DOCSLIB.ORG

Organic Semiconductors for Device Applications: Current Trends and Future Prospects

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Organic Semiconductors for Device Applications: Current Trends and Future Prospects DOI 10.1515/polyeng-2013-0267 J Polym Eng 2014; 34(4): 279–338 Review Shamim Ahmad* Organic semiconductors for device applications: current trends and future prospects Abstract: With the rich experience of developing silicon 1 Introduction devices over a period of the last six decades, it is easy to assess the suitability of a new material for device appli- A wide range of organic semiconductors (OS) are cur- cations by examining charge carrier injection, transport, rently being explored extensively for their applications and extraction across a practically realizable architecture; in organic electronics (OE) primarily due to the growing surface passivation; and packaging and reliability issues need of substituting silicon (Si) with some alternative besides the feasibility of preparing mechanically robust cost-effective materials offering relatively simpler and wafer/substrate of single-crystal or polycrystalline/ commercially viable technologies [1–7] at least in some amorphous thin films. For material preparation, param- niche areas. Based on the recent developments in the area eters such as purification of constituent materials, crystal of OS, processes involving printing of semiconductor, con- growth, and thin-film deposition with minimum defects/ ductor, and dielectric patterns on a variety of hard as well disorders are equally important. Further, it is relevant to as flexible substrates are fast emerging as part of a com- know whether conventional semiconductor processes, mercially viable technology for the upcoming OE devices. already known, would be useable directly or would require In contrast to OS (primarily Si), the additional possibility completely new technologies. Having found a likely can- of chemically modifying the organic molecules by incor- didate after such a screening, it would be necessary to porating a number of functional groups during synthesis identify a specific area of application against an existing resulting in a number of chemical functionalities along list of materials available with special reference to cost with significant influence on the charge carrier transport reduction considerations in large-scale production. Vari- properties [8] is adding further impetus to make this kind ous families of organic semiconductors are reviewed here, of search more attractive and meaningful. The examples, especially with the objective of using them in niche areas cited later, highlight this concept further. For instance, it of large-area electronic displays, flexible organic electron- is now easy to design a molecule to have the desired fea- ics, and organic photovoltaic solar cells. While doing so, tures in terms of its solubility in a specific solvent, color it appears feasible to improve mobility and stability by of the light emission and a typical crystalline molecular adjusting π-conjugation and modifying the energy band- packing, to name a few. Some such features realized from gap. Higher conductivity nanocomposites, formed by modifying the molecular designs have already been put to blending with chemically conjugated C-allotropes and use in a number of newer applications as mentioned here. metal nanoparticles, open exciting methods of design- A good example is that of nonvolatile memory elements ing flexible contact/interconnects for organic and flexible [9], wherein polyvinylidene fluoride copolymers and tri/ electronics as can be seen from the discussion included tetra-fluoroethylene radicals [10] were used in preparing here. useful devices that were found especially appropriate for flexible electronic circuits. In another case, the end groups Keywords: conjugated polymers; crystalline/polycrystal- of an organic sensor array were modified such that they line organic compounds; hopping conduction; organic not only responded to chemical and biological species field-effect transistors; organic semiconductors. but also measured pH levels [11], food freshness, toxic compounds, stress, and pressure in apparels [12]. Rapid *Corresponding author: Shamim Ahmad, Center of Excellence in growth witnessed in OE is offering several newer areas of Nanotechnology, Confederation of Indian Industry Western Region, applications with better performances, improved reliabil- Ahmedabad, Gujarat 380006, India, e-mail: [email protected] ity and stability, long lifetime, good control, and repro- ducibility as demanded by the different industry sectors. For instance, organic light-emitting device (OLED)-based 280 S. Ahmad: Organic semiconductor devices displays, marketed by Philips and Organic Electronic A number of OS-based devices, especially OLEDs Components, in cell phones [13] and other mobile devices [2, 47–49], OPV solar cells [50–59], and organic field-effect along with car radios and digital cameras are some of transistors (OFETs) [1, 60–64], are fastly being developed the applications that are expected to multiply in the near involving conjugated organic molecules that offer special future. features in terms of tunable energy band-gap, redox poten- The quest for exploring the electronic applications of tials, and charge carrier transport properties, besides OS has already grown manifold in recent past [8, 14–23] being easy to process. These materials and processes are while attempting to replace the use of inorganic materials certainly going to offer the lightweight, low-cost, thin- in some relevant areas. In addition, efforts are also being film, large-area, and flexible electronics of tomorrow. made to explore newer concepts and theoretical