No description available.

In the last three decades Organic Electronics emerged and established itself as an interdisciplinary field of science and as part of our daily life. Presently, the greatest scientific challenges in this field of research are two: the former relies on the improvement of devices efficiency which can be accomplished by using new materials, whereas the latter consist in the integration of multiple functionalities in a single device. To accomplish these goals one needs to develop a deep understanding on the fundamental physical-chemistry ruling the properties which are on the basis of organic electronics such as charge injection, charge transfer and transport. This PhD project reports the developing of efficient multicomponent electroactive self-assembled systems whose electro- and optical properties can be modulated, in devices, as a response to multiple external and independent stimuli. This goal has been achieved by engineering of the proper building blocks and the study of the the physico-chemical properties to be able to model all the mechanisms involved.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

elementares da eletrônica orgânica, vêm sendo desenvolvidos e integrados para realização de dispositivos eletrônicos de baixo custo, alto volume e flexíveis. Nesta tese foi proposta uma tecnologia para a construção de OFETs sobre substrato flexível e a caracterização destes dispositivos foi feita. Transistores com diferentes comprimentos de canal (L= 5, 10, 20 e 40 μm) foram construídos e avaliados. As características e configuração do poli (álcool vinílico) (PVA) como dielétrico de porta foram definidas através da otimização da reticulação, grau de hidrólise e peso molecular. O PVA utilizado como dielétrico de porta foi de alto peso molecular, hidrolização incompleta e reticulado com dicromato de amônia. O desafio de compatibilização entre os filmes de PVA e poli (3-hexiltiofeno) (P3HT) com diferentes polaridades foi superado e abriu caminho para construção de OFETs e capacitores, estes últimos usados para extrair a capacitância por unidade de área do conjunto PVA-P3HT. Os processos desenvolvidos de fotolitografia e de oxidação por plasma de oxigênio possibilitaram a construção de transistores flexíveis inéditos de Ni-P3HT-PVA-Al com uma arquitetura top-gate, bottom-contacts. Os transistores apresentaram boas características de saída, baixa tensão de operação (< |-6 V|), boa mobilidade (0,015 cm2/V*s) e razões ION/IOFF aceitáveis (~300). A resistência de contato e mobilidade efetiva foram obtidas através do método de linhas de transmissão. Uma boa estabilidade temporal foi atingida, porém ocorreram instabilidades na operação quando os transistores foram testados. A corrente do transistor não se manteve estável, primeiramente aumentou e depois diminuiu com a realização de sucessivas medidas. As razões deste comportamento foram discutidas. Inversores foram demonstrados e caracterizados. O aperfeiçoamento da tecnologia desenvolvida possibilitará a construção de circuitos orgânicos analógicos e digitais para aplicações cotidianas que demandem baixo custo e alto volume. / Organic field effect transistors (OFETs), the elementary components of organic electronics, are constantly developed and integrated to realize low cost, high volume, flexible electronic devices. In this thesis a technology for creating OFETs on flexible substrates is proposed and their characterization is performed. Flexible transistors with different channel lengths (L= 5, 10, 20 and 40 μm) were built and evaluated. The characteristics and configurations of the poly (vinyl alcohol) (PVA) as gate dielectric were defined through the optimization of crosslinking, the degree of hydrolysis and the molecular weight. The chosen PVA is cross-linked with ammonium dichromate, has a high molecular weight and incomplete hydrolization. The challenge of integrating polymers of different polarities: PVA and poly (3-hexyl thiophene) (P3HT), the chosen organic semiconductor, was overcome and opened a path to the construction of OFETs and capacitors. From the later capacitance per unit area was extracted. The developed processes of photolithography and oxygen plasma etching allowed the construction of unprecedented Ni-P3HT-PVA-Al flexible top-gate, bottomcontacts transistors. The transistors showed good output characteristics, low operation voltages (< |-6 V|), acceptable carrier mobilities (0,015 cm2/V*s) and ION/IOFF fractions (~300). Contact resistance and effective mobility were extracted through transmission line method. The transistors showed great temporal stability, but when operated instabilities occurred. The transistor output current first increased and later degraded with successive testing. Organic PMIS inverters were demonstrated and characterized. The optimization of this technology may lead to construction of flexible logic organic devices for everyday applications.

