within the material, Shockley and Hans Joachim Queisser calculated the since 1993 done to investigate different materials In recent years, organic or hybrid solar cells, in which and thus negatively impact the photovoltaic response maximum theoretical power conversion efficiency and structures to achieve higher power conversion an organic-based material (usually polymer) is used of the solar cell [11]. of solar cells achievable from a simple p-n junction efficiency higher than 25% achieved for Silicon solar in either one or all light-absorbing active layers of structure [4]. cells [5]. Copper indium gallium selenide (CIGS) Figure 5. Valence and with tunable bandgap energy of 1–1.7 eV is used to the solar cell structure, are being investigated due conduction energy bands As can be seen in Figure 2.a, a maximum theoretical fabricate thin-film flexible solar cells. In [6], CIGS solar to their interesting electrical and optical properties, for some of the wide- PCE of around 32% is calculated for solar cells made bandgap III-V compound cells are fabricated on flexible copper foil and graphene such as transparency, flexibility, lightweight, and more semiconductors. Hole using semiconductor with bandgap energy around 1.1 has been used as hole transport layer, resulting into importantly, easier fabrication process, which enables localization due to deep eV, under typical solar illumination condition of AM1.5, power conversion efficiency of 9.91%. Recently, T. Kato large-scale fabrication of these solar cells. In [10], a valence band leads to equivalent to 100 mW/cm2. It should be noted that difficulty in producing et al. at Solar Frontier Inc. have achieved a record high new polymer donor, called as PBDB-T-SF is used to high p-type conductivity only 32% of solar energy is converted into electrical power conversion efficiency of 22.9% in development fabricate fullerene-free organic solar cells with thickness in these wide-bandgap power and the rest is either not absorbed (below semiconductors. of a 1 cm2 CIGS (Cu(In1-xGax)(Se,S)2) solar cells, in of around 100-200 nm and record high PCE of 12- bandgap photons), thermally wasted due to relaxation which alkali treatment using cesium on the solar cells 13.1%. One of the major disadvantages of organic Figure 5 shows the energy levels of conduction of hot photons with energy higher than the bandgap, has led to a boost in device performance [7]. solar cells is short-lifetime of these devices, mainly and valence bands of some of the wide-bandgap reflected from the top surface of the solar cells, or non- due to deterioration of the organic material which can Cadmium telluride (CdTe) based solar cells are also compound semiconductors. In these semiconductors, radiatively recombined, resulting into huge losses in possibly reduce the rate of photo-generated current. of interest due to their potential lower production cost deep valence band leads to localization of holes with power conversion efficiency of the solar cell, Figure 2.b. There are several solutions in order to address the than silicon-based solar cells, and comparable power high ionization energy. Therefore, they cannot be used short lifetime of organic solar cells, such as using conversion efficiency with that of Silicon-based devices. as free charge carriers in solar cells and contribute to

THE BRIDGE HKN.ORG 29 Feature Feature A Review of Schottky Junction Solar Cells A Review of Schottky Junction Solar Cells

