La compréhension des interrelations entre la microstructure et les processus électroniques dans les polymères semi-conducteurs est d’une importance primordiale pour leur utilisation dans des hétérostructures volumiques. Dans cette thèse de doctorat, deux systémes diffèrents sont étudiés ; chacun de ces systèmes représente une approche diffèrente pour optimiser les matériaux en termes de leur microstructure et de leur capacité à se mettre en ordre au niveau moléculaire. Dans le premier système, j’ai effectué une analyse complète des principes de fonctionnement d’une cellule photovoltaïque hybride à base des nanocristaux d’oxyde de zinc (ZnO) et du poly (3-hexylthiophène) (P3HT) par absorption photoinduite en régime quasi-stationnaire (PIA) et la spectroscopie PIA en pompage modulé dépendant de la fréquence. L’interface entre le donneur (le polymère P3HT) et l’accepteur (les nanoparticules de ZnO), où la génération de charges se produit, joue un rôle important dans la performance des cellules photovoltaïques hybrides. Pour améliorer le mécanisme de génération de charges du P3H: ZnO, il est indispensable de modifier l’interface entre ses constituants. Nous avons démontré que la modification d’interface moléculaire avec cis-bis (4, 40 - dicarboxy-2, 20bipyridine) ruthénium (II) (N3-dye) et a-Sexithiophen-2 yl-phosphonique (6TP) a améliorée le photocourant et la performance dans les cellules P3HT: ZnO. Le 6TP et le N3 s’attachent à l’interface du ZnO, en augmentant ainsi l’aire effective de la surface donneur :accepteur, ce qui contribue à une séparation de charge accrue. De plus, le 6TP et le N3 réduisent la densité de pièges dans le ZnO, ce qui réduit le taux de recombinaison des paires de charges. Dans la deuxième partie, jai introduit une matrice hôte polymérique de polystyréne à masse molaire ulra-élevée, qui se comporte comme un solide pour piéger et protéger une solution de poly [2-méthoxy, 5- (2´-éthyl-hexoxy) -1,4-phénylènevinylène- PPV] (MEHPPV) pour utilisation dans des dispositifs optoèlectroniques quantiques. Des travaux antérieurs ont montré que MEH-PPV en solution subit une transition de conformation, d’une conformation enroulé à haute température (phase bleue) à une conformation de chaîne étendue à basse température (phase rouge). La conformation de la chaîne étendue de la solution MEH-PPV favorise les caractéristiques nécessaires à l’amélioration des dispositifs optoélectroniques quantiques, mais la solution ne peut pas être incorporées dans le dispositif. J’ai démontré que la caractéristique de la phase rouge du MEH-PPV en solution se maintient dans une matrice hôte polymérique de polystyrène transformé de masse molaire très élevée, qui se comporte comme un solide (gel de MEH-PPV/UHMW PS), par le biais de la spectroscopie de photoluminescence (PL) dépendant de la température (de 290K à 80 K). La phase rouge du gel MEH-PPV/UHMW PS se manifeste par des largeurs de raie étroites et une intensité augmentée de la transition 0-0 de la progression vibronique dans le spectre de PL ainsi qu’un petit décalage de Stokes entre la PL et le spectre d’absorption à basse température. Ces approches démontrent que la manipulation de la microstructure et des propriétés électroniques des polymères semi-conducteurs ont un impact direct sur la performance de dispositifs pour leurs développements technologiques continus. / Understanding the interrelations between microstructure and electronic processes in polymeric semiconductors is of great importance for their use in bulk heterostructures, as the active part of power-converting devices such as organic photovoltaic cells or light emitting diodes, as well as for quantum optoelectronics applications. In this doctoral thesis, two different systems are investigated; each of these systems represents a different approach to optimize materials in terms of microstructure and their ability to order on the molecular level. In the first system, by means of quasi-steady-state photoinduced absorption (PIA) and pump-modulation-frequency-dependent PIA spectroscopy, I performed a comprehensive analysis of the working principles of