elementares da eletrônica orgânica, vêm sendo desenvolvidos e integrados para realização de dispositivos eletrônicos de baixo custo, alto volume e flexíveis. Nesta tese foi proposta uma tecnologia para a construção de OFETs sobre substrato flexível e a caracterização destes dispositivos foi feita. Transistores com diferentes comprimentos de canal (L= 5, 10, 20 e 40 μm) foram construídos e avaliados. As características e configuração do poli (álcool vinílico) (PVA) como dielétrico de porta foram definidas através da otimização da reticulação, grau de hidrólise e peso molecular. O PVA utilizado como dielétrico de porta foi de alto peso molecular, hidrolização incompleta e reticulado com dicromato de amônia. O desafio de compatibilização entre os filmes de PVA e poli (3-hexiltiofeno) (P3HT) com diferentes polaridades foi superado e abriu caminho para construção de OFETs e capacitores, estes últimos usados para extrair a capacitância por unidade de área do conjunto PVA-P3HT. Os processos desenvolvidos de fotolitografia e de oxidação por plasma de oxigênio possibilitaram a construção de transistores flexíveis inéditos de Ni-P3HT-PVA-Al com uma arquitetura top-gate, bottom-contacts. Os transistores apresentaram boas características de saída, baixa tensão de operação (< |-6 V|), boa mobilidade (0,015 cm2/V*s) e razões ION/IOFF aceitáveis (~300). A resistência de contato e mobilidade efetiva foram obtidas através do método de linhas de transmissão. Uma boa estabilidade temporal foi atingida, porém ocorreram instabilidades na operação quando os transistores foram testados. A corrente do transistor não se manteve estável, primeiramente aumentou e depois diminuiu com a realização de sucessivas medidas. As razões deste comportamento foram discutidas. Inversores foram demonstrados e caracterizados. O aperfeiçoamento da tecnologia desenvolvida possibilitará a construção de circuitos orgânicos analógicos e digitais para aplicações cotidianas que demandem baixo custo e alto volume. / Organic field effect transistors (OFETs), the elementary components of organic electronics, are constantly developed and integrated to realize low cost, high volume, flexible electronic devices. In this thesis a technology for creating OFETs on flexible substrates is proposed and their characterization is performed. Flexible transistors with different channel lengths (L= 5, 10, 20 and 40 μm) were built and evaluated. The characteristics and configurations of the poly (vinyl alcohol) (PVA) as gate dielectric were defined through the optimization of crosslinking, the degree of hydrolysis and the molecular weight. The chosen PVA is cross-linked with ammonium dichromate, has a high molecular weight and incomplete hydrolization. The challenge of integrating polymers of different polarities: PVA and poly (3-hexyl thiophene) (P3HT), the chosen organic semiconductor, was overcome and opened a path to the construction of OFETs and capacitors. From the later capacitance per unit area was extracted. The developed processes of photolithography and oxygen plasma etching allowed the construction of unprecedented Ni-P3HT-PVA-Al flexible top-gate, bottomcontacts transistors. The transistors showed good output characteristics, low operation voltages (< |-6 V|), acceptable carrier mobilities (0,015 cm2/V*s) and ION/IOFF fractions (~300). Contact resistance and effective mobility were extracted through transmission line method. The transistors showed great temporal stability, but when operated instabilities occurred. The transistor output current first increased and later degraded with successive testing. Organic PMIS inverters were demonstrated and characterized. The optimization of this technology may lead to construction of flexible logic organic devices for everyday applications.