photo-generated current [12]. This leads to difficulties Narrower depletion region in Schottky junction solar approach, the electric field that is generated by the REFERENCES in producing highly efficientp + or n+ doped layers to cells leads to lower Schottky barrier height and higher fixed negative charges, existing at the interface of the [1] J. Rogelj, M. den Elzen, N. Hihne, T. Fransen, H. Fekete, H. be used as active, tunneling, or metallization contact dark reverse leakage current, mainly due to thermionic- passivation layer and the n-GaAs semiconductor layer, Winkler, R. Schaeffer, F. Sha, K. Riahi, and M. Meinshausen, “Paris Agreement Climate Proposal Need a Boost to Keep Warming junctions in solar cells. field-emission (TFE) which results in a deterioration of keeps the free charge carriers away from the surface Below 2 °C” Nature, 534, 631-639 (2016). In Schottky junction solar cells, an interface between the photovoltaic characteristics. This typically reduces of the semiconductor where they can be trapped and [2] U.S energy Information Administration, Monthly Energy Review, a thin conducting film and a semiconductor, provides the efficiency of Schottky junction solar cells compared non-radiatively recombined. [Online] (2019). the necessary depletion region (band bending) for to p-n junction solar cells. Therefore, a trade-off exists [3] M. A. Green, “Enhancement of Schotty Solar Cell Efficiency between the choosing the suitable material and the Figure 8. Current-voltage Above its Semiempirical limit”, Appl. Phys. Lett., 27, 287-288 separation of photo-generated electron-hole pairs, characteristics of metal/n- (1975). structure of the solar cell in order to achieve the GaAs Schottky junction solar which leads to generation of photo-current. Figure [4] W. Shockley, “The Shockley-Queisser Limit”, J. Appl. Phys., 32, optimized photovoltaic response in the Schottky cells without and with Al2O3 6 shows the difference of operation between a passivation layer. Inset shows 510-519 (1961). solar cells. conventional p-n junction and a Schottky junction the zoomed-in current- [5] Fraunhofer Institute for Solar Energy Systems, Photovoltaic voltage characteristics in the Report. [Online] (2020). solar cell. An abrupt potential barrier is created at the The concept of Schottky junction solar cells have been forward voltage region [18]. interface of this junction due to: 1) difference in the widely used to design and fabricate high efficiency [6] J. K. Sim, S. Kang, R. Nandi, J. Y. Jo, K. U. Jeong, and C. R. Lee, energy levels between Fermi level of the metal and solar cells. For example, researchers have fabricated “Implementation of Graphene as Hole Transport Electrode in Flexible CIGS Solar Cells Fabricated on Cu Foil”, Solar Energy, 162, conduction band of the semiconductor instead of the Schottky solar cells by deposition of 80 nm Indium 357-363 (2018). transitional energy barrier observed at the interface of a Tin Oxide (ITO) on n-GaAs substrate [14]. However, a Ultrathin films of Al2O3 were grown using atomic [7] T. Kato, J. L. Wu, Y. Hirai, H. Sugimoto, and V. Bermudez, p-n junction, and 2) pinning of the edge of Fermi level large dark reverse leakage current density (~10-2 mA/ layer deposition and used as the passivation layer “Record Efficienct for Thin-Film Polycrystalline Solar Cells Up to specific energy levels. cm2), mainly caused by (1) thermionic emission at the in this structure. Figure 8 shows the current-voltage to 22.9% Achieved by Cs-Treated Cu(In,Ge)(Se,S)2”, IEEE J. Photovolt., 9, 325-330 (2019). Schottky barrier, (2) higher carrier recombination rate characteristics of the metal/n-GaAs Schottky junction [8] First Solar, “First Solar Builds the Higher Efficiency Thin Film PV due to crystal defects at the interface, and (3) Schottky solar cells without and with the Al2O3 passivation. A Cell on Record” [Online], 2014, Accessed June 30 2019. barrier height inhomogeneity, limits the efficiency of notable reduction in the leakage current in the reverse [9] V. M. Fthenakis, “Life Cylce Impact Analysis of Cadmium in these solar cells to less than 1%. voltage region, in addition to an increase in the open- CdTe PV Production”, Renew. Sustain. Energy Rev., 8, 303-334 (2004). Figure 7. Schematic circuit voltage is observed for the passivated solar cell. structure of Schottky The proposed strategy shows the effectiveness of the [10] W. Zhao, S. Li, H. Yao, S. Zhang, Y. Zhang, B. Yang, and J. Hou, graphene/n-Silicon passivation layer to improve both the diode-like and “Molecular Optimization Enables Over 13% Efficiency in Organic Schottky solar cells Solar Cells”, J. Am. Chem. Soc., 139, 7148-7151 (2017). photovoltaic properties of the Schottky solar cells [18]. with 2nm ALD-grown [11] Chris G. Van de Walle and J. Neugebauer, “Defect, Impurities Figure 6. Band structure of a typical (a) p-n junction, and (b) metal- passivation layer [17]. and Doping Levels in Wide-Band-Gap Semiconductors”, Brazil. J. semiconductor Schottky junction solar cell at zero bias voltage. IV. SUMMARY AND CONCLUSIONS Phys., 26, 163-168 (1996). The use of Schottky junction solar cells can eliminate Recent advances in design and fabrication of high [12] J. L. Lyons, A. Janotti, and C. G. Van de Walle, “Effects of Hole efficiency solar cells have focused on semiconductor Localization on Limiting p-type Conductivity in Oxide and Nitride the need for the use of highly doped p-type Semiconductors”, J. Appl. Phys., 115, 012014 (2014). materials beyond silicon, and structures beyond p-n semiconductor, and therefore potentially improve [13] D. Pulfrey, “MIS Solar Cells: A Review”, IEEE Trans. Electron. the photovoltaic response of the solar cell. Moreover, The dark reverse leakage current at Schottky junctions junction. Schottky junction solar cells, which are based Dev., 25, 1308-1317 (1978). on the interface of a thin conducting film with a high manufacturing Schottky solar cells may prove to be can be lowered by using passivation layer, which can [14] H. S. Kim et al., “Indium-Tin-Oxide/GaAs Schottky Barrier work function and a semiconductor layer, are receiving cost-effective and industry scalable, since fewer and reduce the recombination of charge carriers [15]. Al2O3 Solar Cells with Embedded InAs Quantum Dots”, Thin Sol. Films, 604, 81-84 (2016). simpler processing steps are required that result into with thickness of 5 nm has been used at Au/Ti/n- much attention due to their ability to produce a lower total production cost [13]. GaAs Schottky junctions and has reduced the leakage reasonable power conversion efficiency. Additionally, [15] H. He et al., “13.7% Efficiency Graphene-Gallium Arsenide Schottky Junction Solar Cells with a P3HT Hole Transport Layer”, -8 -14 2 a simple and cost-effective fabrication process, makes current density from 7.3×10 to 1.2×10 mA/cm Nano Energy, 16, 91-98 (2015). The depletion region for a p-n and Schottky structure the Schottky junction solar cells suitable for use in and increased the Schottky barrier height from 0.77 eV [16] A. Turut et al., “Capacitance-Conduction-Current-Voltage can be calculated using: large-scale photovoltaic devices. However, a narrower to 1.18 eV [16]. Similarly, a 2 nm Al2O3 has increased Characteristics of Atomic Layer Deposited Au/Ti/Al2O3/n-GaAs the power conversion efficiency of graphene/n-Silicon depletion region width and higher leakage current, MIS Structures”, Mater. Sci. Semicond. Process., 39, 400-407 (2015). Schottky solar cell from 7.2% to 8.7% [17]. Figure 7 reduces the overall power conversion efficiency of Schottky solar cells compared to p-n junction solar cells. [17] A. Alnuaimi et al., “Interface Engineering of Graphene-Silicon shows the schematic structure of the Schottky solar Schottky Junction Solar Cells with an Al2O3 Interfacial Layer cell, where the application of Al2O3 passivation layer Recent studies have shown that surface passivation Grown by Atomic Layer Deposition”, RSC Adv., 8, 10593-10597 where WD is the width of the depletion region, ԑs has led to improvement in photovoltaic response. is an effective approach in reducing the density of (2018). is the permittivity of the semiconductor, Na and Nd Ghods et al. have similarly used the concept of field- surface defects at or close to the metal-semiconductor [18] A. Ghods, V. G. Saravade, C. Zhou, and I. T. Ferguson, “Field- are acceptor and donor concentrations, φ is the interface, which eventually, results into improved diode- Effect Passivation of Metal/n-GaAs Schottky Junction Solar Cells effect passivation for reducing the leakage current in Using Atomic Layer Deposited Al2O3/ZnO Ultrathin films”, J. Vac. built-in potential, and Va is the forward or reverse metal/n-GaAs Schottky junction solar cells [18]. In this like and photovoltaic properties of Schottky junction Sci. Technol., 38, 012406 (2020). applied voltage. solar cells.