a hybrid photovoltaic cell based on nanocrystals of zinc oxide (ZnO) and poly(3-hexylthiophene) (P3HT). The interface surface area between donor (polymer P3HT) and acceptor (ZnO nanocrystals), where charge generation occurs, plays a significant role in the performance of the hybrid photovoltaic cells. To improve the charge generation mechanism of P3HT: ZnO, it is therefore essential to modify the P3HT: ZnO interface area. We demonstrated that molecular interface modification with cis-bis(4,40-dicarboxy-2,20bipyridine) ruthenium (II) (N3-dye) and a-Sexithiophen-2-yl-phosphonic Acid (6TP) as interface modifiers enhanced the photocurrent and performance in P3HT: ZnO cells. 6TP and N3 attach to the ZnO interface, thus increasing the donor:acceptor interface area that contributes to enhanced charge separation. Furthermore, 6TP and N3 reduce the ZnO traps that reduces recombination. In the second part, I introduced a processed solid-like ultra-high-molecular-weight polystyrene polymeric host matrix to trap and protect poly [2-methoxy, 5-(2’-ethylhexoxy)- 1,4-phenylene vinylene-PPV] (MEH-PPV) solution for use in quantum optoelectronic devices. Previous work by others has shown that MEH-PPV in solution undergoes a conformation transition from coiled conformation at high temperatures (blue-phase) to a chain-extended conformation at low temperatures (red-phase). The chain-extended conformation of MEH-PPV solution favours the characteristics needed to improve quantum optoelectronic devices, however the solution cannot be incorporated into the device. We demonstrated that the red-phase feature of MEH-PPV in solution maintains in a processed solid-like ultra-high-molecular-weight polystyrene polymeric host matrix (MEH-PPV/UHMWPS gels), by means of temperature-dependent photoluminescence (PL) spectroscopy (ranged from 290K down to 80 K). The red-phase of MEH-PPV/UHMW PS gels manifest itself as narrow linewidths and enhanced 0-0 line strength in the PL spectrum as well as a small stokes shifts between the PL and absorption spectra at low temperatures. These approaches demonstrate that microstructure manipulation and electronic properties of polymeric semiconductors have a direct impact on the device performance for their continued technological developments.

Ce travail de recherche pluridisciplinaire a consisté en l'étude de cellules photovoltaïques organiques à base de nouveaux copolymères à blocs de type rigide-flexible. L'idée était de proposer une alternative aux mélanges donneur/accepteur, dont la morphologie en film est très difficile à contrôler, en élaborant de nouveaux matériaux conjugués capables de s'auto-organiser et de créer une nano-structuration de la couche active, permettant ainsi d'optimiser certains paramètres du processus photovoltaïque (dissociation de l'exciton, conduction des charges vers les électrodes). La première étape a consisté à développer une synthèse simplifiée et versatile de copolymères constitués d'un bloc conjugué donneur (poly(3-hexylthiophène), d'un bloc flexible polystyrène, et d'un accepteur d'électron (C60). La seconde étape a consisté à caractériser ces matériaux originaux en tant que couche active ou compatibilisants dans des dispositifs photovoltaïques organiques et ainsi montrer leur potentiel. / This multidisciplinary work deals with the study of organic photovoltaic cells based on new rod-coil block copolymers. The aim was to replace donor/acceptor blends which are currently limited by poor control over their thin-film morphology. It was expected that the new materials may self-assemble to give a nano-structuration of the active layer, and thereby optimize the principal physical photovoltaic processes, namely exciton separation and conduction of charge-carriers through the film to the electrodes. A versatile and simplified synthesis of rod-coil copolymers consisting of a donor conjugated block [poly(3-hexylthiophene], a flexible block (polystyrene) and an electron acceptor (C60) was developed. The characterization of the new materials demonstrated their potential as an active layer or compatibilizer in photovoltaic devices.

