Self-assembled monolayers and surface-initiated polymer, or polymer brushes, have attracted attention as they form dense layers with much higher structural order than bulk or solution polymers. Another field of research which has emerged over the last two decades is the field of organic and polymer electronics. In this field molecular order and surface modification are of major influence on the device performance, hence that both self-assembled monolayers as polymer brushes have been investigated to find applications in organic electronic devices. After an introduction into the field self-assembled monolayers, polymer brushes and organic electronics, the first part of this thesis focusses on three applications of surface modification techniques for applications in devices. Alignment of the active material is crucial for high mobilities in organic electronics. Chapter 2 discusses the synthesis of a liquid crystalline surface-initiated polymer and its application to induce strong homeotropic alignment. The alignment is homogeneous over large areas and can be patterned by combining the polymerization with soft lithographic techniques. Mobilities of organic electronic materials can also be strongly influenced by dopants in the material. In field-effect transistors the positioning of the dopant is thought to be crucial, as the conductance predominantly takes place in only a small channel near the dielectric interface. In chapter 3 dopant functionalized monolayers and polymer brushes are presented which enable the localized deposition of dopants in the channel of organic transistors. It is shown that the mobility of charges and hence the device performance is affected by the introduction of this dopant layer. Polymer brushes have been suggested for the fabrication of highly ordered semiconducting polymers. In chapter 4 the use of a thiophene functionalized polymer brush is shown, that can be used as a template for the subsequent growth of highly conjugated surface grafted polythiophene layers. Thick polythiophene layers are obtained, that are low in roughness and show photoluminescence and polychromism upon doping. The second part (chapter 5 and 6) of this thesis presents new techniques for surface polymerizations. It is attractive to investigate reduction of reactor volume for polymer brush growth. Chapter 5 discusses a method to achieve volume reduction by back-filling the superfluous volume with beads. It is found that this influences the polymerization kinetics significantly. The combined advantages of less volume and enhanced reaction speeds enable reduction of the total amount of monomer needed by up to 90%. Chapter 6 presents a controlled way to convert initiators for atom transfer radical polymerization into initiators for nitroxide mediated polymerization. In this way mixed polymer brushes and block co-polymer brushes become accessible. This combination makes it an attractive tool to fabricate complex polymer architectures. The technologies used in this thesis show that the synthesis of polymer brushes enable the fabrication of complex architectures without the wastes normally associated with surface-initiated polymers. Combined with several functionalized polymer brushes with properties that enhance order, influence mobility or serve as template for the growth of surface attached conjugated polymers this shows the high potential for the application of surface-initiated polymers in organic electronics.

La thèse porte sur les mesures de courants transitoires limités par la charge d'espace dans des films minces organiques (épaisseur < 500 nm). Ce type de films est souvent utilisé dans des applications dans le domaine de l'électronique organique comme couches actives semi-conductrices. Le transport électrique dans ces films dépend en premier lieu du transport des porteurs de charge dans le milieu massif et de leur piégeage, mais aussi de l'efficacité de l'injection des porteurs de charges à partir des électrodes métalliques. L'ensemble est de plus conditionné par le taux de désordre inhérent aux matériaux organiques. L'approche qui consiste à utiliser la mesure de courants transitoires est extrêmement attractive car elle permet en principe de fournir une information sur tous ces aspects à l'issue d'un seul type de mesure. Dans ce cadre, trois contributions principales peuvent être dégagées de la thèse. 1) Tout d'abord, nous avons validé un montage expérimental qui utilise un amplificateur à transfert d'impédance pour la mesure des courants transitoires limités par la charge d'espace. Ce type de montage s'avère supérieur au circuit de pont électrique le plus largement utilisé jusqu'à maintenant car il présente une meilleure sensibilité en courant, une meilleure bande passante, et ne nécessite aucun réglage ni de la symétrie du pont ni de l'ajustement de la taille de l'échantillon. On a pu démontrer que le pic de courant de déplacement initial, qui sature l'amplificateur au tout début de la mesure n'introduit pas d'erreur dans la mesure de la mobilité. 2) Ensuite concernant l'étude plus spécifique du transport dans un dendrimère à base de tri-arylamine, les réponse en courant obtenues expérimentalement se sont avérées en bon accord avec le modèle de déplacement-diffusion. Cependant, la troisième leçon que nous avons apprise est que l'obtention d'un tel accord a nécessité que soient très bien définies les conditions initiales tant de l'expérience que de la simulation et qu'un modèle théorique le plus complet possible de l'échantillon soit considéré. Pour le dendrimère ce modèle a dû prendre en compte l'effet de la barrière au contact et les effets de piégeage. Un accord encore meilleur a été obtenu en intégrant de surcroit les effets de désordre. 