L'objectif de ce travail de thèse est l'élaboration d'une photodiode organique (OPD) destinée à être intégrée dans un biocapteur. Ce travail s'inscrit dans le cadre plus général de l'étude et de l'amélioration de composants organiques impliqués dans des microsystèmes de détection visant à surveiller la pollution de l'eau. Le besoin d'évaluation et de suivi de la qualité de l'eau suscite un grand intérêt pour des systèmes de détection portables de polluants ayant une réponse rapide et de faible coût. Le principe de la mesure repose sur la détection des variations de fluorescence de micro-algues en présence de substances toxiques. Excitées grâce à une diode électroluminescente (LED) bleue, les algues vont émettre un signal de fluorescence dont l'intensité, modifiée en présence de polluant (Diuron), est détectée par l'OPD optimisée. Le signal de fluorescence à détecter étant très faible, l'OPD idéale doit avoir un faible courant d'obscurité et une grande sensibilité. Cela passe par un choix judicieux des matériaux semi-conducteurs organiques (OSC) entrant dans l'élaboration de la couche active du composant. Pour accompagner le choix des matériaux, il est intéressant d'explorer leurs propriétés physico-chimiques tout en essayant de rationaliser les mécanismes mis en jeu au sein de ces matériaux lorsqu'ils sont utilisés dans l'élaboration d'OPD (phénomènes d'absorption de photons, mécanismes de transport de charges, et pertes associées aux recombinaisons de charges). Cette thèse s'articule autour de deux axes. Le premier axe consiste en une étude théorique qui vise à comprendre et à maitriser l'échange des charges à l'échelle nanométrique par des caractérisations optiques et des calculs de chimie quantique basés sur des méthodes DFT et TD-DFT. L'étude sur un système modèle (le P3HT) a permis d'établir un protocole de calcul très prometteur pour l'étude des propriétés de matériau d'intérêt, en particulier le PTB7. Le second axe est un volet à caractère expérimental. L'élaboration, la caractérisation et l'optimisation d'OPD à base de PTB7 : PC60BM a permis de concevoir un biocapteur algal apte à détecter le Diuron à des concentrations de l'ordre du nanomolaire. / The aim of this thesis is to develop an organic photodiode (OPD) designed to be integrated into a biosensor. It is part of the broader framework of studying and improving organic components involved into devices devoted to water pollution monitoring. The need for such portable, fast-response, low-cost microsystems is of great interest. The measurement is based on the fluorescence detection of micro-algae under toxic substances exposure. The excited algae, under a blue light emitting diode (LED), will emit a fluorescence signal whose intensity, modified because of pollutant exposure (Diuron), is detected by the OPD. Since the fluorescence signal is very weak, the ideal OPD must have a low dark current and a high sensitivity. To achieve this performance, a judicious choice of organic semiconductor materials (OSC) used for the OPD is required. In addition, it is interesting to investigate their physico-chemical properties by rationalizing the mechanisms involved in the active layer (photon absorption phenomena, charge transport mechanisms, and losses associated with charge recombinations). This thesis is based on two axes. The first one consists in a theoretical study of the charge exchanges at a nanoscale. This have been done by both optical characterizations and quantum chemistry calculations based on DFT and TD-DFT methods. Calculations were performed on a model system (P3HT) thus providing the basis for a very promising computational protocol for studying the properties of materials of interest, for instance PTB7. The second axis concerns the experimental study of the OPD based on PTB7:PC60BM. We have developed, characterized and optimized an OPD guarantying the detection of algal fluorescence without and with Diuron at about nanomolar concentrations.