models including molecular-level designs for controlling the structural, physical, and chemical properties of organic 1.1 Organic molecules for device applications molecules to meet the system requirements better in the future. This kind of approach is currently more relevant, From the point of view of device applications, the organic as the earlier attempts made in realizing OS devices faced molecules are conveniently classified into groups accord- unavoidable problems of material instabilities during ing to the nature of the charge carrier transport they processing besides the large density of structural defects support, for instance, hole and electron-transporting (HT/ introduced during material growth that prevented the ET) materials, besides their architecture involving small- fuller exploitation of the intrinsic charge carrier transport molecule oligomers or macromolecular polymers and properties. dendrimers. OS are currently getting almost practically poised for Commonly used definition of p- or n-type material supplementing and/or replacing the conventional OS, does not necessarily reflect the intrinsic ability of an especially in some niche areas, because of the associated organic material to transport holes or electrons as men- distinct advantages. From the 1980s onward, OS have gone tioned in the published literature. Rather, it only speci- through various stages of development meant for improv- fies how easily holes and electrons are injected from their ing the material quality that led to and even surpassed the contact electrodes. This subtle deviation from the classic performance of amorphous Si (α-Si) [24] in terms of the definition was further elaborated in subsequent studies charge carrier mobilities in organic thin-film transistors [65, 66], where it was shown that, in many organic mate- (OTFTs). Easier solution printing of the organic materials rials, although the intrinsic electron and hole mobilities at low temperatures on even fairly larger area substrates may be comparable, their drastically reduced values, without using a high vacuum system [24–28] is well worth measured experimentally, may be the result of external considering, where various processes including screen influences of the traps or instabilities introduced by water, [29], ink-jet [30–33], and microcontact [34, 35] printings hydroxyl groups, or oxygen exposures [67, 68]. This exter- have been especially advanced for flexible and transparent nal influence on intrinsic charge carrier mobilities was device fabrications [36–39] employing plastic substrates further illustrated in the case of SiO2 gate dielectric that offering practically feasible integration of LEDs and organic carried a large density of hydroxyl groups on its surface, photovoltaic (OPV) solar cells on the same substrate. which acted as traps for injected electrons into the Knowing that a single-crystal semiconductor is an channel. However, the process of covering the dielectric ideal platform for studying and exploiting the intrin- with BCB resulted in good electron transport in materials sic charge carrier transport properties, extensive efforts such as polythiophene, polyfluorene, and polyparaphe- were put in to grow crystalline OS [40–43] and succes- nylene-vinylene with charge carrier mobilities in the range sive improvements achieved in material crystallinity did of 10-2 to 10-3 cm2/Vs [23]. show significant improvement in the charge carrier mobil- Small organic molecules for device applications ity. For example, very low values of the mobilities, meas- include polycyclic aromatic hydrocarbons, fused heterocy- ured in earlier samples, in the range of 0.001 to 0.1 cm2/Vs clic aromatic compounds, oligothiophenes, oligoarylenes, [44] were pushed to as high as 20 cm2/Vs in crystalline and macrocycles such as phthalocyanines, fullerenes, ruberene and pentacene samples at room temperature. and perylene pigments along with perylene and vio- Still higher mobility of 400 cm2/Vs was measured in naph- lanthrone as electron
Load more

Recommended publications
  • Refining Crude Oil
    REFINING CRUDE OIL New Zealand buys crude oil from overseas, as well as drilling for some oil locally. This oil is a mixture of many hydrocarbons that has to be refined before it can be used for fuel. All crude oil in New Zealand is refined by The New Zealand Refining Company at their Marsden Point refinery where it is converted to petrol, diesel, kerosene, aviation fuel, bitumen, refinery gas (which fuels the refinery) and sulfur. The refining process depends on the chemical processes of distillation (separating liquids by their different boiling points) and catalysis (which speeds up reaction rates), and uses the principles of chemical equilibria. Chemical equilibrium exists when the reactants in a reaction are producing products, but those products are being recombined again into reactants. By altering the reaction conditions the amount of either products or reactants can be increased. Refining is carried out in three main steps. Step 1 - Separation The oil is separated into its constituents by distillation, and some of these components (such as the refinery gas) are further separated with chemical reactions and by using solvents which dissolve one component of a mixture significantly better than another. Step 2 - Conversion The various hydrocarbons produced are then chemically altered to make them more suitable for their intended purpose. For example, naphthas are "reformed" from paraffins and naphthenes into aromatics. These reactions often use catalysis, and so sulfur is removed from the hydrocarbons before they are reacted, as it would 'poison' the catalysts used. The chemical equilibria are also manipulated to ensure a maximum yield of the desired product.