Existem algumas técnicas destinadas ao estudo das características fotofísicas de materiais orgânicos ou dispositivos eletrônicos e optoeletrônicos a base de semicondutores orgânicos. A exemplo disso, a técnica de espectroscopia de absorção fotoinduzida de onda contínua (Continuous Wave Photoinduced Absorption/cw-PIA) apresenta grande sensibilidade como método destinado ao estudo dos processos eletrônicos envolvendo espécies excitadas de vida longa. Esta técnica emprega dois feixes ópticos distintos, um para excitação da amostra e outro (feixe de prova) para investigar os estados excitados remanescentes em amostra após bombeio óptico. O presente trabalho tem como objetivo a construção, desenvolvimento e caracterização de um aparato experimental para espectroscopia cw-PIA. A montagem bem sucedida da técnica foi testada em filme do polímero semicondutor P3HT, em filme de blenda (1:1) de P3HT/PCBM (comumente utilizada como camada ativa em células solares orgânicas) e em filmes automontados camada-a-camada (LbL) do tipo doador-aceitador de carga (P3KHT/P6N), sendo que a molécula P6N foi sintetizada pelo Grupo de Polímeros Bernhard Gross do IFSC-USP. Os filmes LbL de P3KHT/P6N, em comparação aos filmes blenda de P3HT/PCBM, demonstraram uma eficiência maior quanto a geração de portadores de carga com tempo de vida longo. / There are some techniques for the study of photophysical characteristics of organic materials or electronic and optoelectronic devices based on organic semiconductors. For example, the technique of continuous wave photoinduced absorption spectroscopy (cw-PIA) is a highly sensitive method for the study of the electronic processes involving long-lived excited species. This technique uses two distinct optical beams, one for sample excitation and another for probing the excited states remaining in the sample after optical pumping. The present work aims at the construction, development and characterization of an experimental apparatus for cw-PIA spectroscopy. The successful implementation of the technique was tested in a film of the semiconducting polymer P3HT and of the blend (1:1) P3HT/ PCBM (usually employed as active layer in organic solar cells), and also in a Layer-by-Layer (LbL) film of donor-acceptor molecules P3KHT/P6N, where the P6N molecule has been synthesized by Polymer Group Bernhard Gross at IFSC- USP. The comparison between P3KHT / P6N LbL film and the blend P3HT/PCBM has demonstrated higher charge carrier generation efficiency (with long lifetime) for the LbL film.

Dans ce travail, différentes solutions aqueuses de PEDOT: polyelectrolyte ont été synthétisées à partir de polymères anioniques de types polysaccharides et polystyrènes substitués par des groupements bis(sulfonylimide). Leurs morphologies, dopages,comportements rhéologiques ainsi que leurs propriétés opto-électroniques ont notammen tété caractérisés. Une étude systématique a révélé que les polyélectrolytes de masse molaire élevée portant un groupement fortement acide et ayant un squelette rigide permettent d'obtenir un dopage élevé, une dispersion efficace du PEDOT et donc des complexes PEDOT : polyelectrolyte plus conducteurs. L'utilisation du polyelectrolyte PSTFSI en tant qu'agent de complexation pour le PEDOT donne une dispersion stable montrant les caractéristiques d'un gel, ce qui facilite la fabrication de films minces par 'spin coating' ou doctor blade. Les films de PEDOT : PSTFSI ainsi obtenus montrent une transparence élevée et une conductivité de 330S.cm-1. Ces propriétés ont permis de les intégrer avec succès comme matériaux d'électrodes dans des dispositifs OLED, OPV et OECT. / In this work different aqueous dispersions of conducting poly(3,4-ethylenedioxythiophene) :polyelectrolyte (PEDOT:polyelectrolyte) complexes,made from anionic polysaccharides and from synthetic bis(sulfonylimide) substituted polystyrenes, have been synthesized and characterized regarding their doping, morphology, rheological behavior and opto-electronic properties. A systematic study revealed, that high molar mass polyelectrolytes with strongly acidic groups and a rigid backbone structure were favorable for a high doping and an efficient dispersion of PEDOT and allowed the development of highly conducting PEDOT:polyelectrolyte complexes. The use of the polyelectrolyte poly(4-styrenetrifluoromethane(bissulfonylimide)) (PSTFSI) as complexing agent for PEDOT resultedin stable dispersions with gel character, which allowed easy processing by spin coating and doctor blading. The obtained PEDOT:PSTFSI films were highly transparent,displayed a conductivity of up to 330S.cm-1 and were successfully integrated as electrodes in OLED, OPV and OECT devices.