A importância da pesquisa em eletrônica orgânica, se comparada à microeletrônica convencional baseada principalmente em silício, surge pela presença de inúmeros semicondutores e técnicas de deposição de baixo custo e em grande superfície. Os Transistores de Filmes Finos Orgânicos (OTFTs, do inglês Organic Thin-Film Transistors) são a unidade fundamental em circuitos eletrônicos e, geralmente, apresentam a estrutura de um transistor de efeito de campo. Podem ser fabricados sobre substratos plásticos e oferecem grande número de aplicações como: mostradores, etiquetas de identificação por rádio frequência e eletrônica têxtil. Além disso, há demanda por componentes eletrônicos portáteis e baratos, principalmente como sensores em diagnósticos médicos e veterinários in-situ. A geometria de OTFT mais utilizada em sensores na atualidade é a bottom gate sobre substratos de silício altamente dopado e com óxido de porta inorgânico. Polímeros como poli(3-hexiltiofeno) (P3HT) vêm sendo amplamente utilizados pela comunidade científica, atestando o potencial comercial deste semicondutor em sensores. Neste contexto, esta tese apresenta o desenvolvimento de transistores à base de P3HT como sensores na detecção de analitos em fase vapor. O estudo é composto por uma etapa inicial de caracterização da mobilidade dos portadores de carga por técnicas de transiente de corrente, seguida pela otimização do desempenho de parâmetros elétricos do transistor através de alterações no processamento dos filmes dielétrico e semicondutor. Enfim, conclui-se a investigação através do entendimento dos fatores ligados à degradação do OTFT após exposição à atmosfera e sob estresse elétrico, além do detalhamento da sensibilidade e especificidade do sensor. Sensores de P3HT oferecem enorme potencial de detecção de amônia, cetonas e compostos organoclorados. Outros semicondutores poliméricos são provavelmente necessários para maior especificidade em relação a vapor dágua e álcoois. / Research on organic electronics, compared to conventional silicon-based microelectronics, is necessary as it offers plenty of semiconductors and low-cost deposition techniques that can be performed over wide surfaces. Organic Thin-Film Transistors (OTFTs) are the fundamental unity in electronic circuits and, usually, display the metal insulator semiconductor field-effect transistor (MISFET) structure. OTFTs can be processed over cheap plastic substrates and integrate a high number of applications as: flexible displays, radio frequency identification tags, textile electronics and sensors (e.g. chemical and biological compounds). Nowadays, consumers demand portable and low-cost electronic devices, mainly as sensors for in-situ medical and veterinarian diagnosis. The most widely used OTFT structure in sensing is the bottom-gate/bottom-contact FET over highly-doped silicon substrates and inorganic dielectrics. Polymers as poly(3-hexylthiophene) (P3HT) have found increasing acceptance by the scientific community, attesting their potential as semiconductors for commercial applications. In this context, the thesis lies in the development of organic transistors based in P3HT polymer for the detection of vapor-phase compounds. This study begins with transistor performance optimization through changes in dielectric and semiconductor processing. Thin-film thickness and P3HT cast solution drying time are the main studied parameters. It involves also the understanding of device performance degradation when exposed to atmosphere and under bias stress, before finally mapping sensitivity and specificity against gaseous analytes. P3HT-based sensors are potentially interesting for ammonia, ketones and organochlorides detection. Other polymeric semiconductors may be necessary to increase specificity against water steam and alcohol analytes.

A eletrônica digital desempenha papel essencial no desenvolvimento e manutenção dos padrões de vida em prática hoje no mundo. A peça fundamental para a criação desta era tecnológica é sem dúvidas o transistor. Com o advento de novos materiais, a busca por transistores que oferecem novas oportunidades de processamento e aplicação permitiu que uma nova área fosse criada: a eletrônica orgânica. Transistores de efeito de campo baseados em filmes finos de materiais orgânicos têm recebido grande atenção nas últimas décadas. Apresentamos um estudo experimental e teórico de transistores de efeito de campo a base de filmes finos orgânicos. Foram caracterizados transistores usando um derivado do pentaceno (TMTES-pentaceno) como camada ativa em um dispositivo feito sobre Si/SiO2. Mostramos que a inclusão do semicondutor orgânico em uma matriz polimérica isolante ajuda a manter a estabilidade termo mecânica do dispositivo. Foi desenvolvido um modelo que levasse em conta as resistências parasíticas para explicar o comportamento do transistor em função da temperatura. Também foram construídos e caracterizados transistores usando rr-P3HT como semicondutor e PMMA como isolantes. Apresentamos transistores do tipo Top-Gate e Bottom-Gate com mobilidade máxima de 7 x 10-3 cm2/V.s. Valores de razão ON/OFF de ~ 900 foram encontrados nos transistores otimizados. O comportamento dos transistores é analisado em função da temperatura e os modelos de aproximação de canal gradual e de Vissenberg-Matters foram aplicados para extração dos parâmetros de interesse. Por fim, apresentamos um modelo de corrente de canal baseado na resolução 2D numérica da equação de Poisson usando as idéias de Vissenberg-Matters para a concentração de cargas em função do potencial local. O modelo, embora ainda nos primeiros estágios de desenvolvimento, prevê a saturação da corrente nas curvas de saída simuladas sem limitações de regime de validade. / Digital electronics plays an essential role in the development and maintenance of living standards into practice in the world today. The cornerstone for the creation of this technological age is