    [Show full text]
  • General Disclaimer One Or More of the Following Statements May Affect
    General Disclaimer One or more of the Following Statements may affect this Document This document has been reproduced from the best copy furnished by the organizational source. It is being released in the interest of making available as much information as possible. This document may contain data, which exceeds the sheet parameters. It was furnished in this condition by the organizational source and is the best copy available. This document may contain tone-on-tone or color graphs, charts and/or pictures, which have been reproduced in black and white. This document is paginated as submitted by the original source. Portions of this document are not fully legible due to the historical nature of some of the material. However, it is the best reproduction available from the original submission. Produced by the NASA Center for Aerospace Information (CASI) NASA CR - 159480 EXXON/GRUS. 1KWD. 78 NIGH PERFORMANCE, HIGH DENSITY HYDROCARBON FUELS J. W. Frankenfeld, T. W. Hastings, M. Lieberman and W. F. Taylor EXXON RESEARCH AND ENGINEERING COMPANY prepared for NATIONAL AERONAUTICS AND SPACE ADMINISTRATION (NASA-CR-159''PO) HIGH PEPPOFMANCF, HIGH V79-20267 DENSTTv HYDR I-CARBON FTIELS (Exxon P.esearch and Engineering Co.) 239 rp HC A11/MF A01 CSCL 21D 'Inclas G3/28 19456 NASA Lewis Research Center Contract NAS 3-20394 Qnr{l,,Y^ ^'Pr I€ ^i NASA CR - 159480 EXXON/GRUS . 1KWD . 78 L: HIGH PERFORMANCE, HIGH DENSITY HYDROCARBON FUELS J. W. Frankenfeld, T. W. Hastings, M. Lieberman and W. F. Taylor EXXON RESEARCH AND ENGINEERING COMPANY prepared for NATIONAL AERONAUTICS AND SPACE ADMINISTRATION NASA Lewis Research Center Contract NAS 3-20394 FOREWARD The research described in this report was performed at Exxon Research and Engineering Company, Linden, New Jersey and Contract NAS 320394 with Mr.
    [Show full text]
  • Polycyclic Aromatic Hydrocarbon Structure Index
    NIST Special Publication 922 Polycyclic Aromatic Hydrocarbon Structure Index Lane C. Sander and Stephen A. Wise Chemical Science and Technology Laboratory National Institute of Standards and Technology Gaithersburg, MD 20899-0001 December 1997 revised August 2020 U.S. Department of Commerce William M. Daley, Secretary Technology Administration Gary R. Bachula, Acting Under Secretary for Technology National Institute of Standards and Technology Raymond G. Kammer, Director Polycyclic Aromatic Hydrocarbon Structure Index Lane C. Sander and Stephen A. Wise Chemical Science and Technology Laboratory National Institute of Standards and Technology Gaithersburg, MD 20899 This tabulation is presented as an aid in the identification of the chemical structures of polycyclic aromatic hydrocarbons (PAHs). The Structure Index consists of two parts: (1) a cross index of named PAHs listed in alphabetical order, and (2) chemical structures including ring numbering, name(s), Chemical Abstract Service (CAS) Registry numbers, chemical formulas, molecular weights, and length-to-breadth ratios (L/B) and shape descriptors of PAHs listed in order of increasing molecular weight. Where possible, synonyms (including those employing alternate and/or obsolete naming conventions) have been included. Synonyms used in the Structure Index were compiled from a variety of sources including “Polynuclear Aromatic Hydrocarbons Nomenclature Guide,” by Loening, et al. [1], “Analytical Chemistry of Polycyclic Aromatic Compounds,” by Lee et al. [2], “Calculated Molecular Properties of Polycyclic Aromatic Hydrocarbons,” by Hites and Simonsick [3], “Handbook of Polycyclic Hydrocarbons,” by J. R. Dias [4], “The Ring Index,” by Patterson and Capell [5], “CAS 12th Collective Index,” [6] and “Aldrich Structure Index” [7]. In this publication the IUPAC preferred name is shown in large or bold type.