No description available.

Initial research in the field of organic electronics focused primarily on the improvements in material performance. Significant progress has been achieved in the case of organic field effect transistors, where reported mobility values are now over 5 orders of magnitude higher than those of early devices. As a consequence, the use of organic transistors is now being considered for real-world applications in the form of integrated logic circuits. This in turn presents many new challenges, as the logic circuit requirements are more demanding on the transistor characteristics and corresponding fabrication processes. This thesis investigates the feasibility of organic technology for its potential use in future low-cost, high-volume electronic applications. The research objectives were accomplished by practical evaluation of an organic logic circuit fabrication process. First, recent advances in the fabrication of organic circuits in terms of transistor structure, material usage and fabrication techniques are reviewed. Next, a lithographic logic circuit fabrication process using PVP gate dielectric and TIPS-pentacene organic semiconductor adapted from state of the art fabrication process is presented. The logic circuit design decisions and the methodology for the fabrication process are thoroughly documented. Using this process, zero-Vgs and diode-load inverter circuits were successfully fabricated. However, the process is in need of further refinement for more complex circuit designs, as the fabrication of a comparator circuit consisting of 11 transistors was unsuccessful. Two optimisation techniques that are compatible with the logic circuit fabrication process were also explored in this work. To improve the capacitive coupling of the dielectric layer, the use of a polymer nanocomposite dielectric was investigated. The nanocomposite is prepared by blending PVP solution with a high-k inorganic nanoparticle filler, barium strontium titanate. Using the nanocomposite dielectric, both single transistors and integrated logic circuits were successfully fabricated. This is the first report on the use of PVP and barium strontium titanate nanocomposite dielectric with a lithographic based logic circuit fabrication process. The use of PFBT modified Au contacts for the fabrication process was investigated to improve theperformance of the contact electrode layer. Using PFBT, mobility increased by one order of magnitude over untreated Au electrodes for the PVP and TIPS-pentacene transistors.

Organická elektronika je dynamické, rychle se rozvíjející odvětví. Studium nových materiálů pro organickou elektroniku je důležitým úkolem jak z hlediska výkonnosti budoucích zařízení a ekonomičnosti procesů, tak z hlediska vlivu jejich používání na životní prostředí. Deriváty diketopyrrolopyrrolu patří mezi zajímavé materiály, které jsou v posledních letech studovány s ohledem na využití v organické elektronice. Dizertační práce je zaměřena na studium těchto materiálů a jejich jak optickou, tak i elektrickou charakterizaci. Součástí je také zhodnocení jejich potenciální aplikace v organické elektronice a návrhy optimalizace jejich výkonu. Teoretická část práce popisuje současný stav na poli organické elektroniky zaměřený na materiály na bázi diketopyrrolopyrrolu. Následující výsledková část shrnuje podstatné výsledky práce a obsahuje stručný úvod k přiloženým publikacím, včetně zhodnocení vlastního přínosu autora k jednotlivým publikacím. Výsledková část dále sestává z 6 vědeckých publikací, které jsou nedílnou součástí této práce a jsou tematicky propojeny v oblasti organické elektroniky, nových materiálů na bázi diketopyrrolopyrrolu a jejich aplikací. Z formálního hlediska je práce na základě čl. 42 odstavce 1b Studijního a zkušebního řádu VUT koncipovaná jako tematicky uspořádaný soubor uveřejněných prací a prací přijatých k publikaci.