3) La complète impossibilité d'obtenir un bon accord sans un modèle physique complet de l'échantillon indique que les paramètres liés au piégeage, à la barrière au contact et à la mobilité peuvent véritablement être ajustés sans aucune ambigüité. Ainsi, une caractérisation électrique complète en cohérence avec la simulation a pu être obtenue à l'issue d'un seul type de mesures. Les résultats obtenus, alliant à la fois amélioration technique et support numérique, témoignent de la grande utilité de cette technique de mesure de courant transitoire limité par la charge d'espace pour caractériser en détails le transport dans les films minces organiques. / The thesis concerns space-charge-limited transient current measurements in thin (le500 nm) organic films. Such films find important applications in organic electronics, where they are referred to as organic semiconductor layers. Electrical transport in such films depends on bulk charge carrier transport and trapping, as well efficiency of charge carrier injection from electrodes. These, are all in turn depend on disorder inherent to organic materials. The transient measurement approach is very attractive, as it can, in principle, deliver information on all these aspects in one single measurement. In the thesis, three main contributions are presented. 1) A transimpedance amplifier based setup for space-charge-limited current transient measurement is validated. This type of setup is superior to the widely used bridge circuit, notably because of better current sensitivity, bandwidth, no need for bridge symmetry and no need for per sample adjustment. It is demonstrated that initial displacement current spike, which saturates the amplifier at the beginning of measurement, does not introduce error in the measurement of mobility. 2) A dendrimer molecule has been investigated. Experimental current responses are shown to be in agreement with the drift-diffusion model. However, obtaining agreement requires well defined initial conditions in experiment as well as in simulation, and also complete theoretical model of the sample. In the case of dendrimer, this model had to take into account both contact barrier and trapping effects. Furthermore, better agreement was obtained when taking disorder effects into account. 3) The impossibility of obtaining any agreement without complete physical model of the sample indicates that trapping, contact barrier and mobility parameters could be fitted without ambiguity. Therefore, complete electrical characterization consistent with simulation can be obtained using the transient technique. The results obtained further increase well known usefulness of transient space-charge-limited current characterization of thin organic films.

Les matériaux à propriétés thermoélectriques sont utilisés pour des applications de récupération d'énergie thermique, de génération de froid ou encore de détection de flux de chaleur. L'efficacité de ces matériaux, caractérisée par les facteurs de mérite et de puissance thermoélectriques, est optimale lorsque le coefficient Seebeck, la conductivité électrique, et la résistivité thermique sont élevés. Aux températures ambiantes, les meilleurs rendements sont atteints pour des alliages basés sur le tellurure de bismuth Bi2Te3 dont le coût et la toxicité sont des verrous pour le développement d'applications à grande échelle. Dans l'optique du développement d'alternatives à ces matériaux, les polymères conjugués sont envisagés depuis quelques années. Leurs propriétés sont toutefois largement inférieures à celles du Bi2Te3.Cette thèse a pour objectif l'étude et l'amélioration des performances thermoélectriques de matériaux basés sur le poly(3,4-éthylènedioxythiophène) ou PEDOT. Elle s'organise principalement autour de trois axes de travail. La première partie présente l'étude de propriétés thermoélectriques de formulations commerciales de PEDOT. L'influence de divers paramètres (l'ajout d'inclusions, l'utilisation d'un dopant secondaire, la modification de son taux d'oxydation…) sur les propriétés thermoélectriques est mesurée. Notamment, l'efficacité du dopage secondaire pour améliorer le facteur de puissance du matériau, ainsi que la relation entre le taux d'oxydation et le coefficient Seebeck du matériau, sont mis en évidence.Dans un second temps, le PEDOT est synthétisé avec des contre-ions à faible encombrement stérique et peu coordinants. Les propriétés thermoélectriques des matériaux obtenus sont supérieures à celles offertes par les formulations commerciales. La forte dépendance entre le transport de charge et la structure du matériau est mise en évidence. De plus, une méthode de dopage primaire du matériau permettant une forte augmentation de la conductivité électrique a été étudiée.Enfin, des pistes de réflexion pour l'intégration des matériaux développés dans cette thèse ont été explorées. Dans ce cadre, des méthodes de mises en forme originales ont notamment été démontrées.Cette thèse a permis d'apporter des éléments de compréhension sur les relations entre les propriétés thermoélectriques des polymères conjugués, leur taux d'oxydation, la nature de leurs dopants, et leur structure. Les résultats obtenus laissent envisager plusieurs voies d'optimisation des propriétés des matériaux organiques qui devront faire l'objet de futurs travaux. / Thermoelectric materials are useful for applications such as heat waste recovery, cold production or heat flux detection. The factor of merit and the power factor of the materials characterize their efficiency. These factors are optimal for high Seebeck coefficient, electrical conductivity, and