    [Show full text]
  • High-Throughput Investigation of the Geometry and Electronic Structures
    Subscriber access provided by FRITZ HABER INST DER MPI Article High-Throughput Investigation of the Geometry and Electronic Structures of Gas-Phase and Crystalline Polycyclic Aromatic Hydrocarbons Bohdan Schatschneider, Stephen Monaco, Jian-Jie Liang, and Alexandre Tkatchenko J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/jp5064462 • Publication Date (Web): 07 Aug 2014 Downloaded from http://pubs.acs.org on August 12, 2014 Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
    [Show full text]
  • Chemistry of Acenes, [60]Fullerenes, Cyclacenes and Carbon Nanotubes
    University of New Hampshire University of New Hampshire Scholars' Repository Doctoral Dissertations Student Scholarship Spring 2011 Chemistry of acenes, [60]fullerenes, cyclacenes and carbon nanotubes Chandrani Pramanik University of New Hampshire, Durham Follow this and additional works at: https://scholars.unh.edu/dissertation Recommended Citation Pramanik, Chandrani, "Chemistry of acenes, [60]fullerenes, cyclacenes and carbon nanotubes" (2011). Doctoral Dissertations. 574. https://scholars.unh.edu/dissertation/574 This Dissertation is brought to you for free and open access by the Student Scholarship at University of New Hampshire Scholars' Repository. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of University of New Hampshire Scholars' Repository. For more information, please contact [email protected]. CHEMISTRY OF ACENES, [60]FULLERENES, CYCLACENES AND CARBON NANOTUBES BY CHANDRANI PRAMANIK B.Sc., Jadavpur University, Kolkata, India, 2002 M.Sc, Indian Institute of Technology Kanpur, India, 2004 DISSERTATION Submitted to the University of New Hampshire in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Materials Science May 2011 UMI Number: 3467368 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. UMI Dissertation Publishing UMI 3467368 Copyright 2011 by ProQuest LLC. All rights reserved. This edition of the work is protected against unauthorized copying under Title 17, United States Code. ProQuest LLC 789 East Eisenhower Parkway P.O.
    [Show full text]
  • Excited States of Molecules with Density Functional Theory and Many Body Perturbation Theory
    Excited States of Molecules with Density Functional Theory and Many Body Perturbation Theory by Samia M. Hamed A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Chemistry in the Graduate Division of the University of California, Berkeley Committee in charge: Professor Jeffrey B. Neaton, Chair Professor Martin Head-Gordon, Co-chair Professor Naomi Ginsberg Professor Michael F. Crommie Summer 2020 Excited States of Molecules with Density Functional Theory and Many Body Perturbation Theory Copyright 2020 by Samia M. Hamed 1 Abstract Excited States of Molecules with Density Functional Theory and Many Body Perturbation Theory by Samia M. Hamed Doctor of Philosophy in Chemistry University of California, Berkeley Professor Jeffrey B. Neaton, Chair Professor Martin Head-Gordon, Co-chair The accurate prediction of electronic excitation energies in molecules is an area of intense research of significant fundamental interest and is critical for many applications. Today, most excited state calculations use time-dependent density functional theory (TDDFT) in conjunction with an approximate exchange-correlation functional. In this dissertation, I have examined and critically assessed an alternative method for predicting charged and low-lying neutral excitations with similar computational cost: the ab initio Bethe-Salpeter equation (BSE) approach. Rigorously based on many-body Green's function theory but incorporating information from density functional theory, the predictive power of the BSE approach remained at the beginning of this work unexplored for the neutral and charged electronic excitations of organic molecules. Here, the results and implications of several systematic benchmarks are laid out in detail. i Contents Contents i List of Figures iii List of Tables vii 1 Electronic excited state calculations in molecules: challenges and oppor- tunities 1 1.1 Case Study 1: Biomimetic light harvesting complexes .
