Esta tese de doutorado é resultado do estudo da fotocondutividade em materiais poliméricos, com particular enfoque em diodos poliméricos com camada ativa de derivados do poli (p-fenileno vinileno) (PPV): OC10-PPV, SY e MEH-PPV, em estrutura tipo sanduíche (ITO/polimérico/Metal) de camada única, utilizando eletrodos metálicos com diferentes funções trabalho depositados sobre o mesmo filme. Para isso, foi necessária a realização de todas as etapas de fabricação de dispositivos orgânicos, como descritas neste trabalho, para obter resultados com o máximo de reprodutibilidade, bem como o domínio das técnicas de caracterização. As propriedades ópticas dos filmes poliméricos foram analisadas através dos espetros de absorção e de fluorescência estacionária na região do visível. O comportamento fotocondutivo dos dispositivos foi realizado através de medidas de corrente-tensão (I-V) e da espectroscopia de fotocorrente no estado estacionário em regime dc sob incidência de luz com diferentes comprimentos de onda, ora através do ITO, ora através dos eletrodos metálicos semitransparente, para o dispositivo sob diferentes valores de tensões aplicadas. A variação desses parâmetros permitiu verificar como estes influenciam na fotogeração e no transporte de portadores de cargas e assim adaptar e aplicar um modelo teórico que levasse em consideração o campo elétrico aplicado para ajustar a fotocorrente obtida experimentalmente, obtendo informações sobre as propriedades de fotocondutividade dos materiais estudos. / This thesis is a study about photoconductivity in polymeric materials, in particular diodes with single-layer sandwich structure derivates of poly(para-phenylene vinylene) (PPV): OC10-PPV, SY and MEH-PPV. Different metallic electrodes were deposited on the same polymeric layer. Therefore, it was necessary to realize the devices fabrication process step by step as well to dominate the characterization techniques. The optical properties of polymeric film were analyzed through the absorption and emission spectrum in the visible region. The photoconductivity behavior was studied by dc current-voltage (I-V) and photocurrent action spectra through the absorption and emission spectrum in the visible region. The photoconductivity behavior was studied by dc current-voltage (I-V) and photocurrent action spectra through the both side of device under applied voltages. The variation of these parameters allowed verifying how are influencing in the charge carrier photo-generation and the charge transport and then to adapt and apply a theoretical model wich considers the electric field applied to fit the photocurrent action spectra of devices. The values of the parameters allow to survey important about photoconductivity properties of the materials

Esta tese de doutorado é resultado do estudo da fotocondutividade em materiais poliméricos, com particular enfoque em diodos poliméricos com camada ativa de derivados do poli (p-fenileno vinileno) (PPV): OC10-PPV, SY e MEH-PPV, em estrutura tipo sanduíche (ITO/polimérico/Metal) de camada única, utilizando eletrodos metálicos com diferentes funções trabalho depositados sobre o mesmo filme. Para isso, foi necessária a realização de todas as etapas de fabricação de dispositivos orgânicos, como descritas neste trabalho, para obter resultados com o máximo de reprodutibilidade, bem como o domínio das técnicas de caracterização. As propriedades ópticas dos filmes poliméricos foram analisadas através dos espetros de absorção e de fluorescência estacionária na região do visível. O comportamento fotocondutivo dos dispositivos foi realizado através de medidas de corrente-tensão (I-V) e da espectroscopia de fotocorrente no estado estacionário em regime dc sob incidência de luz com diferentes comprimentos de onda, ora através do ITO, ora através dos eletrodos metálicos semitransparente, para o dispositivo sob diferentes valores de tensões aplicadas. A variação desses parâmetros permitiu verificar como estes influenciam na fotogeração e no transporte de portadores de cargas e assim adaptar e aplicar um modelo teórico que levasse em consideração o campo elétrico aplicado para ajustar a fotocorrente obtida experimentalmente, obtendo informações sobre as propriedades de fotocondutividade dos materiais estudos. / This thesis is a study about photoconductivity in polymeric materials, in particular diodes with single-layer sandwich structure derivates of poly(para-phenylene vinylene) (PPV): OC10-PPV, SY and MEH-PPV. Different metallic electrodes were deposited on the same polymeric layer. Therefore, it was necessary to realize the devices fabrication process step by step as well to dominate the characterization techniques. The optical properties of polymeric film were analyzed through the absorption and emission spectrum in the visible region. The photoconductivity behavior was studied by dc current-voltage (I-V) and photocurrent action spectra through the absorption and emission spectrum in the visible region. The photoconductivity behavior was studied by dc current-voltage (I-V) and photocurrent action spectra through the both side of device under applied voltages. The variation of these parameters allowed verifying how are influencing in the charge carrier photo-generation and the charge transport and then to adapt and apply a theoretical model wich considers the electric field applied to fit the photocurrent action spectra of devices. The values of the parameters allow to survey important about photoconductivity properties of the materials