thermal resistivity. The higher yields for room-temperature applications are achieved with materials based on bismuth telluride alloys, but the cost and the toxicity of these materials prevent the development of large-scale applications. In recent years, conjugated polymers have been contemplated as alternatives for Bi2Te3, however, their thermoelectric properties are significantly lower.This thesis aims at studying and improving the thermoelectric performances of materials based on poly3,4-ethylene dioxythiophene) or PEDOT. It consists of three areas of work. In the first part the thermoelectric properties of commercial formulations of PEDOT is presented. The influence of various parameters (such as additional loads, secondary doping species or redox reactions) on the thermoelectric properties is studied. Notably, the propensity of secondary doping to improve the power factor of the material, and the relationship between the oxidation and the Seebeck coefficient of the material rate, are set evidences.In a second part of the work, PEDOT is synthetized with less sterically hindered, poorly coordinating counter-ions. Thermoelectric properties of the resulting materials are higher than those offered by commercial formulations and the strong dependence of the charge transport and the material structure are highlighted. Moreover, a method of doping the primary material allowing great increases of the electrical conductivity was also studied.Finally, several routes for the integration of the above mentioned materials in thermoelectric modules are explored. Original shaping methods have been demonstrated.This thesis provides understandings on the relationship between the thermoelectric properties, the oxidation rate and the structure of conjugated polymers. The results suggest that several ways can be considered in order to improve the thermoelectric efficiency of these materials. These routes will be the subject of future work.

O trabalho desta dissertação versou sobre avanços em tecnologias de eletrônica impressa de baixo custo. Em particular, aplicamos as técnicas de impressão por serigrafia e por jato de tinta para confeccionar dispositivos eletrônicos e optoeletrônicos. O primeiro dispositivo construído foi resistências impressas por jato de tinta tendo como matérias primas o poli(3,4-etileno dióxido tiofeno) com sulfonato de poliestireno (PEDOT:PSS) e nanopartículas de prata sobre substratos de vidro. Os valores das resistências foram analisados em se variando parâmetros de impressão. Como segundo dispositivo, imprimimos pela técnica de serigrafia sobre vidro e kapton, antenas de cartões de RFIDs (Radio-Frequency Identifications), também com os dois materiais: tinta de prata e PEDOT:PSS. Os RFIDs foram projetados para operar em frequências entre 860 MHz e 960 MHz. A antena de PEDOT:PSS mostrou alcance de 0,45 m, enquanto que a de tinta prata teve alcance de 1,6 m em 860 MHz e de 4 m em 960 MHz. Fabricamos também células eletroquímicas emissoras de luz (Organic Light Emitting Electrochemical Cells - OLECs), no qual substituímos o eletrodo transparente de óxido de índio (ITO), por um feito de PEDOT:PSS, aplicado por serigrafia sobre vidro. A camada ativa da célula luminescente foi feita por uma mistura de óxido de polietileno complexado com sal de lítio e um polímero luminescente derivado de polifluoreno que emite no verde. As curvas características de corrente e luminância em função da voltagem externa aplicada mostrou o bom desempenho das células fabricadas. Finalmente, produzimos células fotovoltaicas orgânicas, em que o eletrodo transparente, também de PEDOT:PSS, foi depositado por serigrafia sobre vidro. A camada ativa nesse caso foi um sistema bifásico feito de poli(3hexiltiofeno) (P3HT) e um éster, o [6,6]-fenil-C61-ácido metil-butírico (PCBM). Esse dispositivo apresentou um Fator de Preenchimento de 0,47 e uma eficiência externa de aproximadamente 2%. / The work developed along this thesis presents advances in printed electronic technologies of low cost. In particular we applied printable serigraphic and Inkjet technologies to produce electronic and optoelectronic devices. First, we produced resistances having poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) and silver paint as active materials, using an Inkjet printer on glass substrate. We made studies of the resistance performance varying some printed parameters. Then, by serigraphy screen printing was printed, on substrates of kapton and glass, an antenna in an Radio-Frequency Identification card (RFID), also from PEDOT:PSS and from silver paint. This RFID was projected to operate in a frequency range from approximately 860 MHz to 960 MHz. The antenna made of PEDOT:PSS operated in a distance of 0.45 m, while that of silver varied from 1.6 m at 860 MHz to 4 m at 960 MHz. In an Organic Light Emitting Electrochemical Cell (OLEC) we applied one of the electrodes, a PEDOT:PSS layer, as a transparent electrode by serigraphy on glass substrate for made to replace of ITO. The active layer was a mixture of a poly(ethylene oxide) complexed with lithium salt and a derivative of polyfluorene that is a green emitter. The characteristic curves of current and luminance against the applied external voltage assured us the good performance of the device. Similar result was obtained with the performance of an organic photovoltaic (OPV), in which the active layer was a biphasic system made by poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), in which the transparent electrode (PEDOT:PSS) was also printed by serigraphy on glass substrate. In this device we obtained a Fill Factor of 0.47 and an external efficiency of almost 2%.