THE BRIDGE HKN.ORG 31 Feature Feature A Review of Schottky Junction Solar Cells A Review of Schottky Junction Solar Cells

THE BRIDGE HKN.ORG 31 Feature Society Spotlight A Review of Schottky Junction Solar Cells

Dr. Amirhossein Ghods is currently Dr. Ian Ferguson is the Dean a member of technical staff in Park of Southern Polytechnic College IEEE Solid-State Circuits Society: Systems, Inc., working on developing of Engineering and Engineering the next generation of high-resolution Technology at Kennesaw State atomic force microscopy systems. University. Prior to joining Kennesaw, Shaping the IC and Electronics World He received his PhD degree in he had leadership positions in electrical engineering from Missouri both academia (Imperial College, By Abira Altvater, Technical Community Program Specialist and Adam Greenberg, Society Executive Director University of Science and Technology Northwestern University, Georgia in May 2020. His research expertise Tech, UNC Charlotte, Missouri The IEEE Solid-State Circuits Society (SSCS) focuses Get Connected is in design, fabrication, and characterization of novel S&T, etc.) and industry (GEC, EMCORE, etc.). His research on the design, implementation, and application SSCS has a very active Women in Circuits Committee optoelectronic devices, including solar cells and light-emitting expertise is in building interdisciplinary teams to use of solid-state integrated circuits. With over 10,000 diodes, and has resulted in over 30 peer-reviewed journal compound semiconductor materials and devices for that helps enhance professional opportunities at publications, conference proceedings, and book chapters. applications in the areas of sensors, illumination, energy members all around the world, SSCS’ vision networking events at SSCS-sponsored conferences, He was also working as a research intern at Facebook AR/VR harvesting, and spintronics. As an international educator is to foster innovation and excellence in solid- by holding events at local SSCS chapters, and by during summer 2019. His research was mostly focused on and researcher, he has had active collaborations in the US, state circuits for the benefit of humanity through offering leadership activities. characterization of leakage current in blue GaN light-emitting Europe, and Asia, which has resulted in over 550 refereed education, communication, recognition, leadership diodes. journal publications, conference proceedings, books, book opportunities, and networking. To get involved on the grassroots level, members can chapters, and patents. He is Fellow of the Royal Society of join their local SSCS chapters, a vital component of Dr. Chuanle Zhou is currently Arts, Manufactures and Commerce (FRSA), the Institute of Stay Current the Society that provides opportunities to participate assistant research professor at Electrical and Electronic Engineering (IEEE), the Institute of Missouri University of Science and Physics (IOP), the Optical Society of America (OSA) and the SSCS offers many member benefits. Educational in local activities in your area. The Society has over Technology (Missouri S&T). Her International Society for Optical Engineering (SPIE). offerings include online short courses, lectures, and 120 chapters worldwide. research expertise is in characterizing tutorials on the Society’s Resource Center; live and compound semiconductor electrical, 1Electrical and Computer Engineering, Missouri University of Science and Invest in Your Career on-demand webinars; and a distinguished lecturer thermoelectrical, optical and Technology, Rolla, MO 65409, USA SSCS members receive favorable rates on five magnet properties and using these 2 program. SSCS membership includes a subscription Southern Polytechnic College of Engineering & Engineering Technology, sponsored international conferences, at which materials to fabricate devices for Kennesaw State University, Marietta, GA 30060, USA to a portfolio of leading publications, including the applications in the areas of sensors, illumination, energy IEEE Journal of Solid-State Circuits, one of the most attendees participate in educational and harvesting, and spintronics. She has given presentations downloaded scholarly publications of the IEEE. networking sessions. and invited talks in conferences of various areas, including American Physical Society (APS) March Meeting, International SSCS recently launched a technical committee called Conference on Thermoelectrics (ICT), SPIE conference, IEEE Solid-State Circuits Directions (SSCD). Its charter is to Photovoltaic Specialists Conference (PVSC), etc. She has promote forward-looking topics, improve connection had active collaboration with research groups from Purdue, to developments at higher abstraction levels, and Northwestern University and UNC Charlotte. Her research stimulate interactions with other communities. One resulted in over 40 publications, conference proceedings, books, book chapters, and patents. of SSCD’s main activities is holding member-driven technical workshops. Two events have been held recently, including a workshop on democratizing IC IEEE-HKN Member Benefit design, and one on Hardware Security.

The annual SSCS Soccer and Circuits Collaboration and Education Solid-state circuits are the heartbeat of technological Retreat (SOCCER) brings together students from Oregon State University innovation, from the way we entertain ourselves IEEE-HKN’s Premier Event That Connects You With Industry Experts and Stanford University. to the way we deal with global crises such as the Get ready to hear from the experts on how to plan and manage your career, how to stand out as you search for Offerings for Students and Young Professionals COVID-19 pandemic. Join us and help make a job, and what’s next in tech. Watch or rewatch one, two or all of the free webinars now available on demand. The Society also has many benefits for students a difference. • How to Stand Out and Own Your • 12 Key Insights to • Acing the interview! and young professionals, including Predoctoral Career Search in a Virtual World! Career Management • How to Land a Dreamy Achievement Awards, Student Travel Grants, and Enjoy 20% off SSCS membership by entering code • Impacts and Opportunities for a • Succeed as an Entrepreneur Enterprise Computing Job Design Contests. In our ever-changing virtual world, SSC20DCEJAM at checkout. This offer is valid until 1 July 2021 and for first time SSCS members. Better Tomorrow • What They Didn’t Teach You • Start-Ups and Creative Applications SSCS now offers mentoring via an interactive online in Engineering School of Technological Skills platform, allowing young professionals to connect and network with luminaries in the field. Students Sessions Are Free and On Demand Watch On Demand can showcase their creativity by entering the Society’s T-shirt design contests and video contests.