    [Show full text]
  • Spectroscopic Study of Anisotropic Excitons in Single Crystal Hexacene † † ‡ ‡ ‡ † Alexey Chernikov,*, Omer Yaffe, Bharat Kumar, Yu Zhong, Colin Nuckolls, and Tony F
    Letter pubs.acs.org/JPCL Spectroscopic Study of Anisotropic Excitons in Single Crystal Hexacene † † ‡ ‡ ‡ † Alexey Chernikov,*, Omer Yaffe, Bharat Kumar, Yu Zhong, Colin Nuckolls, and Tony F. Heinz*, † Departments of Physics and Electrical Engineering, Columbia University, New York, New York 10027, United States ‡ Department of Chemistry, Columbia University, New York, New York 10027, United States *S Supporting Information ABSTRACT: The linear optical response of hexacene single crystals over a spectral range of 1.3−1.9 eV was studied using polarization-resolved reflectance spectroscopy at cryogenic temperatures. We observe strong polarization anisotropy for all optical transitions. Pronounced deviations from the single-molecule, solution-phase spectra are present, with a measured Davydov splitting of 180 meV, indicating strong intermolecular coupling. The energies and oscillator strengths of the relevant optical transitions and polarization-dependent absorption coefficients are extracted from quantitative analysis of the data. SECTION: Spectroscopy, Photochemistry, and Excited States inear acenes, that is, naphthalene, anthracene, tetracene, established between the degree of CT character and the so- L and pentacene, form a unique family of organic semi- called Davydov splitting (DS)19 of the low-lying excitons conductors. These materials readily form large (>100 μm2) observed in polarization-resolved optical absorption spectra.6 single crystals that exhibit a “herring-bone” packing motif in Thus, experimental characterization of the intrinsic optical 1 which aromatic edge-to-face interactions dominate. During the properties of organic crystals also facilitates rational design of last few decades, this family has been the subject of many advanced optoelectronic devices. Naturally, the steady increase 2 experimental and theoretical studies, especially motivated by of the intermolecular coupling from naphthalene to pentacene fl potential applications in exible, low-cost optoelectronic crystals provides a strong impetus for a systematic study of even 3−5 devices.
    [Show full text]
  • WO 2016/074683 Al 19 May 2016 (19.05.2016) W P O P C T
    (12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (19) World Intellectual Property Organization International Bureau (10) International Publication Number (43) International Publication Date WO 2016/074683 Al 19 May 2016 (19.05.2016) W P O P C T (51) International Patent Classification: (81) Designated States (unless otherwise indicated, for every C12N 15/10 (2006.01) kind of national protection available): AE, AG, AL, AM, AO, AT, AU, AZ, BA, BB, BG, BH, BN, BR, BW, BY, (21) International Application Number: BZ, CA, CH, CL, CN, CO, CR, CU, CZ, DE, DK, DM, PCT/DK20 15/050343 DO, DZ, EC, EE, EG, ES, FI, GB, GD, GE, GH, GM, GT, (22) International Filing Date: HN, HR, HU, ID, IL, IN, IR, IS, JP, KE, KG, KN, KP, KR, 11 November 2015 ( 11. 1 1.2015) KZ, LA, LC, LK, LR, LS, LU, LY, MA, MD, ME, MG, MK, MN, MW, MX, MY, MZ, NA, NG, NI, NO, NZ, OM, (25) Filing Language: English PA, PE, PG, PH, PL, PT, QA, RO, RS, RU, RW, SA, SC, (26) Publication Language: English SD, SE, SG, SK, SL, SM, ST, SV, SY, TH, TJ, TM, TN, TR, TT, TZ, UA, UG, US, UZ, VC, VN, ZA, ZM, ZW. (30) Priority Data: PA 2014 00655 11 November 2014 ( 11. 1 1.2014) DK (84) Designated States (unless otherwise indicated, for every 62/077,933 11 November 2014 ( 11. 11.2014) US kind of regional protection available): ARIPO (BW, GH, 62/202,3 18 7 August 2015 (07.08.2015) US GM, KE, LR, LS, MW, MZ, NA, RW, SD, SL, ST, SZ, TZ, UG, ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, RU, (71) Applicant: LUNDORF PEDERSEN MATERIALS APS TJ, TM), European (AL, AT, BE, BG, CH, CY, CZ, DE, [DK/DK]; Nordvej 16 B, Himmelev, DK-4000 Roskilde DK, EE, ES, FI, FR, GB, GR, HR, HU, IE, IS, IT, LT, LU, (DK).