Submitted by Luíz Gustavo Simão Albano (luizgustavoalbano@gmail.com) on 2018-04-20T20:51:26Z No. of bitstreams: 1 TESE_ALBANO_LGS-23-02-2018.pdf: 13982901 bytes, checksum: 09610d28485aca4fecdd9833a5f43b00 (MD5) / Approved for entry into archive by Maria Marlene Zaniboni null (zaniboni@bauru.unesp.br) on 2018-04-23T19:56:14Z (GMT) No. of bitstreams: 1 albano_lgs_dr_bauru.pdf: 13982901 bytes, checksum: 09610d28485aca4fecdd9833a5f43b00 (MD5) / Made available in DSpace on 2018-04-23T19:56:14Z (GMT). No. of bitstreams: 1 albano_lgs_dr_bauru.pdf: 13982901 bytes, checksum: 09610d28485aca4fecdd9833a5f43b00 (MD5) Previous issue date: 2018-02-23 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Atualmente, a eletrônica baseada em materiais orgânicos vem ganhando visibilidade no cenário científico e tecnológico devido à alta flexibilidade mecânica e baixo custo desses materiais. A fabricação de dispositivos eletrônicos baseados em materiais orgânicos e técnicas de baixo custo é um desafio pertinente e atual. Os transistores merecem destaque por serem a base da tecnologia atual. Em especial, uma arquitetura vertical comumente conhecida como VOFET (Transistor Orgânico de Efeito de Campo em Arquitetura Vertical) vem sendo explorada nos últimos anos. Entretanto, um problema comum em VOFETs é o eletrodo intermediário, o qual deve ser permeável a campos elétricos e apresentar baixa resistência de folha utilizando técnicas com baixo custo de produção. Desta forma, na primeira parte deste trabalho é apresentado o desenvolvimento de um eletrodo intermediário baseado em nanofios de prata utilizando a técnica de baixo custo conhecida como Mayer rod-coating. Os eletrodos otimizados foram aplicados em dispositivos VOFETs, resultando em transistores com densidades de corrente de 2,5 mA/cm2 e razão on/off de 5x103, utilizando tensões de operação de até 2 V. Além dos semicondutores orgânicos comumente sintetizados, corantes naturais também vêm sendo explorados para aplicações em dispositivos eletrônicos. Dentre eles, a melanina desperta atenção por ser um pigmento natural encontrado em vários sistemas biológicos. No corpo humano a melanina é responsável por funções como pigmentação, fotoproteção e termoregulação. Suas características de transporte em função da umidade associada à sua alta biocompatibilidade, tem originado considerável interesse para aplicações em dispositivos eletrônicos. Apesar de suas vantagens, quando extraída in vivo a melanina apresenta considerável irregularidade estrutural e pouca solubilidade, sendo necessário o desenvolvimento de rotas sintéticas para a obtenção de filmes finos de qualidade. Assim, na segunda parte deste trabalho, foi explorada a obtenção de filmes finos de melanina para aplicações na eletrônica orgânica. Os resultados obtidos permitiram à aplicação desse material em transistores eletroquímicos. Além disso, um estudo considerando diferentes condições de umidade relativa e pHs permitiu mostrar que sua condutividade é governada pela reação de comproporcionamento. Na terceira parte deste trabalho, foi estudada a fabricação de filmes finos utilizando diferentes porcentagens de melanina em matrizes de álcool polivinílico, para simultâneas aplicações como filtros protetores de radiação ultravioleta e capacitores orgânicos transparentes. Os filmes finos fabricados apresentaram excelente desempenho contra os raios UVA, bloqueando 100 % dos raios incidentes, além de funcionar de forma simultânea como capacitores orgânicos transparentes utilizando nanofios de prata como eletrodos. A integração dos filtros com a eletrônica orgânica permite futuras aplicações desse sistema em janelas ópticas inteligentes. Na última parte deste trabalho, foi estudada a reticulação de cadeias poliméricas do álcool polivinílico através inserção da melanina com intuito de substituir o dicromato de amônio, tradicionalmente utilizado na de reticulação do polímero. Os resultados obtidos mostraram que os filmes finos com 0,5 % de melanina apresentaram uma redução na densidade de corrente de quase duas ordens de magnitude em comparação com os filmes finos de álcool polivinílico, comportamento similar quando a reticulação é realizada com dicromato de amônio. Os resultados obtidos neste trabalho mostram a possibilidade de fabricar dispositivos eletrônicos baseados em materiais orgânicos e técnicas de baixo custo. O uso da melanina mostra ser uma alternativa interessante, pois além de sua alta biocompatibilidade, este material pode desempenhar diferentes funções em dispositivos eletrônicos. / Currently, electronics based on organic materials has been acquiring visibility in the scientific and technological scenario due to the high mechanical flexibility and low-cost of these materials. The fabrication of electronic devices