undoubtedly the transistor. With the advent of new materials, the search for transistors that offer new opportunities in processing and application allowed a new area to be created: the organic electronics. Field effect transistors based on organic thin films have received great attention in recent decades. We report an experimental and theoretical study of field effect transistors based on organic thin films. We characterized transistors manufactured using a derivative of pentacene (TMTES-pentacene) as the active layer in a device and using Si/SiO2 as gate and insulator. We show that the inclusion of the organic semiconductor in an insulating polymeric matrix helps to maintain the termo-mechanical stability of the device. A model was developed that take into account the parasitic resistances and to explain the behavior of the transistor as a function of temperature. We also present the manufacturing and characterization process of transistors using rr-P3HT as semiconductor and PMMA as insulator. We report Top-Gate and Bottom-Gate transistors with maximum mobility of 7 x 10-3 cm2/V.s. The maximun ON/OFF ratio of ~ 900 was found for the optimized transistors. The behavior of the transistors was analyzed as a function of temperature and both gradual channel approximation and Vissenberg-Matters models were applied for extracting the parameters. Finally, we present a channel current model based on the resolution of 2D numerical Poisson equation using the ideas of Vissenberg-Matters to the calculate the concentration of charges due to the local potential. The model, although still in the early stages of development, predicts the saturation current at output simulated curves with no limitation of regime validity.

A tecnologia dos semicondutores inorgânicos tem dominado a indústria eletrônica por muitos anos. No entanto, com a descoberta dos polímeros condutores um esforço considerável tem sido dedicado ao estudo e às aplicações tecnológicas desses materiais em dispositivos eletrônicos, dando início a um novo ramo da eletrônica: a Eletrônica Orgânica (EO). Uma das grandes vantagens da EO reside nos métodos de processamento. Os materiais orgânicos são facilmente processados em solução, portanto permite o uso de diversas técnicas de deposição, como por exemplo, as técnicas de impressão. Dentre as técnicas de impressão, a jato de tinta é a que mostra ser mais adequada à impressão de circuitos. Ela permite depositar volumes de soluções (ou suspensões) da ordem de picolitros em cada gota mantendo padrões bem definidos. Além disso, elimina o uso de máscaras, ocasionando diminuição nos custos e desperdício de material e, por ser um método de deposição tipo não-contato, minimiza possíveis contaminações. Esta tese dedicou-se, dentro desse contexto, ao domínio da técnica de jato de tinta para a confecção de transistores de efeito de campo orgânico (OFETs) tipo p e tipo n, e com aplicação em um inversor lógico unipolar. Os OFETs impressos usaram a arquitetura top gate/bottom contact (TG/BC. Os filmes semicondutores foram formados por várias linhas impressas sobre a região dos eletrodos fonte e dreno. Para os OFETs tipo p foi utilizado o semicondutor Poli(3-hexiltiofeno) régio-regular (rr-P3HT). Foram fabricados OFETs tipo p com a impressão de linhas utilizando os quatro diferentes padrões de deposição da impressora Autodrop. OFETs tipo p com mobilidade em torno de 3x10-3 cm2/V.s e razões Ion/Ioff da ordem de 103 foram obtidos utilizando um padrão de deposição paralelo e outro perpendicular a fonte e dreno. Para os OFETs tipo n o semicondutor usado foi o Poli{[N,N\'-bis(2-octildodecil)-naftaleno-1,4,5,8-bis(dicarboximida)-2,6-diil]-alt-5,5\'-(2,2\'-bitiofeno)]} (P(NDI2OD-T2)). Dentre os OFETs tipo n impressos os melhores apresentaram mobilidades em torno de 10-2 cm2/V.s e razões Ion/Ioff de aproximadamente 5x102. Ambos os OFETs impressos foram aplicados em inversores lógicos digitais unipolares com ganhos maiores que 1. / The technology of inorganic semiconductors has dominated the industry of electronics for many years. However, since the discovery of conductive polymers considerable effort has been devoted to studies and technological applications of these materials in electronic devices, starting a new branch of electronics: Organic Electronics (OE). One of the great advantages of OE lies in the processing methods. The organic materials are easily handled in solution, thus allows the use of various deposition techniques, as for example the printing techniques. Among the techniques of printing, inkjet is showing to be more suitable for printing circuits. It allows you to deposit solutions (or suspensions) volumes on the order of picoliters in each drop, performing well-defined patterns. Furthermore, it eliminates the use of masks, resulting in reduced costs and material waste. This thesis is dedicated to the field of inkjet technique, specifically for the fabrication of organic field-effect transistors (OFETs), p-type and n-type, and application in a unipolar logic inverter. Printed OFETs used architecture top gate/bottom contact (TG/BC). The semiconductor films were formed by several printed lines on the region of the source and drain electrodes. For p-type OFETs we used poly (3-hexylthiophene ) regio-regular (rr-P3HT) as semiconducting material. The p-type OFETs were fabricated using the four different patterns of deposition of the printer Autodrop. These OFETs showed mobility around 3x10-3 cm2/V.s and Ion/Ioff ratio of the order of 103 for the deposition pattern parallel and perpendicular to source and drain. For the n-type OFETs the semiconductor used was Poly{[N,N\'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5\'-(2,2\'-bithiophene)]} (P(NDI2OD-T2)). Among the printed n-type OFETs the best showed mobility around of 10-2 cm2/V.s and Ion/Ioff ratio of the order of 5x102. Both printed OFETs were applied in unipolar digital logic inverters, with gains greater than 1.