    [Show full text]
  • Arxiv:1604.00041V1 [Cond-Mat.Mtrl-Sci] 31 Mar 2016
    , Structural and excited-state properties of oligoacene crystals from first principles 1, 2, 3 4, 1 1, 5 Tonatiuh Rangel, ∗ Kristian Berland, Sahar Sharifzadeh, Florian Brown-Altvater, Kyuho Lee,1 Per Hyldgaard,6, 7 Leeor Kronik,8 and Jeffrey B. Neaton1, 2, 9 1Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720,USA 2Department of Physics, University of California, Berkeley, California 94720-7300, USA 3Centre for Material Science and Nanotechnology, University of Oslo, NO-0316 Oslo, Norway 4Department of Electrical and Computer Engineering and Division of Materials Science and Engineering, Boston University, Boston, MA 02215, USA 5Department of Chemistry, University of California, Berkeley, California 94720-7300, USA 6Department of Microtechnology and Nanoscience, MC2, Chalmers University of Technology,SE-41296 G¨oteborg, Sweden 7Materials Science and Applied Mathematics, Malm¨oUniversity, Malm¨oSE-205 06, Sweden 8Department of Materials and Interfaces, Weizmann Institute of Science, Rehovoth 76100, Israel 9Kavli Energy NanoSciences Institute at Berkeley, Berkeley, California 94720-7300, USA (Dated: March 27, 2018) Molecular crystals are a prototypical class of van der Waals (vdW)-bound organic materials with excited state properties relevant for optoelectronics applications. Predicting the structure and excited state properties of molecular crystals presents a challenge for electronic structure theory, as standard approximations to density functional theory (DFT) do not capture long-range vdW dispersion interactions and do not yield excited-state properties. In this work, we use a combination of DFT including vdW forces{ using both non-local correlation functionals and pair-wise correction methods { together with many-body perturbation theory (MBPT) to study the geometry and excited states, respectively, of the entire series of oligoacene crystals, from benzene to hexacene.
    [Show full text]
  • The Pennsylvania State University the Eberly College of Science
    The Pennsylvania State University The Eberly College of Science Department of Chemistry SYNTHESIS OF CARBON MATERIALS VIA THE COLD COMPRESSION OF AROMATIC MOLECULES AND CARBON NANOSTRUCTURES A Dissertation in Chemistry by Thomas C. Fitzgibbons 2014 Thomas C. Fitzgibbons Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy August 2014 ii The dissertation of Thomas C. Fitzgibbons was reviewed and approved* by the following: John V. Badding Professor of Chemistry Dissertation Advisor Chair of Committee Ayusman Sen Distinguished Professor of Chemistry A. Welford Castleman, Jr Evan Pugh Professor of Chemistry and Physics William B. White Professor Emeritus of Geosciences Barbara J. Garrison Shapiro Professor of Chemistry Head of the Department of Chemistry *Signatures are on file in the Graduate School iii ABSTRACT Carbon’s ability for catenation makes it a remarkable element and allows for many interesting and surprising properties and structures. Carbon can exist in one of its two thermodynamically stable bulk crystals, graphite or diamond, one of its several nanostructures: fullerene, nanotube, or graphene, or as an amorphous material with a mixed bonding pattern. Carbon also has an ability to bond heteroatoms such as hydrogen which can increase its properties and structures even further. Pressure has been shown to be able to drastically change the bonding in and structure of carbon based materials. In this dissertation I will present how pressure can be used to synthesize new amorphous hydrogenated carbons and how a battery of analytical techniques can be used to elicit the microstructure of the carbon networks. This microstructure can then be related back to the reaction conditions and more importantly the starting small molecule.