THE BRIDGE HKN.ORG 33 Feature Society Spotlight A Review of Schottky Junction Solar Cells

THE BRIDGE HKN.ORG 33 Partner Spotlight Partner Spotlight

TAP. CONNECT. A student who took one of the hands-on workshops displays the console he built. NETWORK. The initial workshop series provided comprehensive embedded systems knowledge as explained through cloud-based tools, lecture SHARE. Texas Instruments’ Mark Easley Jr. slides and a hands-on demo of a relatable subject – gaming. Connect to IEEE– shows off the two products students no matter where you built as part of hands-on workshops. Hundreds of students participated to build and demo their own are–with the IEEE App. handheld gaming system while gaining appreciation for advanced skills around the Internet of Things (IoT) and specific real-time operating Stay up-to-date systems necessary for engineers. with the latest news Texas Instruments and IEEE-HKN Workshops Following the success of the workshops held in the third quarter of Schedule, manage, 2020, TI expanded the workshop into February and March of 2021 to or join meetups virtually Engage with Remote Engineering Students include content focused on robotics and automation. Get geo and By Mark Easley Jr., University Program Marketing Manager, Texas Instruments Seeking to challenge students with strong technical concepts interest-based relevant for entry into industry, while keeping to a compressed virtual recommendations Texas Instruments (TI) has a long tradition of schedule, company organizers took learnings from the initial IEEE-HKN The world changed in the first months of Read and download student engagement through live workshops and 2020 as news of the global COVID-19 workshops and applied better tactics to engage students throughout your IEEE magazines technology lectures. This specialized engagement is the duration of each session. pandemic spread to all corners of the world. a key facet to the TI University Program, contributing Create a personalized Incorporating more of a social environment with participant experience Fear and uncertainty rocked all aspects to stronger engineering student experiences that introductions, video transitions and ice-breaker activities, students benefit customers when students enter industry, Locate IEEE members of life. Fundamental questions of how realized the workshops covered material and perspectives they often by location, interests, as well as future TI employees. will everyone go to work or school safely, can’t get in the classroom. and affiliations Through a partnership with IEEE-HKN, TI worked what equipment and provisions would be Proven as a successful model for both the participants and TI, the quickly to establish opportunities for students who partnership with IEEE-HKN plans to offer more virtual workshop required to endure the global crisis were were affected across the board with how and where sessions in the future. The workshops will include additional technical being asked, but answers were not easy to they study. The collaboration centered around the topics related to trends facing the industry around IoT, artificial delivery of virtual workshops, and took advantage of find. These challenges in industry required intelligence, machine learning and power electronics. Additionally, a variety of logistics that would enable personalized rapid change to remote work to keep organizers are considering the format to deliver these technical technical content at any location the student resides. operations running, but also to maintain the workshops as fully virtual, hybrid and live in-person events. Delivering the workshop with electronics hardware foundations and systems for future growth and collaboration technology is one thing, but when the crisis is overcome. developing engaging content that would interest students in a remote context is another difficult task.

THE BRIDGE HKN.ORG 35 Partner Spotlight Partner Spotlight

THE BRIDGE HKN.ORG 35 Student Profile Student Profile

What has it meant to you to be inducted or conflated it with the feeling of success in general. back to it later.” He was a very accomplished musical into IEEE-HKN? I didn’t realize until later that I did like solving professional, so at first it struck me as odd that he Quite a bit! At UH, many of our engineering student problems, even if that realization felt very nerdy was not constantly pushing through frustration and organization meetings can be large and intimidating, to admit. stress to become successful. but with HKN, it’s much easier to get to know What do you love about engineering? What is the next BIG advance in engineering? people. It’s especially beneficial to be around people I love nitpicking a design and fine-tuning it until it If the scientific community can get nuclear fusion who are in the same major, at the same level, and works seamlessly. I also really like looking at things figured out, we could seriously reduce the effects of who have similar personalities to you. I have also that have some kind of intuitive symmetry, or energy generation (especially burning fossil fuels) gained an incredible amount of resourcefulness solutions that are elegant and simple. My favorite on the climate. However, if we want to tackle climate and self-confidence by taking on a leadership role projects are those that require my full imagination and change, there are a variety of political and economic in HKN, and I believe I would be a dramatically usually involve writing some code, such as my FPGA solutions that we could implement immediately. different person today had I shied away from Hannah Schroeder projects. You can tell I’m enjoying a project when I I don’t think we have to wait for a big advance in this position. Epsilon Epsilon have several barely-comprehensible sketches next to engineering to solve this problem. Do you have a best HKN story to share? me, I spend too much time making tiny changes to it, University of Houston What is the most important thing you’ve I have two! I thoroughly enjoyed the 2019 Student or I lose track of time while working on it. learned in school? Hannah Schroeder is a senior in Electrical Engineering Leadership Conference (SLC). At that point, I was After going through four years of engineering, I at the University of Houston. She grew up in the the Vice President of the Chapter, and we were have become more comfortable with being in new suburb of Friendswood, Texas, and has had a lifelong still figuring out what our HKN Chapter should look situations or dealing with new information. When penchant for patterns and computers. When Hannah like. We had our first induction later that semester. you’re a perfectionist with a long history of success originally entered college, she pursued a major in I talked to so many people during the SLC, and in very structured environments, discomfort in new Vocal Performance (i.e. classical singing). Although she got some great ideas and advice about how to run situations is normal, and even expected. Being loved the study of music, she discovered that pursuing an HKN Chapter. We hung out quite a bit with the the President of a Chapter with zero established a career in either music education or performance Kappa Psi Chapter from UCSD -- special thanks to structure definitely forced me to put my anxiety aside was unappealing. She decided to change her major them! My other favorite event is Epsilon Epsilon’s first and forge into unfamiliar territory, using my intuition after two semesters. Since then, Hannah has found real event: a tutoring and study session for Circuits 1 and guidance from others. I even discovered a more peace and success in an analytical field. and 2 students that took place in February 2020. We great deal of freedom in the ability to write the Although it was not her initiative to restart the Epsilon had roughly 25 members at the time, all inducted in rules yourself. Since then, I’ve gotten a lot better at Epsilon Chapter of IEEE-HKN, which had been inactive December 2019, and about half of them showed up Hannah Schroeder takes a selfie with fellow Epsilon Epsilon researching topics outside of class, picking up new for roughly 10 years, Hannah was the first Chapter to volunteer at our first event. It warmed my heart so Chapter members. hobbies, and pushing myself outside my President to direct the planning of any Chapter much to see that much enthusiasm, especially when What is your dream job? comfort zone. events, establish regular meetings between officers, we were such a young chapter. I’m hesitant to pick a definitive or narrow field and set up several long-lasting Chapter practices What advice would you give to other and documents to support future members. The Why did you choose to study the right now. I tried that with music. At the moment, I engineering field? love learning about computer hardware, especially students entering college and considering Epsilon Epsilon Chapter has grown rapidly since its studying your major? I grew up around engineers, so engineering always processors, and I know I would find success in a inception. Its first new members were inducted in Say yes to things as often as you can, even if they seemed like a viable career path for someone who fast-moving industry. My dream job is one that is December 2019, and by October 2020, the Chapter are intimidating! My Physics 1 professor asked me was, and is, a big nerd. However, I wanted to pursue exciting enough to keep me learning new things, but was hosting an event roughly every two weeks. The to do research with him my freshman year, and I a career that I loved emotionally, so I initially chose comfortable enough so that I can have confidence in Chapter is now reaching out to students outside of said no because it wasn’t my field. I still regret that. I to study music in college. I eventually realized, my own work. the Engineering college in Engineering Technology was a freshman in Physics 1, nothing was “my field!” though, that I missed the more analytical thinking of and Computer Science, and aims to establish a well- Whom do you admire and why? Also, take the time to get involved! It will take effort one of the STEM disciplines, and that I could still love known, welcoming, and exciting presence on the UH I once told one of my high school music teachers and may be uncomfortable, but you will pick up a music without tying it to my personal finances. That’s campus. In addition to her work with HKN, Hannah that I had been very frustrated with a passage of lot of second-hand knowledge not taught in class, as not to say I don’t love engineering, I do! I just didn’t is also a National Merit Scholar and the recipient of music, but had kept practicing it anyway. He gave realize until later that the satisfaction of working on well as make good friends and study buddies. two UH Engineering Alumni Association awards. She me a funny look and said something similar to a problem was an emotion worth exploring. I had also is an active writer and actor in the Honors College “Why? If you’re frustrated, put it down and come theater club. often dismissed that satisfaction as pretentiousness

