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Investigation of Dna Nucleobases for Bio-Organic Light Emitting Diodes

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Investigation of Dna Nucleobases for Bio-Organic Light Emitting Diodes INVESTIGATION OF DNA NUCLEOBASES FOR BIO-ORGANIC LIGHT EMITTING DIODES A DISSERTATION THESIS SUBMITTED TO THE GRADUATE FACULTY OF THE UNIVERSITY OF CINCINNATI IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE OF DOCTOR OF PHILOSOPHY (PH.D.) OF ELECTRICAL ENGINEERING ELIOT FRENCH GOMEZ UNIVERSITY OF CINCINNATI DEPARTMENT OF ELECTRICAL AND COMPUTING SYSTEMS COMMITTEE CHAIR: ANDREW J. STECKL, PH.D. SUBMITTED ON JANUARY 13TH, 2015 ABSTRACT Natural electronics is the field that incorporates biological molecules in organic electronic devices to create inexpensive, renewable, performance-enhancing, and environmentally safe alternatives for the electronics industry. Natural DNA, for example, has been incorporated as an electron blocking layer (EBL) to improve device efficiency and luminance in organic light emitting diodes (OLED). OLEDs require a diverse set of materials with optical and electrical properties that meet the rigorous design requirements of the device. DNA, being one of the few materials in OLEDs, lays the groundwork for other natural material to be explored. The nucleic acid bases from the DNA and the RNA (adenine, guanine, cytosine, thymine, uracil) are excellent options for the next steps in natural OLED electronics. The bases form thin films directly by thermal evaporation, unlike DNA that requires a surfactant and solution processing. The bases were shown to have a wide range of opto/electronic properties such as refractive index, dielectric constant, resistivity, and electron/hole transport making them a good candidate for OLEDs. The thin film properties and performance of the bases were explored by depositing the individual bases as the EBL and hole blocking layer (HBL) in place of conventional OLED material. It was shown that adenine and guanine performed well as EBLs, exceeding the efficiency of the baseline device (52 vs 39 cd/A), which contained non-biological material. It was also demonstrated that OLEDs with very high efficiency can be obtained using a thin layer of thymine as an EBL, resulting in a peak efficiency of 76 cd/A and a higher maximum luminance (132,000 cd/m2) than the baseline OLED (100,000 cd/m2). In the hole blocking layer, uracil performed well by transporting electrons and blocking hole transport to provide the highest emission efficiency of the bases. The final set of experiments demonstrated that adenine increased the hole injection of gold electrodes due to the natural affinity the base has with gold, corresponding to a 4-7× increase in luminance. Thin film gold is an attractive electrode alternative for OLEDs on plant-based cellulose substrates since it does not require high temperature annealing and has high conductivity. Gold cannot be directly evaporated on the rough cellulose substrate, therefore, a template stripping i procedure was employed using epoxy to lift off the gold electrode from Si wafers, in combination with adenine as a hole injector to yield high quality and efficient OLEDs. Nucleic acid bases are a diverse set materials that result in performance-enhancing, inexpensive, and natural-based OLEDs. ii iii ACKNOWLEDGEMENTS Good work is only accomplished with the support of great people, and there are many I am indebted to over the course of my graduate studies. I would like to thank my academic advisor, Dr. Andrew Steckl who has been incredibly supportive guiding me up and down every mountain of this journey with persistence, diligence, and the best intentions to see me succeed. Dr. James Grote whose financial support and knowledgeable direction made this project possible. I would like to thank my dissertation committee who have, not only provided feedback and discussion on my work, but have been inspirational professors throughout my academic career at UC. At the Nanoelectronics Laboratory, I am grateful to my colleagues past and present, especially former student, Dr. Hans Spaeth, who raised me up from a young graduate student to where I am today. Other colleagues, Vishak Venkatraman, Dr. Han You, Adam Zocco, and Sumit Purandare who have provided good discussion, aided in experiments, and were good friends during my time in the lab. I would also like to thank Dr. Necati Keval in Chemistry whose friendship and help over the years has been most appreciated. I would like to express my deepest gratitude and love for my wife, Melanie, who has sacrificed so much over these past years to get where I am now. She has truly been the solid foundation behind this work and has been my greatest support. I would like to thank my parents, Elias and Sarah, who have supported me unwaveringly both financially and in spirit on my academic endeavors: my father who inspired in me a firm work ethic and love for engineering, my mother who helped so much caring for the twins while we worked and has been very supportive, along with Ciss and Michael Beatty. My brother, Andre Gomez, whose artistic eye has complemented my engineering brain. Finally, I would like to acknowledge the deep friendships we have formed over the years in Cincinnati, especially the Church of Missio Dei. They have walked, encouraged, prayed, and celebrated with us through every trial and experience we have been through, and they have helped me understand how to do all work done in light of the gospel of Jesus Christ. Soli Deo Gloria. iv “Call to Me and I will answer you and tell you great and unsearchable things you do not know” Jeremiah 33:3 v MEMBERS OF THE DISSERTATION COMMITTEE Dr. Andrew J. Steckl (Advisor & Committee Chair) School of Electronics & Computing Systems Nanoelectronics Laboratory University of Cincinnati Cincinnati, Ohio Dr. James G. Grote (Co-Advisor) Air Force Research Laboratory Materials and Manufacturing Directorate Wright-Patterson Air Force Base Dayton, Ohio Dr. Fred R. Beyette, Jr School of Electronics & Computing Systems Point-of-Care - Center for Emerging Neurotechnologies University of Cincinnati Cincinnati, Ohio Dr. Peter B. Kosel School of Electronics & Computing Systems GaAs Devices and ICS Lab University of Cincinnati Cincinnati, Ohio Dr. Ian Papautsky School of Electronics & Computing Systems Bio Micro Systems Lab University of Cincinnati Cincinnati, Ohio vi TABLE OF CONTENTS LIST OF FIGURES ................................................................................................................................ ix LIST OF TABLES ............................................................................................................................... xiv COMMON ABBREVIATION & SYMBOLS ............................................................................................ xv Chapter 1. Introduction to Natural Electronics .......................................................................... 1 1.1. Natural Electronics ................................................................................................................ 2 1.2. OLEDs to Bio-OLEDs .......................................................................................................... 6 1.3. Nucleobases and motivation .................................................................................................. 8 1.4. Summary and Thesis Outline .............................................................................................. 11 Chapter 2. OLEDs and Experimental Methods ........................................................................ 12 2.1. Overview of OLEDs ............................................................................................................ 12 2.2. General OLED Fabrication and Characterization Procedures .............................................. 17 2.2.1. OLED Fabrication ...................................................................................................................................17 2.2.2. OLED Characterization ........................................................................................................................19 2.3. Summary ............................................................................................................................. 21 Chapter 3. Nucleobases and Thin Film Properties .................................................................... 23 3.1. Nucleobase Origin and Synthesis ........................................................................................ 23 3.2. Thin Film Properties ............................................................................................................ 25 3.2.1. Thermogravimetric analysis ..............................................................................................................25 3.2.2. AFM and SEM ............................................................................................................................................28 3.3. Optical and Electrical Properties ......................................................................................... 30 3.3.1. Optical Spectroscopy .............................................................................................................................30 3.3.2. Ellipsometery ............................................................................................................................................31 3.3.3. Dielectric constant..................................................................................................................................32 3.3.4. HOMO/LUMO levels ...............................................................................................................................33 3.4. Summary
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