A importância da pesquisa em eletrônica orgânica, se comparada à microeletrônica convencional baseada principalmente em silício, surge pela presença de inúmeros semicondutores e técnicas de deposição de baixo custo e em grande superfície. Os Transistores de Filmes Finos Orgânicos (OTFTs, do inglês Organic Thin-Film Transistors) são a unidade fundamental em circuitos eletrônicos e, geralmente, apresentam a estrutura de um transistor de efeito de campo. Podem ser fabricados sobre substratos plásticos e oferecem grande número de aplicações como: mostradores, etiquetas de identificação por rádio frequência e eletrônica têxtil. Além disso, há demanda por componentes eletrônicos portáteis e baratos, principalmente como sensores em diagnósticos médicos e veterinários in-situ. A geometria de OTFT mais utilizada em sensores na atualidade é a bottom gate sobre substratos de silício altamente dopado e com óxido de porta inorgânico. Polímeros como poli(3-hexiltiofeno) (P3HT) vêm sendo amplamente utilizados pela comunidade científica, atestando o potencial comercial deste semicondutor em sensores. Neste contexto, esta tese apresenta o desenvolvimento de transistores à base de P3HT como sensores na detecção de analitos em fase vapor. O estudo é composto por uma etapa inicial de caracterização da mobilidade dos portadores de carga por técnicas de transiente de corrente, seguida pela otimização do desempenho de parâmetros elétricos do transistor através de alterações no processamento dos filmes dielétrico e semicondutor. Enfim, conclui-se a investigação através do entendimento dos fatores ligados à degradação do OTFT após exposição à atmosfera e sob estresse elétrico, além do detalhamento da sensibilidade e especificidade do sensor. Sensores de P3HT oferecem enorme potencial de detecção de amônia, cetonas e compostos organoclorados. Outros semicondutores poliméricos são provavelmente necessários para maior especificidade em relação a vapor dágua e álcoois. / Research on organic electronics, compared to conventional silicon-based microelectronics, is necessary as it offers plenty of semiconductors and low-cost deposition techniques that can be performed over wide surfaces. Organic Thin-Film Transistors (OTFTs) are the fundamental unity in electronic circuits and, usually, display the metal insulator semiconductor field-effect transistor (MISFET) structure. OTFTs can be processed over cheap plastic substrates and integrate a high number of applications as: flexible displays, radio frequency identification tags, textile electronics and sensors (e.g. chemical and biological compounds). Nowadays, consumers demand portable and low-cost electronic devices, mainly as sensors for in-situ medical and veterinarian diagnosis. The most widely used OTFT structure in sensing is the bottom-gate/bottom-contact FET over highly-doped silicon substrates and inorganic dielectrics. Polymers as poly(3-hexylthiophene) (P3HT) have found increasing acceptance by the scientific community, attesting their potential as semiconductors for commercial applications. In this context, the thesis lies in the development of organic transistors based in P3HT polymer for the detection of vapor-phase compounds. This study begins with transistor performance optimization through changes in dielectric and semiconductor processing. Thin-film thickness and P3HT cast solution drying time are the main studied parameters. It involves also the understanding of device performance degradation when exposed to atmosphere and under bias stress, before finally mapping sensitivity and specificity against gaseous analytes. P3HT-based sensors are potentially interesting for ammonia, ketones and organochlorides detection. Other polymeric semiconductors may be necessary to increase specificity against water steam and alcohol analytes.