THE BRIDGE HKN.ORG 37 Student Profile Student Profile

THE BRIDGE HKN.ORG 37 History Spotlight

The IEEE-Eta all other duties pertaining to THE BRIDGE, including Kappa Nu Board THE BRIDGE Magazine publicity for the Chapter” (Article II, Section 9, E.). of Governors While this position is no longer required, Chapters are of IEEE-Eta Kappa Nu: encouraged to submit significant Chapter news and cordially invites events for possible publication. In particular, Chapter celebrations of Founders Day are highlighted each year. the members Part II of the 2021 By Steve E. Watkins, Gamma Theta Chapter Graduation Class, Family, & Friends THE BRIDGE magazine was named for the emblem of IEEE-Eta Kappa Nu (HKN) – the Wheatstone to the bridge. Just as this emblem reflects the three ideals for member eligibility, the magazine promotes HKN and its Scholarship, Character, and Attitude values. The content includes an archival record of the global association, highlights of Chapter activities, recognition of technical achievements, historical notes for the profession, and other content of interest to student and professional members.

As a publication of IEEE THE BRIDGE Covers for the Millenium (2000) and Centennial (2004) Issues since 2010, THE BRIDGE has an open-access Covers for key historical issues are shown above. electronic distribution. The Millennium issue (Vol. 96, No. 3. 2000) reprints The current issue and an selected content of THE BRIDGE from 1909 to archive of these electronic 1995. The Centennial issue (Volume 100, No. 1, Saturday, 5 June 2021 issues are available on the 2004) along with the Diamond Jubilee issue (Volume IEEE-HKN website. Anyone 75, No. 2, 1980) preserve a wealth of historical 2 pm (ET) interested in receiving notice information and photographs for the Society. Lists of of just-published issues can HKN leaders, Eminent Members, and award winners The event will include a virtual procession of the make an e-mail request to are included. Scans of these print issues are available members of the Class 2021, the presentation of the THE BRIDGE on the IEEE App [email protected]. THE BRIDGE at the archive on the Engineering and Technology Outstanding Chapter Awards, remarks from the 2020 recently was added to the IEEE app for even easier History Wiki page https://ethw.org/Eta_Kappa_Nu. Outstanding Student Award recipient, and the access via mobile devices. THE BRIDGE accepted advertising starting in 1917 as elevation of Dr. Maxine Savitz, Vice President, National As the official publication of IEEE-HKN, the magazine a connection to industry. Companies such as General Academy of Engineering, to HKN Eminent Member. was and is a primary means of informing both student Electric, Westinghouse, NRC, and Hughes Aircraft More details to come. and alumni members about activities of the Society. were frequent sponsors. Educational connections Board elections, new Chapters, award presentations, have become important recently, with universities REGISTER HERE and conferences are examples. It also serves to note promoting their graduate programs. These university significant Chapter activities. Alton B. Zerby, Executive sponsors are also shown on the IEEE-HKN website. Secretary 1934-1958, considered the magazine A major portion of recent issues have included original “a vehicle of communication between students feature articles and a few reprinted articles from IEEE and alumni.” publications. These features are intended to give Chapter submissions were an essential part of the readers insight into technical and professional subjects magazine content. The HKN Constitution from of interest. Each issue has a theme, and several issues 1958 required officer teams to include a Bridge were organized by guest editors. The issue themes https://event.on24.com/wcc/r/3010208/2CA812A5197EA0E891F4DA6FBD2AE403 Correspondent and identified these Chapter officers as and an index of feature articles that have appeared supporting staff to the publication’s editor. The duties in THE BRIDGE for 2013 to 2020 are listed below. for Bridge Correspondent were to “submit reports of Reprint articles are noted. the Chapter’s activities to THE BRIDGE and perform