Esta tese tem por objetivo o desenvolvimento de metodologias eficientes e de baixo custo para ajustar as propriedades elétricas de OFETs de canal p e de canal n, a fim de possibilitar a fabricação do circuito complementar orgânico, semelhante a uma estrutura CMOS. O desempenho do circuito complementar fabricado foi otimizado, e também foi confeccionado por impressão um OFETs de canal operando em baixas tensões. Para a fabricação do CMOS orgânico foi proposto um método baseado na seleção adequada do solvente da camada dielétrica para ajustar o desempenho elétrico dos OFETs de canal p e de canal n. Os solventes, MEK, nBA e DMSO foram selecionados para a dissolução do PMMA por apresentarem diferenças nos valores de momento de dipolo, de ponto de ebulição e de graus de ortogonalidade em relação as camadas semicondutoras de P3HT e de P(NDI2OD-T2) dos OFETs. A análise dos resultados dos OFETs de canal p e de canal n demonstrou que a metodologia proposta é adequada tanto para o ajuste das propriedades elétricas destes dispositivos quanto para a otimização do desempenho dos mesmos. Os melhores desempenhos elétricos para os OFETs de canal p e de canal n foram obtidos quando utilizados o DMSO e o MEK como solventes do PMMA, respectivamente, devido à perfeita ortogonalidade destes solventes em relação às camadas semicondutoras. Os OFETs de canal p que utilizaram o DMSO e os OFETs de canal n que utilizaram o nBA foram os que apresentaram desempenhos elétricos semelhantes, sendo portanto aplicados na fabricação do CMOS. Valores de ganho entre 6,8 e 7,8 e de margem de ruído entre 28,3 V e 34,5 V foram obtidos para inversores complementares fabricados nesta etapa do trabalho. OFETs de canal p utilizando uma blenda de PTAA: diF TES ADT como camada semicondutora, o PEDOT:PSS como eletrodos dreno/fonte e o P(VDF-TrFE-CFE) como camada dielétrica também foram fabricados neste trabalho. A técnica de blade-coating foi utilizada para a deposição dos eletrodos dreno/fonte e da camada semicondutora, ao passo que a técnica de spray-coating foi utilizada para a deposição da camada dielétrica. Da análise dos resultados foi possível inferir que a utilização de um dielétrico com elevada constante dielétrica (K), como o P(VDF-TrFE-CFE), possibilita o funcionamento dos transistores a baixas tensões (≤ 8 V), porém com valores de mobilidade reduzidos devido à elevada desordem dipolar na interface provocada por este dielétrico. Para minimizar esses efeitos, uma fina camada de um polímero fluorado foi depositada entre a camada semicondutora e a dielétrica pela técnica de blade-coating, constituindo assim uma bicamada dielétrica nos OFETs. Dos resultados das medidas elétricas dos OFETs constituídos pela bicamada dielétrica foi observada permanência do funcionamento destes dispositivos a tensões inferiores a 8 V com desempenho elétricos superiores a resultados já publicados na literatura. Por fim, inversores lógicos unipolares com transistores de carga foram fabricados com os OFETs que utilizaram a bicamada dielétrica, sendo obtidos valores de ganho entre 1,2 e 1,6 e de margem de ruído entre 56% e 68,5% de ½ VDD. / This thesis aimed to develop an efficient and low cost method to adjust the electrical properties of p- and n-channel OFETs to allow us to build an organic CMOS and the optimization of printed p-channel OFETs to work at low voltages. We proposed a method to fabricate the organic CMOS, based on the careful selection of dielectric solvent, which was adjusted to obtain the best performance of p- and n-channel OFETs. The dielectric solvents as MEK, nBA and DMSO were selected to dissolve the PMMA dielectric polymer due their different physical properties as dipole moment and boiling point and because they showed slightly different degrees of orthogonality to the P3HT and P(NDI2OD-T2) semiconductor layers of the OFETs. The results showed that the careful selection of the dielectric solvent not only allows to tune the electrical characteristics of the p- and n-channel OFETs, but also to improve the performance of these devices. The best performances were achieved when DMSO and MEK were used as dielectric solvents of the p and n-channel OFETs, respectively, as result of the perfectly