Das Hauptaugenmerk dieser Arbeit liegt auf der Entwicklung einer Hybridsolarzelle, in der der anorganische Halbleiter Silizium, das organische Polymer und das Kontaktsystem so aufeinander abgestimmt sind, dass ihre Kombination zu einem Bauelement mit hohem Wirkungsgrad führt. Um dieses Ziel zu erreichen wurden verschiedene Maßnahmen ergriffen. Neue Polymermaterialien, abgeleitet von dem prototypischen organischen Halbleiter poly(3-hexylthiophen 2,5 diyl) (P3HT), namentlich poly(3-[3,6-dioxaheptyl]-thiophen) (P3DOT) und poly(3-[2,5,8-trioxanonyl]-thiophen) (P3TOT), wurden umfassend hinsichtlich ihrer Struktur untersucht. Poly thiophen/c-Si hybride Solarzellen, hergestellt aus diesen neuen Polymeren, erreichten Effizienzen bis zu 11 %. Die vollständigen Banddiagramme dieser Poly thiophen/c-Si Hybridgrenzflächen wurden mittels Photoelektronenspektroskopie aufgenommen. Außerdem wurde der Einfluss des Kontaktsystems auf die darunter liegenden Schichten mittels Oberflächenspannungsspektroskopie untersucht. Das Resultat dieser Messungen weißt eine Inversionslage unter der Siliziumoberfläche nach, die sich aufgrund des verwendeten semitransparenten Metallkontaktes formt. Dadurch lassen sich diese Bauteile als MIS Inversionsschicht Solarzelle kategorisieren. Um die Hybridsolarzellen weiter zu verbessern, wurde versucht den semitransparenten Metallkontakt durch Graphen zu ersetzen. Das Graphen wurde durch einen CVD-Prozess gewachsen und erreichte eine laterale Ausdehnung von bis zu 1 cm2. Der Übertrag auf die Solarzelle erfolgte mittels eines Wasser und Zerstörungsfreiem Transferprozess. Trotz dem erfolgreichen Aufbringen des Graphen limitierte ein geringer Füllfaktor aufgrund der geringen Ladungsträgerdichte im Graphen den Wirkungsgrad der Solarzelle. In einem letzten Schritt wurde das Polymer P3HT zum ersten Mal mit polykristallinen Siliziumabsorbern kombiniert. Die invertierte Zellstruktur, die hierbei zu Anwendung kam, erhöhte die Lebensdauer der Solarzelle erheblich. / The scope of this thesis was the development of a hybrid solar cell based on silicon in which the inorganic semiconductor, the organic polymer and the contact system are combined in such a manner to result in a photovoltaic device with high power conversion efficiency. To reach this goal several measures were taken. New polymer materials derived from the prototypical organic semiconductor poly(3-hexylthiophene 2,5 diyl) (P3HT), namely poly(3-[3,6-dioxaheptyl]-thiophene) (P3DOT) and poly(3-[2,5,8-trioxanonyl]-thiophene) (P3TOT), were extensively characterized regarding its structural properties. Poly thiophene/c-Si hybrid solar cells fabricated from these new polymers exhibited power conversion efficiencies up to 11 %. The energy level alignment of these poly thiophene/c Si hybrid interfaces was studied using photoelectron spectroscopy. Furthermore, the influence of the contact system on the underlying wafer is investigated with surface photovoltage measurements. The measurements revealed the formation of an inversion layer beneath the silicon surface due to the semitransparent metal contact used in the devices. Therefore, these devices can be classified as MIS inversion layer solar cells. To further improve the hybrid poly thiophene/c-Si solar cells by substituting the semitransparent metal contact, graphene was implemented in the device design as a transparent front contact. The CVD grown graphene sheet had a lateral size of up to 1 cm2 and was applied onto the solar cell using a non-destructive and water-free transfer process. However, despite the successful transfer the power conversion efficiency was restricted by the low fill factor due to a low charge carrier density in the graphene. As a last step, hybrid solar cells in the combination P3HT/polycrystalline silicon absorbers on glass were fabricated for the first time. The inverted device structure used for these solar cells proved beneficial for the lifetime. These devices were stable for up to 3 months.