    [Show full text]
  • A Systematic (Time-Dependent) Density Functional Theory Study
    Electronic and optical properties of families of polycyclic aromatic hydrocarbons: a systematic (time-dependent) density functional theory study G. Malloci a,∗, G. Cappellini a,b, G. Mulas b, A. Mattoni a aCNR–IOM and Dipartimento di Fisica, Universit`adegli Studi di Cagliari, Cittadella Universitaria, Strada Prov. le Monserrato–Sestu Km 0.700, I–09042 Monserrato (CA), Italy bINAF – Osservatorio Astronomico di Cagliari–Astrochemistry Group, Strada 54, Localit`aPoggio dei Pini, I–09012 Capoterra (CA), Italy Abstract Homologous classes of Polycyclic Aromatic Hydrocarbons (PAHs) in their crys- talline state are among the most promising materials for organic opto-electronics. Following previous works on oligoacenes we present a systematic comparative study of the electronic, optical, and transport properties of oligoacenes, phenacenes, cir- cumacenes, and oligorylenes. Using density functional theory (DFT) and time- dependent DFT we computed: (i) electron affinities and first ionization energies; (ii) quasiparticle correction to the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap; (iii) molecular reorganization energies; (iv) electronic absorption spectra of neutral and ±1 charged systems. The excitonic effects are estimated by comparing the optical gap and the quasiparticle corrected HOMO-LUMO energy gap. For each molecular property computed, general trends as a function of molecular size and charge state are discussed. Overall, we find that circumacenes have the best transport properties, displaying a steeper decrease of the molecular reorganization energy at increasing sizes, while oligorylenes are much arXiv:1104.2978v1 [cond-mat.mtrl-sci] 15 Apr 2011 more efficient in absorbing low–energy photons in comparison to the other classes. Key words: PAHs, Electronic absorption, Charge–transport, Density functional theory, Time–dependent density functional theory ∗ Corresponding author.
    [Show full text]
  • Chemical Stability and Performance Influence of Choice Substituents and Core Conjugation of Organic Semiconductors
    University of Massachusetts Amherst ScholarWorks@UMass Amherst Doctoral Dissertations Dissertations and Theses March 2019 CHEMICAL STABILITY AND PERFORMANCE INFLUENCE OF CHOICE SUBSTITUENTS AND CORE CONJUGATION OF ORGANIC SEMICONDUCTORS Jack Ly University of Massachusetts Amherst Follow this and additional works at: https://scholarworks.umass.edu/dissertations_2 Part of the Polymer and Organic Materials Commons, Polymer Science Commons, and the Semiconductor and Optical Materials Commons Recommended Citation Ly, Jack, "CHEMICAL STABILITY AND PERFORMANCE INFLUENCE OF CHOICE SUBSTITUENTS AND CORE CONJUGATION OF ORGANIC SEMICONDUCTORS" (2019). Doctoral Dissertations. 1516. https://doi.org/10.7275/13323135 https://scholarworks.umass.edu/dissertations_2/1516 This Open Access Dissertation is brought to you for free and open access by the Dissertations and Theses at ScholarWorks@UMass Amherst. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of ScholarWorks@UMass Amherst. For more information, please contact [email protected]. CHEMICAL STABILITY AND PERFORMANCE INFLUENCE OF CHOICE SUBSTITUENTS AND CORE CONJUGATION OF ORGANIC SEMICONDUCTORS A Dissertation Presented By JACK THANH LY Submitted to the Graduate School of the University of Massachusetts Amherst in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY February 2019 Polymer Science and Engineering © Copyright by Jack Thanh Ly 2019 All Rights Reserved CHEMICAL STABILITY AND PERFORMANCE INFLUENCE OF CHOICE
    [Show full text]