based on organic materials and low-cost techniques is a relevant and current challenge. Transistors deserve attention because they are the base of our current technology. In particular, a vertical architecture commonly known as VOFET (Vertical Organic Field Effect Transistor) has been explored in recent years. However, a common issue in VOFET structure is the intermediate electrode, which must be permeable to electric fields with low sheet resistance using low-cost production techniques. Thus, in the first part of this work, the development of an intermediate electrode based on silver nanowires using the low-cost technique known as Mayer rod-coating is presented. The optimized electrodes were applied in VOFETs, resulting in devices with current densities of 2.5 mA/cm2 and on/off ratio of 5x103, using operating voltages up to 2 V. Apart from to the organic semiconductors commonly synthesized, natural dyes are also being explored in organic electronics. Among them, melanin deserves attention because it is a natural pigment found in several biological systems. In the human body melanin is responsible for functions such as pigmentation, photoprotection and thermoregulation. The humidity-dependent electrical response associated with the high biocompatibility has provided considerable interest for applications in electronic devices. However, melanin when extracted in vivo presents considerable structural irregularity and low solubility. In this way, the development of synthetic routes to obtain thin films with quality has been considered. Thus, in the second part of this work, the fabrication of melanin thin films was explored for applications in organic electronics. The results obtained allowed the application of melanin thin films in electrochemical transistors. In addition, a study considering different conditions of relative humidity allowed observe that its electronic conductivity is governed by the comproportionation reaction. In the third part of this work, the fabrication of poly(vinyl alcohol) thin films with different percentages of melanin were studied for simultaneously applications as ultraviolet filters and transparent organic capacitors. The thin films fabricated presented good performance against UVA radiation, blocking 100 % of the incident rays and working as transparent organic capacitors using silver nanowires as electrode. The integration of the filters with organic electronics allows future applications of this system in smart windows. In the last part of this work, the crosslinking of poly(vinyl alcohol) polymer chains through melanin incorporation was studied in order to replace ammonium dichromate. Ammonium dichromate is traditionally used in the poly(vinyl alcohol) crosslinking process. The results showed that the thin films with 0.5 % of melanin presented a reduction factor of almost 100 in current density when compared to the neat thin films, similar behavior when the crosslinking is performed with inorganic materials. The results obtained in this work showed the possibility to fabricate electronic devices based on organic materials and low-cost techniques. In addition, the use of melanin is an interesting alternative due to the fact that this material has high biocompatibility and can perform different functions in electronic devices. / FAPESP: 13/09963-6 / FAPESP: 13/07296-2 / FAPESP: 14/25332-9

Le but de cette thèse était d’auto-assembler des entités triarylamines donneurs d’électrons et capables de s’empiler en fibres conductrices sous l’action de la lumière, avec des entités accepteurs d’électrons de manière à obtenir des hétérojunctions supramoléculaires. Ces objectifs ont été atteints dans des versions dites statiques (distances constantes entre canauxdonneur et accepteur d’électrons) mais aussi dans une version dynamique ou la distance entre unités électroactives change grâce à l’action contrôlée d’un muscle moléculaire intégré. Ces systèmes auto-assemblés fonctionnels ont montré des changements très importants de leurs propriétés optoélectroniques en réponse à des stimuli orthogonaux comme la lumière et le pH. / The aim of this thesis was to self-assemble electron-donating triarylamine units, capable of aggregation into conducting fibers triggered by light, with electron-accepting entities to obtain supramolecular heterojunctions. These objectives were attained, that is in static versions (with constant distances between electron-donating and -accepting channels) and in a dynamicversion wherein the distance between the electroactive units changes owing to the controlled action of an integrated molecular muscle. These functional self-assembled systems showed very important changes in their optoelectronic properties in response to orthogonal stimuli such as light and pH.