Ce travail porte sur la conception de nouveaux composés π-conjugués, potentiellement utilisable en électronique organique en tant que matériaux actifs dans des dispositifs tels que les OLEDs, les cellules photovoltaïques et les capteurs optiques. Dans ce but, nous avons exploité le motif silacyclopentadiène appelé également silole, possédant un bon rendement quantique de fluorescence à l'état solide et une excellente conduction des électrons. Dans un premier temps, l'introduction de groupements structurants (triptycène, stilbènes..) sur le silacyclopentadiène a permis de moduler l'arrangement moléculaire dans la couche active et par conséquent, les propriétés d'électroluminescence. Des diodes possédant des performances très encourageantes furent ainsi obtenues. Dans un deuxième temps, des dérivés siloles présentant une structure tridimensionnelle et une architecture spirosilole (accepteur)-bithiophène (donneur) furent synthétisées. Une cellule photovoltaïque basée sur ces édifices présentant des performances encourageantes fut ensuite mis au point. Enfin, l'étude des mécanismes de transfert d'énergie entre un film de polymère fonctionnalisé par un groupement sensible silole et des composés nitroaromatiques nous a permis de réaliser un nouveau type de capteur optique hautement sensible pour la détection d'explosifs. / This work concerns the design of new π-conjugated compounds, potentially useful in organic electronics as active materials in devices such as OLEDs, photovoltaic cells and optical sensors. To this end, silacyclopentadiene, alias silole, groups were used exhibiting high fluorescence quantum yields in the solid state and excellent electron conductivities. Firstly, the introduction of structurizing groups (triptycene, stilbenes etc.) at the silacyclopentadiene allowed tuning of the molecular arrangement in the active layer and, consequently, the electroluminescence properties. Diodes showing very encouraging activities were thus obtained. Secondly, silole derivatives possessing a three-dimensional structure and a spirosilole (acceptor) - bithiophene (donor) architecture were synthesized. A photovoltaic cell based on these molecules was then developed exhibiting encouraging activity. Finally, a study of the mechanisms of energy transfer between a polymer film functionalized by a sensitive silole group and nitroaromatic compounds enabled the development of a new type of highly sensitive optical sensor for the detection of explosives.

This work addresses two substantial problems of organic electronic devices: the controllability and adjustability of performance, and the integration using scalable, high resolution patterning techniques for planar thin-film transistors and novel vertical transistor devices. Both problems are of particular importance for the success of transparent and flexible organic electronics in the future. To begin with, the static behavior in molecular doped organic pin-diodes is investigated. This allows to deduce important diode parameters such as the depletion capacitance, the number of active dopant states, and the breakdown field. Applying this knowledge, organic pin-diodes are designed for ultra-high-frequency applications and a cut-off-frequency of up to 1GHz can be achieved using optimized parameters for device geometry, layer thickness, and dopant concentration. The second part of this work is devoted to organic thin-film transistors, high resolution patterning techniques, as well as novel vertical transistor concepts. In particular, fluorine based photo-lithography, a high resolution patterning technique compatible to organic semiconductors, is introduced fielding the integration of organic thin-film transistors under ambient conditions. However, as it will be shown, horizontal organic thin-film transistors are substantially limited in their performance by charge carrier injection. Hence, down-scaling is inappropriate to enlarge the transconductance of such transistors. To overcome this drawback, a novel vertical thin-film transistor concept with a vertical channel length of ∼50nm is realized using fluorine based photo-lithography. These vertical devices can surpass the performance of planar transistors and hence are prospective candidates for future integration in complex electronic circuits.

This work addresses two substantial problems of organic electronic devices: the controllability and adjustability of performance, and the integration using scalable, high resolution patterning techniques for planar thin-film transistors and novel vertical transistor devices. Both problems are of particular importance for the success of transparent and flexible organic electronics in the future. To begin with, the static behavior in molecular doped organic pin-diodes is investigated. This allows to deduce important diode parameters such as the depletion capacitance, the number of active dopant states, and the breakdown field. Applying this knowledge, organic pin-diodes are designed for ultra-high-frequency applications and a cut-off-frequency of up to 1GHz can be achieved using optimized parameters for device geometry, layer thickness, and dopant concentration. The second part of this work is devoted to organic thin-film transistors, high resolution patterning techniques, as well as novel vertical transistor concepts. In particular, fluorine based photo-lithography, a high resolution patterning technique compatible to organic semiconductors, is introduced fielding the integration of organic thin-film transistors under ambient conditions. However, as it will be shown, horizontal organic thin-film transistors are substantially limited in their performance by charge carrier injection. Hence, down-scaling is inappropriate to enlarge the transconductance of such transistors. To overcome this drawback, a novel vertical thin-film transistor concept with a vertical channel length of ∼50nm is realized using fluorine based photo-lithography. These vertical devices can surpass the performance of planar transistors and hence are prospective candidates for future integration in complex electronic circuits.