THE BRIDGE HKN.ORG 39 History Spotlight

THE BRIDGE HKN.ORG 39 History Spotlight History Spotlight

About the Author: Steve E. Watkins was the 2018 Issue 2, Theme: Cybersecurity Issue 2, Theme: Neural Networks President of IEEE-Eta Kappa Nu and is co-Editor- HKN History Note: Interest was sufficient to offer Guest Editor: Egemen K. Cetinkaya. • “Outsmart Moore’s Law with Machine Learning,” Dustin Tanksley in-Chief for THE BRIDGE. He was inducted by the a lifetime subscription plan starting in 1935. • “Cyber-Physical Security Assessment (CyPSA) for Electric Power and Donald C. Wunsch. Gamma Theta Chapter at Missouri University of HKN founders Maurice L. Carr and Edmund B. Wheeler Systems,” Katherine R. Davis, Robin Betthier, Saman A. Zonouz, • Determining Optimum Drop-out Rate for Neural Networks,” were Life Subscribers Number 1 and 2, respectively. Gabe Weaver, Rakesh B. Bobba, Edmund Rogers, Peter W. Sauer, Josian A. Yoder. Science and Technology. He is professor at Missouri and David M. Nicol. • Distributed Stochastic Optimal Flocking Control for Uncertain S&T and has been a Faculty Advisor for the Gamma • “Security Analytics: Essential Data Analytics Knowledge for Networked Multi-Agent Systems,” Hao Xu and Wenxin Liu. Cybersecurity Professionals and Students,” Rakesh Verma, Murat Theta Chapter since 1992. Issue 3, Theme: Bridging Academic Excellence to Lifetime Kantarcioglu, David Marchette, Ernst Leiss, and Thammar Solorio. Excellence: Three Engineers’ Roadmap to Success Index of Feature Articles in THE BRIDGE Magazine of IEEE-HKN since 2013 • “A Brief Review of Security in Emerging Programming Networks,” Guest Editor: Marcus Huggans Volume 109, 2013 Volume 111, 2015 Egemen K. Cetinkaya. • “The Secret of Success,” Jim Watson. Issue 1, Theme: Engineering for Space Applications Issue 1, Theme: Smart Grid and Renewable Energy Issue 3, Theme: Sensors and Sensing • Creating the Builders of Tomorrow,” Shameeka Emanuel. • “123 Million Miles in Space and 12 Miles in LA Traffic,” • “The Big Picture: Smart Research for Large-Scale Integrated • “Terahertz Range Weak Reflection Optical Fiber Structures • My Leadership Journey,” Alan Mingo. Burt Dicht. Smart Grid Solutions,” Mladen Kezunovic, Vijay Vittal, Sakis for Distributed Sensing,” Zhen Chen, Gerald Hefferman, and • The Mission and Engineering Challenges of the James Webb Meliopoulos, and Tim Mount (Reprint). Tao Wei. Volume 115, 2019 Space Telescope,” Jonathan Arenburg. • “Growing the Smarter Workforce,” Peter W. Sauer. • “Mechantronic Design of an Actuated Biomimetric Length and Issue 1, Theme: Making an Impact • “The Universe in a Supercomputer,” Joel R. Primack (Reprint). • “Interconnection of Renewable Energy to the Power Grid,” Sensor,” Kristen N. Jaax and Blake Hannaford. • Can STEAM Education Help Lift Developing Nations?” Kayla Ninh. • “Deflecting Asteroids,” Gregory L. Matloff (Reprint). Vincent J. Forte. • “Unconventional Biosignal Sensing with Passive RFID Tags,” • IEEE-HKN Chapter and Student Branch Work Together to Issue 2, Theme: Engineering Ethics • “Smart Grid – Safe, Secure, Self-Healing,” S. Massoud Amin Shrenik Vora and Timothy P. Kurzweg. Increase Impact on Community,” Dauda Ayanda. • “Creating the IEEE Code of Ethics: The History Behind and Anthony M. Giacomoni (Reprint). • “2018 Annual Report for IEEE-Eta Kappa Nu,” Steve E. Watkins. • “Smart Grid: The Role of the Information Sciences,” Volume 113, 2017 the Process,” Emerson W. Pugh. Issue 2, Theme: Connecting the World with Amateur Radio H. Vincent Poor. Issue 1, Theme: UAVs • “Lessons from the Storm (Hurricane Katrina),” Byron Newberry. Guest Editor: Steve E. Watkins • “Intel: Breaking Ground in the Drone Industry,” Joan Tafoya. • “Professional and Ethical Dilemmas in Software Engineering,” Issue 2, Theme: Autonomous Vehicles • “Amateur Radio and Careers in Electrical and Computer • Safety and Privacy Policy Regarding Unmanned Aerial Vehicles Brian Berenbach and Manfred Broy (Reprint). • “A 13,000km Intercontinental Trip with Driverless Vehicles: The Engineering,” Ward Silver. (UAVs),” Logan T. DiTullio. • “Are There Experts in Engineering Ethics,” VIAC Experiment,” Massimo Bertozzi, Alberto Broggi, Alessandro • “Electrical and Computer Engineering and Amateur Radio,” • “Connectivity in Networked Unmanned Aerial Vehicles,” Rajdeep Karl D. Stephan (Reprint). Coati, and Rean Isabella Fedriga (Reprint). Dennis Silage. Dutta, Zachary Ruble, and Daniel Pack. • “Preparing for High Ethical Standards,” Steve Starrett. • “’Drones’ and the Future of Domestic Aviation,” • “Great Impedance Match for Knowledge Transfer: Amateur • “A Student-Built Fixed-Wing UAS for Simulated Search-and- Issue 3, Theme: Celebrating Engineering Accomplishments John Villasenor (Reprint). Radio as Part of Electrical and Computer Engineering Education,” Rescue Missions,” Chase R. Yasunaga, Kalani R. Danas Rivera, • “Bridges I have Crossed,” Thomas B. Greenslade, Jr. • “Sensors Technologies for Intelligent Vehicles Perception Dennis Derickson, Charles “Chuck” Bland, Jack