Células eletroquímicas poliméricas emissoras de luz, PLECs, são dispositivos eletrônicos orgânicos que vêm despertando muito interesse comercial por operarem sob baixa tensão com alto desempenho e sem a necessidade de eletrodos específicos, como o óxido de estanho e índio (ITO), cálcio entre outros. Esta característica confere a possibilidade de processamento de baixo custo e de obter dispositivos flexíveis. Nas PLECs a injeção de portadores eletrônicos de carga nas interfaces, entre a camada ativa do dispositivo e seus eletrodos, é facilitada por ação de espécies iônicas, que são inseridas no material polimérico por adição de um sal. Do ponto de vista científico, o interesse atual reside na completa compreensão dos fenômenos de transporte de portadores eletrônicos no interior do dispositivo. Hoje existem dois modelos concorrentes. Um considera o transporte eletrônico por difusão e o outro leva em consideração a dopagem eletroquímica e a consequente formação de uma junção PIN (semicondutor dopado tipo-p camada isolante semicondutor dopado tipo-n). Nesse contexto, propusemos a fabricação e caracterização elétrica de PLECs com diversas composições e espessuras a fim de confrontar os resultados experimentais com os modelos em questão. Demonstramos a existência de uma concentração crítica de sal, abaixo da qual a operação da PLEC é promovida predominantemente por injeção auxiliada pela formação de duplas-camadas devido ao movimento iônico. No regime de tensões mais elevadas, além da injeção, ocorre a dopagem tipo-p e tipo-n e a formação da junção PIN. Além disso, determinamos que para tensões superiores à de operação o dispositivo apresenta comportamento ôhmico, com resistência elétrica proporcional à espessura do dispositivo e praticamente independente da temperatura. Nossos resultados mostraram que no regime de tensões mais baixas deve ocorrer um processo de transporte por difusão, mas à medida que a tensão aumenta, inicia-se um processo de dopagem tipo-p de um lado e tipo-n de outro, aumentando a condutividade das regiões dopadas e finalizando com a formação de uma junção PIN. Mostramos também que a tensão acumulada nas duplas-camadas independe do tipo de polímero eletrônico, e que a tensão de operação, aquela na qual o polímero luminesce, é semelhante á do gap da banda proibida do polímero luminescente. / Polymer light emitting electrochemical cells, PLECs, are organic electronic devices that have attracted commercial interest because they operate at low voltage and exhibit high performance without the need of specific electrodes such as indium tin oxide (ITO), calcium and others. This feature provides low cost of fabrication and exible devices. The charge injection in the PLECs is facilitated by the action of ionic species, which are inserted in the polymeric material by adding a salt. This thesis treats with a controversy related to transport phenomena along the bulk of the device. Currently, there is two opposite models. One that considers that transport is driven by diffusion mechanism; and the other takes into account the formation of a PIN junction (p-type semiconductor insulating layer n-type semiconductor). Here, we proposed the fabrication and characterization of PLECs having different compositions and thickness, and the results were faced up to the models. We showed the existence of critical concentration of salt, below of which the operation of the PLECs are mainly due to injection stimulated by the ionic double-layer. For higher applied voltages, the injection still exists but it is followed by a PIN junction formation. We also verified that for voltages above the turn-on the device electrical resistance is proportional to the sample thickness and is practically temperature-independent. Our results showed that for low voltages the transport is dominated by diffusion, but as the voltage increases, the semiconducting layer starts to be doped: p-type in one side, and n-type in the other. Therefore, the conductivity of the semiconducting layer increases, and it finalizes by the formation of the PIN junction. Finally, we showed that the double-layer characteristic does not depend on the electronic polymer, and that the value of the turn-on voltage is very close to that of the electronic gap of the forbidden band.