Le but de cette thèse est d'étudier l'effet de l’alignement et le contrôle de la morphologie de films minces de polythiophènes et de les corréler avec les propriétés optiques, de transport de charges et thermoélectriques. Puisque les polymères semiconducteurs sont intrinsèquement anisotropes, il est essentiel de les aligner afin de comprendre leur propriétés. Cette étude a été réalisée en employant deux techniques qui ont permises d’obtenir des films minces orientés. Le brossage à haute température et la cristallisation épitaxiale directionnelle (CED) ont conduit à des films de polythiophène hautement orientés avec des paramètres d'ordre allant jusqu'à 0.87 et des taux de crystallinité jusqu'à 65%. La technique de brossage nous a permis de contrôler avec précision les tailles des domaines cristallins dans des films de P3HT brossés. Par cette méthode, nous avons pu également déterminer les températures de fusion à l'équilibre de différents poly(3-alkyl-thiophène). Nous avons appris que la largeur de bande du couplage excitonique W dépend des dimensions des cristaux dans les films minces brossés. Cette étude à aussi montrer l’importance de la planarité des chaînes pontant les domaines cristallins à travers les zones amorphes sur les propriétés de transport de charges. Nous avons également mis en évidence la morphologie particulière du poly (3-butylthiophène) (P3BT) et le rôle des groupements butyles. La méthode de cristallisation epitaxialle a été utilisée pour orienter des films de poly(3-dioctylphenyl-thiophène) (PDOPT). Nous avons examiné l'effet de la masse moléculaire du PDOPT sur le degré de cristallinité et l'alignement. Ceci nous a permis de proposer un modèle structural montrant l’absence de pi-stacking dans ce polythiophène. Finalement, nous proposons une méthode en deux étapes d’élaboration de films minces conducteurs alignés. Le brossage des films puis le dopage des polymères semiconducteurs de type-P a permis d’obtenir des propriétés thermoélectriques anisotropes améliorées.Cette thèse démontre l'importance du contrôle de la morphologie et de l'alignement des polymères semiconducteurs et conducteurs pour comprendre leurs propriétés fortement anisotropes. / The aim of this thesis is to study the effect of alignment and morphological control on polythiophene thin films and to correlate this control with the optical, charge transport and thermoelectric properties. Since semiconducting polymers are inherently anisotropic by nature, studying these polymers in the aligned state was essential to understand their properties. This study could be achieved by employing two techniques that are successful in orienting polymers in thin films. High-temperature rubbing (HTR) along with directional epitaxial crystallization (DEC) produced highly oriented polythiophene thin films with order parameters reaching 0.87 and crystallinities up to 65%. HTR was a successful method to control crystal sizes in rubbed poly(3-hexyl-thiophene) P3HT films. By this method, the equilibrium melting temperatures of other poly(3-alkyl-thiophene) P3ATs were calculated. We learned that the free excitonic bandwidth depends on the crystal dimensions in the rubbed thin films. We also learned that the planarity of tie-chains linking consecutive crystalline domains plays a very important role in field-effect mobility. We also discuss the peculiar morphology of poly(3-butyl-thiophene) (P3BT) and the role of the butyl side groups. Then DEC method was proposed to orient poly(3-dioctylphenyl-thiophene) (PDOPT) thin films. We examined the effect of molecular weight of PDOPT on the level of crystallinity and alignment. Consequently, this relation provided fundamental information that helped us refine the crystal structure of PDOPT. Finally, a versatile method to produce highly aligned conducting polymers was proposed. HTR followed by P-type doping proved to be an excellent way to produce highly aligned conducting thin films with enhanced thermoelectric properties. This thesis brings value to the importance of morphology control and the alignment of semiconducting thin films to understand the various properties of these highly anisotropic systems.