orthogonality of these solvents to the semiconductor layers. P-channel OFETs using DMSO and n-channel OFETs using nBA showed similar electrical characteristics and thus, they were used to construct the organic CMOS. The organic complementary inverters showed high gain and noise margin values in the range of 6,8 to 7,8 and 28,3 V to 34,5 V, respectively. Printed p-channel OFETs were also fabricated, in which the blend PTAA:diF TES ADT was used as semiconductor channel, PEDOT:PSS as the drain/source electrodes and P(VDF-TrFE-CFE) as the dielectric layer. The blade-coating technique was used to deposit the source/drain electrodes and the semiconductor layer, while the spray-coating technique was used to deposit the dielectric layer. It was observed that using high-k dielectric as P(VDF-TrFE-CFE) enable to reduce the operating voltage of the OFETs (≤8 V), however, this high-k dielectric also reduced the field effect mobility due the dipolar disorder at the semiconductor/dielectric interface. To minimize the dipolar issue at the interface, we inserted a thin fluoropolymer dielectric layer by blade-coating between the semiconductor and the high-k dielectric layers, thus constituting a dielectric bilayer on the OFETs. From the electrical measurements of the OFETs with the dielectric bilayer, it was observed that the devices were still working at 8 V and they also showed better performance in comparison to results already published. Finally, organic unipolar inverters with load transistors were fabricated using the p-channel OFETs with the dielectric bilayer and they showed reasonable performance, with gain and noise margin in the range of 1,2 to 1,6 and 56% e 68,5% of ½ VDD, respectively.

Esta tese tem por objetivo o desenvolvimento de metodologias eficientes e de baixo custo para ajustar as propriedades elétricas de OFETs de canal p e de canal n, a fim de possibilitar a fabricação do circuito complementar orgânico, semelhante a uma estrutura CMOS. O desempenho do circuito complementar fabricado foi otimizado, e também foi confeccionado por impressão um OFETs de canal operando em baixas tensões. Para a fabricação do CMOS orgânico foi proposto um método baseado na seleção adequada do solvente da camada dielétrica para ajustar o desempenho elétrico dos OFETs de canal p e de canal n. Os solventes, MEK, nBA e DMSO foram selecionados para a dissolução do PMMA por apresentarem diferenças nos valores de momento de dipolo, de ponto de ebulição e de graus de ortogonalidade em relação as camadas semicondutoras de P3HT e de P(NDI2OD-T2) dos OFETs. A análise dos resultados dos OFETs de canal p e de canal n demonstrou que a metodologia proposta é adequada tanto para o ajuste das propriedades elétricas destes dispositivos quanto para a otimização do desempenho dos mesmos. Os melhores desempenhos elétricos para os OFETs de canal p e de canal n foram obtidos quando utilizados o DMSO e o MEK como solventes do PMMA, respectivamente, devido à perfeita ortogonalidade destes solventes em relação às camadas semicondutoras. Os OFETs de canal p que utilizaram o DMSO e os OFETs de canal n que utilizaram o nBA foram os que apresentaram desempenhos elétricos semelhantes, sendo portanto aplicados na fabricação do CMOS. Valores de ganho entre 6,8 e 7,8 e de margem de ruído entre 28,3 V e 34,5 V foram obtidos para inversores complementares fabricados nesta etapa do trabalho. OFETs de canal p utilizando uma blenda de PTAA: diF TES ADT como camada semicondutora, o PEDOT:PSS como eletrodos dreno/fonte e o P(VDF-TrFE-CFE) como camada dielétrica também foram fabricados neste trabalho. A técnica de blade-coating foi utilizada para a deposição dos eletrodos dreno/fonte e da camada semicondutora, ao passo que a técnica de spray-coating foi utilizada para a deposição da camada dielétrica. Da análise dos resultados foi possível inferir que a utilização de um dielétrico com elevada constante dielétrica (K), como o P(VDF-TrFE-CFE), possibilita o funcionamento dos transistores a baixas tensões (≤ 8 V), porém com valores de mobilidade reduzidos devido à elevada desordem dipolar na interface provocada por este dielétrico. Para minimizar esses efeitos, uma fina camada de um polímero fluorado foi depositada