L’électronique organique est un nouveau domaine de recherche qui combine les propriétés électriques de l’électronique avec les propriétés mécanique des matériaux organiques. De nouvelles applications telles que des écrans flexibles, de l’éclairage de surface ou des cellules photovoltaïques flexibles, qui ne sont pas possible avec l’électronique basée sur le silicium, sont envisagées. Les semi-conducteurs organiques sont les matériaux clés de ces dispositifs électroniques. Pour le design moléculaire, deux paramètres doivent être optimisés :l’énergie de réorganisation qui doit être minimisée et l’intégrale de transfert qui doit être maximisée. Avec un noyau aromatique rigide et étendu, les acènes linéaires tels que le pentacène et les anthradithiophènes (ADT) possèdent des énergies de réorganisation parmi les plus petites. Quant à l’intégrale de transfert, son intensité va dépendre de l’arrangement moléculaire qui ne peut malheureusement pas encore être prédit. Divers substituents peuvent être introduit sur le noyau aromatique afin de moduler l’arrangement moléculaire et ainsi maximiser l’intégrale de transfert.<p>Durant cette thèse, nous nous sommes intéressés à l’amélioration du transport de charge des anthradithiophènes par design moléculaire. Deux approches ont été envisagées :l’approche moléculaire et l’approche macromoléculaire. L’approche moléculaire se base sur les travaux de Takimiya sur les naphtodithiophènes. Dans ces travaux, il est montré que la mobilité de charge est supérieure lorsque l’isomère anti est utilisé plutôt que l’isomère syn. Les anthradithiophènes sont généralement utilisés en tant que mélange d’isomères syn et anti ;ceci est une conséquence de la voie de synthèse utilisée. Il est raisonnable de penser qu’utiliser des ADT isomériquement purs donnera des mobilités de charge plus élevées, à l’instar des naphtodithiophènes. Le premier objectif de cette thèse est donc de développer une méthodologie permettant d’obtenir des ADT isomériquement purs. L’approche macromoléculaire est basée sur les travaux théoriques d’Antoine Van Vooren sur le couplage électronique via pont éthylène (non conjugué). Selon ces calculs, le couplage électronique entre deux noyaux aromatiques est plus important lorsqu’ils sont reliés par un pont éthylène que lorsqu’ils sont indépendants. Le second objectif de cette thèse est de développer une méthodologie qui permet d’attacher deux ADTs via a pont éthylène.<p>Une stratégie de synthèse menant à l’anti-ADT a été développée. La quantité d’anti-ADT disponible via cette méthodologie est assez faible. Par conséquent, une autre méthodologie a été développée. En fonctionnalisant un des intermédiaires de réaction, il est possible de séparer les deux isomères et ainsi d’obtenir de plus grandes quantités d’anti-ADT et de syn-ADT. Les spectres d’absorption UV-vis du mélange et des différents isomères ont été comparés. Des études sur des dispositifs électroniques utilisant des ADT isomériquement purs sont en cours.<p>Une stratégie de synthèse menant à l’ADT ponté a été développée. Dans cette stratégie, le pont éthylène est synthétisé en premier et les entités anthradithiophènes générées dans un deuxième temps. L’ADT ponté a été obtenu à l’état de traces, détectées uniquement par spectrométrie de masse. Des efforts synthétique supplémentaire sont nécessaire afin d’obtenir l’ADT ponté dans des quantités suffisantes pour fabriquer des dispositifs électroniques. La fabrication de dispositifs électroniques est une étape cruciale dans la détermination de l’impact du pont sur la mobilité de charge.<p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Abstract This thesis reports the investigation of color tuning of two types of organic light emitting devices, transistors (OLETs) and diodes (OLEDs). Voltage tunable two color light emission was demonstrated for OLETs. For OLEDs, two kinds of color tuning methods were presented. For these, color tuning was realized using thermal annealing which changes the light emission color of the devices permanently. The two color light emission of the OLETs, employing a three-layer heterostructure device configuration, occurs in red and green. The device structure was first utilized for producing red light emission originating from a light emission layer made of Alq3:DCM that was deposited between the hole and electron transport layers made of DH-4T and DFH-4T, respectively. After modifying the fabrication process in order to raise the device performance by acquiring smoother active layers green light could also be produced by the devices. Green light emission originated from the electron transport layer. This took place during the electron transport mode, while the red emission was apparent while