Ce travail a été consacré à la caractérisation, l’optimisation et l’étude du comportement photochimique de couches actives de cellules photovoltaïques organiques. L’objectif était d’identifier les mécanismes de photovieillissement dans le but de proposer des stratégies pour améliorer la stabilité de cellules solaires organiques à base de Poly(3-hexylthiophène) (P3HT) et de [6,6]-phényl-C61-butanoate de méthyl (PCBM). Le premier axe de travail a été consacré à l’étude de l’influence des paramètres structuraux du P3HT (masse molaire, régiorégularité, pureté …) sur sa stabilité photochimique dans un premier temps, puis sur l’optimisation des performances des cellules dans un second temps. Pour ce faire, quatre P3HT commerciaux différents ont été étudiés. Ils ont tout d’abord été caractérisés avec précision grâce à différentes techniques analytiques. La relation entre microstructure du P3HT et sa photostabilité a ensuite été étudiée, et les paramètres pertinents influençant la photodégradation identifiés. Le deuxième axe de travail a été consacré à la stabilité photochimique de mélanges P3HT:PCBM sur substrat inerte, puis sur des couches tampons. Dans une dernière partie, la dégradation de couches actives au sein de dispositifs complets a été effectuée en faisant « l’autopsie » de cellules vieillies. / This work was devoted to optimization, characterization and photochemical behavior of active layers of organic solar cells. The objective was to identify photo-ageing mechanisms in order to propose strategies to improve the stability of Poly (3-hexylthiophene) (P3HT)/[6,6]-phenyl-C61-butanoic acid methyl ester (PCBM) organic solar cells. The first axe of this work was devoted to the study of the influence of structural parameters of P3HT (molecular weight, regioregularity, purity …) firstly on its photochemical stability and secondly on the optimization of the performances of devices. In this goal, four different commercial P3HT were studied. They were first characterized accurately with different analytical techniques. The relationship between P3HT microstructure and photostability has been studied and relevant parameters influencing photodegradation have been identified. The second axe of this work was devoted to the photochemical stability of P3HT:PCBM blends on inert substrate, and then on buffer layers. Finally, the degradation of active layers in complete devices has been performed by making the “autopsy” of degraded solar cells.

A eletrônica digital desempenha papel essencial no desenvolvimento e manutenção dos padrões de vida em prática hoje no mundo. A peça fundamental para a criação desta era tecnológica é sem dúvidas o transistor. Com o advento de novos materiais, a busca por transistores que oferecem novas oportunidades de processamento e aplicação permitiu que uma nova área fosse criada: a eletrônica orgânica. Transistores de efeito de campo baseados em filmes finos de materiais orgânicos têm recebido grande atenção nas últimas décadas. Apresentamos um estudo experimental e teórico de transistores de efeito de campo a base de filmes finos orgânicos. Foram caracterizados transistores usando um derivado do pentaceno (TMTES-pentaceno) como camada ativa em um dispositivo feito sobre Si/SiO2. Mostramos que a inclusão do semicondutor orgânico em uma matriz polimérica isolante ajuda a manter a estabilidade termo mecânica do dispositivo. Foi desenvolvido um modelo que levasse em conta as resistências parasíticas para explicar o comportamento do transistor em função da temperatura. Também foram construídos e caracterizados transistores usando rr-P3HT como semicondutor e PMMA como isolantes. Apresentamos transistores do tipo Top-Gate e Bottom-Gate com mobilidade máxima de 7 x 10-3 cm2/V.s. Valores de razão ON/OFF de ~ 900 foram encontrados nos transistores otimizados. O comportamento dos transistores é analisado em função da temperatura e os modelos de aproximação de canal gradual e de Vissenberg-Matters foram aplicados para extração dos parâmetros de interesse. Por fim, apresentamos um modelo de corrente de canal baseado na resolução 2D numérica da equação de Poisson usando as idéias de Vissenberg-Matters para a concentração de cargas em função do potencial local. O modelo, embora ainda nos primeiros estágios de desenvolvimento, prevê a saturação da corrente nas curvas de saída simuladas sem limitações de regime de validade. / Digital electronics plays an essential role in the development and maintenance of living standards into practice in the world today. The cornerstone for the creation of this technological age is undoubtedly the transistor. With the advent of new materials, the search for transistors that offer new opportunities in processing and application allowed a new area to be created: the organic electronics. Field effect transistors based on organic thin films have received great attention in recent decades. We report an experimental and theoretical study of field effect transistors based on organic thin films. We characterized transistors manufactured using a derivative of pentacene (TMTES-pentacene) as the active layer in a device and using Si/SiO2 as gate and insulator. We show that the inclusion of the organic semiconductor in an insulating polymeric matrix helps to maintain the termo-mechanical stability of the device. A model was developed that take into account the parasitic resistances and to explain the behavior of the transistor as a function of temperature. We also present the manufacturing and characterization process of transistors using rr-P3HT as semiconductor and PMMA as insulator. We report Top-Gate and Bottom-Gate transistors with maximum mobility of 7 x 10-3 cm2/V.s. The maximun ON/OFF ratio of ~ 900 was found for the optimized transistors. The behavior of the transistors was analyzed as a function of temperature and both gradual channel approximation and Vissenberg-Matters models were applied for extracting the parameters. Finally, we present a channel current model based on the resolution of 2D numerical Poisson equation using the ideas of Vissenberg-Matters to the calculate the concentration of charges due to the local potential. The model, although still in the early stages of development, predicts the saturation current at output simulated curves with no limitation of regime validity.