Gallegos, and Joseph D. Harris III, Marte A. Matinez, Jr., Stephen L J. Mau, • “Bistatic Radar,” Hugh Griffiths. Systems: a Comparison Between Vision and 3D0LIDAR,” Marcel Stieber. Reyn H. Mukai, Kevin Y. Sonoda, Wayne A. Shiroma, and A. • “Designing the First Microprocessor,” Marcian E. Hoff (Reprint). Alberto Broggi, Paolo Grisleri, and Paolo Zani. • “SeaPerch – On the Yellow Brick Road,” Susan Giver Nelson. Zachary Trimble. Issue 3, Theme: Graduate Education • “An Early History of the Internet,” Leonard Kleinrock (Reprint). • “Why should I go to Graduate School,” Karen Panetta. Issue 2, Theme: Rebooting Computing Volume 110, 2014 Issue 3, Theme: Focus on IEEE-HKN • Hear it from Professionals: Lessons Learned and Advice • “From Ethics to Innovation: A Common Code,” John C. Havens. • “Suggestions for Electrical Research in Engineering for Graduate School.” Issue 1, Theme: Lasers, Optics, and Photonics • “The IEEE Rebooting Computing Initiative,” Elie Track Colleges,” V. Karapetoff (Reprint). • Graduate Student Profiles,” Katelyn Brinker, Emily Hernandez, • “Laser Safety for Electrical Engineers,” David Brown. and Alan Kadin. • “A Tale of Two Cities: Biosensor Engineering for Water and Wendy P. Fernandez. • “Quantum Optics for the 21st Century Electrical Engineer,” Management,” Evgeni Eltzov, Adarina Low Yuen Kei, Issue 3, Theme: Outreach and Impact Sean J. Bentley. and Robert S. Marks. • “MOVE Makes a Difference,” James M. Conrad, Gregg Volume 116, 2020 • “Smart Bridges using Fiber Optic Sensors,” • “Special History Section.” Vaughn, Grayson W. Randall, Mary Ellen Randall, and Steve E. Watkins (Reprint). Issue 1, Theme: Members Engaged and Inspired: Percy F. Shadwell, Jr. • “A Brief History of High-Power Semiconductor Lasers,” Volume 112, 2016 2019 in Review • “Project Lead the Way: A STEM Program for Electrical and David F. Welch (Reprint). • “2019 Year in Review: Members Engaged and Inspired.” Issue 1, Theme: Biologically Inspired Engineering Computer Engineering Students,” R. Joe Stanley, Stuart Baur, and Issue 2, Theme: Engineers’ Involvement in Society Guest Editor: Jacquelyn K. Nagel. Ben Yates. Issue 2, Theme: Beyond Engineering: Atypical Careers and • “Can IEEE Save the World,” Moshe Kam. • “Application of Natural Systems to Engineering at NASA,” • “HKN’s Greatest Asset: Alumni,” Larry Dwon (Reprint). Contributions by Engineers • “Aiding Autism Through Technology,” Sampathkumar Kennie H. Jones, George M. Studor, and Jacquelyn K. Nagel. • “Public Policy: A Different ayW to Change the World,” Veeraraghavan and Karthik Srinivasan. • “Auto-Gopher 2 – a Biologically Inspired Deep Drill for Volume 114, 2018 Russell T. Harrison. • “Intellectual Property: What’s Mine is Mine and • “Wearable Sensors and Systems,” Paolo Bonato (Reprint). Planetary Exploration,” Yoseph Bar-Cohen, Kris Zacny, Mircea Issue 1, Theme: Quantum Entanglement and Engineering What’s Yours is Mine,” Orin E. Laney. • “Influencing Public Policy,” Russell T. Harrison. Badescu, Hyeong Jae Lee, Stewart Sherrit, Xiaoqi Bao, Gale L. Guest Editor: Sean J. Bentley Issue 3, Theme: Spotlight on Student undergraduate Research Paulsen, and Luther Beegle. • “Quantum State Generation in Optical Frequency Combs for Issue 3, Theme: The Future of Renewable Energy: Generation, Guest Editor: Keenan Johnson. • “Leveraging Nature’s Gifts in the Design of Control Systems,” Quantum Computing,” Yanbing Zhang, Piotr Roztocki, Christian Transmission, Consumption • “Utilizing Computational Electromagnetics for the Advancement Mark Kerbel. Reimer, Stefania Sciara, Michael Kues, David J. Moss, and Guest Editor: Roderick Jackson of Photonic Processor Communications,” Jelena Notaros. • “Design of a Bio-inspired Optical Current Transducer,” Jacquelyn Roberto Morandotti. • “The Future of Renewable Energy Generation: Photovoltaic • “New Completion-Tree Topology for Quasi-delay Insensitive K. Nagel and Steve E. Watkins. • Quantum Cryptography and Side Channel Attacks,” Colin Lualdi, Materials,” Annalise Maughan, Kai Zhu, and Joseph J. Berry. Logic,” Anjian Wu and Alain J. Martin. • “Dinosaurs Make Light Work – From the Engineering Problem Stephen Pappas, Daniel Stack, and Brandon Rodenburg. • “The Future of Renewable Energy Transmission: An Autonomous • “Telemetry Processor for a Remotely Operated Vehicle,” to an Innovative Lightweight Product,” • “Quantum Teleportation from Sci-fi to the Quantum Wi-fi,” Energy Grid,” Benjamin Kroposki, Andrey Bernstein, and Jennifer Keenan Johnson. Hans-Joachim Weber and Martin Weber. Daniel Cavalcanti and Paul Skrzypczyk. King. • “GazePointer: Computer Vision Based Eye Gaze Tracking for • “The Future of Renewable Energy Consumption: Grid-Interactive Human-Computer Interaction,” Muhammad Usman Ghani and Efficient Buildings,” Nikitha Radhakrishnan, Erika Gupta, Karma Muhammad Adnan Siddique. Sawyer, and Monica Neukomm. • “Trial by Fire,” Robin R. Murphy (Reprint) Citation: S. E. Watkins. “THE BRIDGE Magazine of Eta Kappa Nu: Part II,” IEEE-HKN THE BRIDGE Magazine, 117(2), 13 May 2021.