hole transport was active. The color of the light emission was therefore demonstrated as being tunable by voltage. For OLEDs, devices with one active polymeric layer, undoped and doped, were investigated. The undoped OLEDs had the light emission layer made of blue light emitting polyfluorene PFO. The OLEDs suffered from keto-defects shifting their light emission color from blue to greenish shade, a common problem occurring in widely used blue light emitting polyfluorenes. The work conducted and reported in this thesis demonstrated that thermal annealing can be used for diminishing this undesired green emission. For the doped OLEDs with the light emission layer made of a PFO:F8BT blend, color tuning was realized using thermal annealing as well. As a result of exposure to thermal treatment, the light emission color of these devices which was green as fabricated was converted to white. The phenomenon behind this effect was explained by phase separation between the host and dopant polymers of the light emission layer. / Tiivistelmä Tässä väitöskirjatyössä tutkitaan orgaanisten valoa emittoivien transistoreiden (OLET) ja diodien (OLED) värinsäätöä. Työssä tehtiin kolmikerrosrakenteisia OLETeja, jotka kykenevät emittoimaan valoa kahdella värillä ja joiden emittointiväri on jännitesäädettävissä. OLEDien osalta toteutettiin kaksi erilaista värinsäätömenetelmää, joissa molemmissa hyödynnettiin kuumennusta pysyvän värinvaihdon aikaansaamiseksi. Tutkitut OLETit emittoivat punaista ja vihreää valoa. Aluksi tutkittiin vastaavia komponentteja, jotka emittoivat vain punaista valoa. Näissä komponenteissa punaisen valon tuotti keskimmäinen valoemitterinä toiminut kerros (Alq3:DCM), jonka ala- ja yläpuolella olivat aukko- ja elektronijohtavat kerrokset (DH-4T ja DFH-4T). Komponenteilla saatiin tuotettua myös vihreää valoa, kun valmistusprosessia kehitettiin tasaisempien aktiivisten materiaalikerrosten valmistamiseksi. Vihreän valon todettiin olevan elektronijohtavan kerroksen tuottamaa. Kaksiväriemittoiva OLET tuotti vihreää valoa ollessaan elektronijohtavassa tilassa, ja punaista valoa aukkojohtavassa tilassa, emittointivärin ollessa näin jännitesäädettävissä. Työssä tutkittujen OLEDien valon emittointi perustui polymeerikerrokseen, joka oli toisissa OLEDeissa seostamaton ja toisissa seostettu. Seostamattomien OLEDien aktiivinen kerros oli tehty sinistä valoa tuottavasta polyfluoreenista (PFO), jossa usein ilmenee keto-virheitä, joiden vuoksi PFO:sta tehtyjen OLEDien valo muuttuu sinisestä vihertäväksi. Työssä osoitettiin, että kuumennusta voidaan käyttää sinisen emittointivärin palauttamiseen. Seostettujen OLEDien (PFO:F8BT) osalta kuumennusta käytettiin komponenttien emittointivärin muuttamiseksi alkuperäisestä emittointiväristä vihreästä valkoiseksi. Tämä ilmiö selitettiin valoa emittoivan kerroksen polymeerien välisellä faasierkaantumisella.

Les diodes organiques électroluminescentes (OLEDs), dans lesquelles l’émission de couleur provient de la fluorescence de molécules organiques, représentent une évolution de la technologie des diodes électroluminescentes (LED) classiques. Les OLEDs phosphorescentes (PhOLEDs) permettre d’atteindre des rendements plus élevée que les OLEDs, en utilisant comme couche émissive un couple « matériau organique/dopant phosphorescent ». Ce travail porte sur la synthèse et l'étude de nouvelles molécules à haut état triplet, pour des applications comme matrices hôtes dans des PhOLEDs bleues. Après une introduction à ce domaine novateur, la synthèse de nouveaux semi-conducteurs organiques dérivés de l’architecture 2π-1spiro et l’analyse détaillée des propriétés physico-chimiques sont présentées. Les performances de PhOLEDs bleues utilisant ces nouvelles matrices sont alors décrites et montrent l’intérêt du design de ces nouvelles molécules hôtes. / Organic light emitting diodes (OLEDs) in which light is emitted from fluorescence pathway of an organic molecule, represent an evolution of the light emitting diode (LED) technology. Phosphorescent OLEDs (PhOLEDs) which combine in the emitting layer an “organic host doped with a guest phosphor”, may reach theoretically higher performances than OLEDs. This work is focused on the synthesis and the study of new organic compounds with high triplet state energy, which will be used as host material in blue PhOLEDs. After an introduction of this important field of organic electronics, the synthesis of new organic semi-conductors based on the 2π-1spiro architecture and the detailed analysis of their physicochemical properties through a structure/properties relationship study are presented. The performances of blue PhOLEDs using these matrices are then described and show the great interest of the new host designs.