A tecnologia dos semicondutores inorgânicos tem dominado a indústria eletrônica por muitos anos. No entanto, com a descoberta dos polímeros condutores um esforço considerável tem sido dedicado ao estudo e às aplicações tecnológicas desses materiais em dispositivos eletrônicos, dando início a um novo ramo da eletrônica: a Eletrônica Orgânica (EO). Uma das grandes vantagens da EO reside nos métodos de processamento. Os materiais orgânicos são facilmente processados em solução, portanto permite o uso de diversas técnicas de deposição, como por exemplo, as técnicas de impressão. Dentre as técnicas de impressão, a jato de tinta é a que mostra ser mais adequada à impressão de circuitos. Ela permite depositar volumes de soluções (ou suspensões) da ordem de picolitros em cada gota mantendo padrões bem definidos. Além disso, elimina o uso de máscaras, ocasionando diminuição nos custos e desperdício de material e, por ser um método de deposição tipo não-contato, minimiza possíveis contaminações. Esta tese dedicou-se, dentro desse contexto, ao domínio da técnica de jato de tinta para a confecção de transistores de efeito de campo orgânico (OFETs) tipo p e tipo n, e com aplicação em um inversor lógico unipolar. Os OFETs impressos usaram a arquitetura top gate/bottom contact (TG/BC. Os filmes semicondutores foram formados por várias linhas impressas sobre a região dos eletrodos fonte e dreno. Para os OFETs tipo p foi utilizado o semicondutor Poli(3-hexiltiofeno) régio-regular (rr-P3HT). Foram fabricados OFETs tipo p com a impressão de linhas utilizando os quatro diferentes padrões de deposição da impressora Autodrop. OFETs tipo p com mobilidade em torno de 3x10-3 cm2/V.s e razões Ion/Ioff da ordem de 103 foram obtidos utilizando um padrão de deposição paralelo e outro perpendicular a fonte e dreno. Para os OFETs tipo n o semicondutor usado foi o Poli{[N,N\'-bis(2-octildodecil)-naftaleno-1,4,5,8-bis(dicarboximida)-2,6-diil]-alt-5,5\'-(2,2\'-bitiofeno)]} (P(NDI2OD-T2)). Dentre os OFETs tipo n impressos os melhores apresentaram mobilidades em torno de 10-2 cm2/V.s e razões Ion/Ioff de aproximadamente 5x102. Ambos os OFETs impressos foram aplicados em inversores lógicos digitais unipolares com ganhos maiores que 1. / The technology of inorganic semiconductors has dominated the industry of electronics for many years. However, since the discovery of conductive polymers considerable effort has been devoted to studies and technological applications of these materials in electronic devices, starting a new branch of electronics: Organic Electronics (OE). One of the great advantages of OE lies in the processing methods. The organic materials are easily handled in solution, thus allows the use of various deposition techniques, as for example the printing techniques. Among the techniques of printing, inkjet is showing to be more suitable for printing circuits. It allows you to deposit solutions (or suspensions) volumes on the order of picoliters in each drop, performing well-defined patterns. Furthermore, it eliminates the use of masks, resulting in reduced costs and material waste. This thesis is dedicated to the field of inkjet technique, specifically for the fabrication of organic field-effect transistors (OFETs), p-type and n-type, and application in a unipolar logic inverter. Printed OFETs used architecture top gate/bottom contact (TG/BC). The semiconductor films were formed by several printed lines on the region of the source and drain electrodes. For p-type OFETs we used poly (3-hexylthiophene ) regio-regular (rr-P3HT) as semiconducting material. The p-type OFETs were fabricated using the four different patterns of deposition of the printer Autodrop. These OFETs showed mobility around 3x10-3 cm2/V.s and Ion/Ioff ratio of the order of 103 for the deposition pattern parallel and perpendicular to source and drain. For the n-type OFETs the semiconductor used was Poly{[N,N\'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5\'-(2,2\'-bithiophene)]} (P(NDI2OD-T2)). Among the printed n-type OFETs the best showed mobility around of 10-2 cm2/V.s and Ion/Ioff ratio of the order of 5x102. Both printed OFETs were applied in unipolar digital logic inverters, with gains greater than 1.