THE BRIDGE HKN.ORG 41 History Spotlight History Spotlight

THE BRIDGE HKN.ORG 41 In Memoriam In Memoriam

Innovator in Electronic Displays Former HKN National President

Sourced from the UCLA Samueli School of Engineering Sourced from Tributearchive.com

IEEE Life Member Lawrence E. Tannas Jr., a visionary engineer who pushed John E. Farley, the HKN National President in 1968 and 1969, died on the evolution of the electronic displays industry from its early days in 6 February 2021. He was 95 years old. avionics to a global presence, died 5 February 2021. He was 84. Known to his friends and family as “Jack,” he spent most of his life as a Known as “Larry” to all, Tannas earned a bachelor’s and a master’s degree resident of Park Ridge, Illinois, where he raised his family, and commuted in engineering at UCLA in 1959 and 1961, respectively. to his offices in downtown Chicago. Lawrence E. After graduation, Tannas worked in Southern California’s burgeoning John E. Farley, 95 Born in Chicago in November of 1925 to Miles and Bess Farley, John aerospace industry. He developed automated landing systems at General Tannas Jr., 84 served in the United States Navy during WWII in the Pacific theater. He Alpha Chapter, Electric Co., designed the backup reentry-guidance display for the Apollo earned his bachelor’s degree from the University of Illinois at Urbana- University of Illinois, IEEE Life Member reentry vehicle at Honeywell International Inc., and at Martin Marietta Inc., he created a cockpit for the SV-5 manned space vehicle—an Air Force Champaign and a master’s degree from Northwestern University, both in Urbana-Champaign UCLA Electrical Engineering. prototype that was an important predecessor to NASA’s space shuttle. HKN National President, As Tannas progressed in his career, he began to specialize in technologies John was an engineer and manager for various companies within the 1968-1969 for flat-panel displays, in particular, liquid crystal displays (LCDs). Tannas former AT&T/Bell System, primarily at Illinois Bell Telephone. He also was instrumental in the early growth of this technology and its evolution. helped develop new communications technologies at Bell Labs in It was his work at Rockwell Autonetics in the 1970s that established the New Jersey. world’s first production line for LCDs. He then perfected a manufacturing John was active in promoting electrical engineering and STEM careers process for electroluminescent displays while at Aerojet through his work with Eta Kappa Nu (HKN), the Electrical Engineering Electro-Systems Corp. Honor Society, where he served as national president from 1968 to In 1999, he founded Tannas Electronic Displays, Inc., which specialized in 1969. He also remained active at his alma mater, serving on the Electrical research, development, manufacturing and licensing of intellectual property Engineering Alumni Board at the University of Illinois. He also was a co- for resizing LCDs. In 2015, he sold the company to Pixel Scientific Inc., but founder of a marine instrumentation business. remained active in the industry as president of the consulting firm Tannas Electronics. Throughout his career, he was awarded 28 patents and had His passion was sailing on Lake Michigan. He was an active sailboat racer more than 10 others pending. for over 50 years. He enjoyed encouraging others to become active in the Parallel to his pioneering career, Tannas was also a proponent of elevating sport of sailboat racing. electronic displays, also known as information displays, to be a vibrant He is survived by his wife, Karin (Clafford) Farley, whom he met when they scientific field in its own. He was a fellow and past-president of the Society were both students at the University of Illinois. He also is survived by two for Information Display (SID). children, four grandchildren, and one great-grandchild. From 1980 to 2000, Tannas developed and taught advanced engineering classes on information displays at UCLA Extension, as well as at other institutions. He was also the author of more than 50 technical papers, and wrote and edited the first definitive book on flat-panel displays, “Flat-Panel Displays and CRTs,” published in 1983 by Van Nostrand Reinhold. Tannas is survived by Carol, his wife of 64 years, three children, and 10 grandchildren.

Photo credit: UCLA Samueli School of Engineering Photo credit: tributearchive.com

THE BRIDGE HKN.ORG 43 In Memoriam In Memoriam

Innovator in Electronic Displays Former HKN National President

Sourced from the UCLA Samueli School of Engineering Sourced from Tributearchive.com

Photo credit: UCLA Samueli School of Engineering Photo credit: tributearchive.com

THE BRIDGE HKN.ORG 43 IEEE-EtaIEEE Eta Kappa Kappa NuNu LaunchesLaunches IEEE-HKN IEEE-HKN CareerCareer Center Center

IEEE Eta Kappa Nu is proud IEEE-Eta Kappa Nu is proud to announce its new IEEE- to announce its new IEEE-HKN HKN Career Center - the Career Center–the premier premier resource to connect resource to connect career career opportunities with opportunities with highly highly qualified Engineering qualified engineering talent. talent. LOG ON TODAY! IEEE-HKNIEEE-HKN Career Career Center Center LOG ON TODAY! will allowwill youallow youto: to: Manage Your Career: MANAGE YOUR CAREER: • Search and• apply Search to moreand apply Engineering to more Engineering jobs than jobsin any than other in any job other bank. job bank. • Upload your• anonymous Upload your anonymousresume and resume allow and employers allow employers to contact to contact you through you through IEEE-HKN IEEE-HKN CareerCareer Center’sCenter’s messaging messaging system. system. • Set up Job •Alerts Set upspecifying Job Alerts your specifying skills, interests,your skills, andinterests, preferred and preferred location(s) location(s) to receive email to receive email notifications notifications when whena job isa jobposted is thatposted matches that yourmatches criteria. your criteria. • Access career• Accessresources career and resources job searching and job tips searching and tools. tips and tools. • Have your •resume Have yourcritiqued resume by critiqued a resume-writing by a resume-writing expert. expert. RECRUIT FOR OPEN POSITIONS: Recruit for Open Positions: • Post your job in front of the most qualified group of Engineering talent in the industry. • Post your job in front of the most qualified group of Engineering talent in the industry. • Promote your jobs directly to candidates via the exclusive Job Flash email. • Search the •anonymous Promote your resume jobs directly database to candidates to find viaqualified the exclusive candidates. Job Flash email. • Manage your• posted Search thejobs anonymous and applicant resume activity database easily to findon thisqualified user-friendly candidates. site. • Manage your posted jobs and applicant activity easily on this user-friendly site.

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