entre a camada semicondutora e a dielétrica pela técnica de blade-coating, constituindo assim uma bicamada dielétrica nos OFETs. Dos resultados das medidas elétricas dos OFETs constituídos pela bicamada dielétrica foi observada permanência do funcionamento destes dispositivos a tensões inferiores a 8 V com desempenho elétricos superiores a resultados já publicados na literatura. Por fim, inversores lógicos unipolares com transistores de carga foram fabricados com os OFETs que utilizaram a bicamada dielétrica, sendo obtidos valores de ganho entre 1,2 e 1,6 e de margem de ruído entre 56% e 68,5% de ½ VDD. / This thesis aimed to develop an efficient and low cost method to adjust the electrical properties of p- and n-channel OFETs to allow us to build an organic CMOS and the optimization of printed p-channel OFETs to work at low voltages. We proposed a method to fabricate the organic CMOS, based on the careful selection of dielectric solvent, which was adjusted to obtain the best performance of p- and n-channel OFETs. The dielectric solvents as MEK, nBA and DMSO were selected to dissolve the PMMA dielectric polymer due their different physical properties as dipole moment and boiling point and because they showed slightly different degrees of orthogonality to the P3HT and P(NDI2OD-T2) semiconductor layers of the OFETs. The results showed that the careful selection of the dielectric solvent not only allows to tune the electrical characteristics of the p- and n-channel OFETs, but also to improve the performance of these devices. The best performances were achieved when DMSO and MEK were used as dielectric solvents of the p and n-channel OFETs, respectively, as result of the perfectly orthogonality of these solvents to the semiconductor layers. P-channel OFETs using DMSO and n-channel OFETs using nBA showed similar electrical characteristics and thus, they were used to construct the organic CMOS. The organic complementary inverters showed high gain and noise margin values in the range of 6,8 to 7,8 and 28,3 V to 34,5 V, respectively. Printed p-channel OFETs were also fabricated, in which the blend PTAA:diF TES ADT was used as semiconductor channel, PEDOT:PSS as the drain/source electrodes and P(VDF-TrFE-CFE) as the dielectric layer. The blade-coating technique was used to deposit the source/drain electrodes and the semiconductor layer, while the spray-coating technique was used to deposit the dielectric layer. It was observed that using high-k dielectric as P(VDF-TrFE-CFE) enable to reduce the operating voltage of the OFETs (≤8 V), however, this high-k dielectric also reduced the field effect mobility due the dipolar disorder at the semiconductor/dielectric interface. To minimize the dipolar issue at the interface, we inserted a thin fluoropolymer dielectric layer by blade-coating between the semiconductor and the high-k dielectric layers, thus constituting a dielectric bilayer on the OFETs. From the electrical measurements of the OFETs with the dielectric bilayer, it was observed that the devices were still working at 8 V and they also showed better performance in comparison to results already published. Finally, organic unipolar inverters with load transistors were fabricated using the p-channel OFETs with the dielectric bilayer and they showed reasonable performance, with gain and noise margin in the range of 1,2 to 1,6 and 56% e 68,5% of ½ VDD, respectively.

Il est reconnu que la structure des semi-conducteurs organiques influence la sensibilité et la sensitivité des capteurs des gaz. Pour améliorer la compréhension des mécanismes sous-jacents dans les capteurs à base des transistors d’effet de champ organique (OFETs) cette thèse a exploré trois pistes différentes : L’utilisation de l’hystérésis des caractéristiques de transfert comme paramètre de détection des gaz est étudié. En ajoutant l’hystérésis aux paramètres standards, on améliore la sélectivité des OFETs à base de poly(3-hexylthiophène) aux gaz polaires. Des mesures transitoires de courant indiquent que la cinétique de piégeage et de piégeage des porteurs de charges est à l’origine de cette amélioration. Pour comprendre l’influence qu’à la structure moléculaire sur la sensibilité aux vapeurs d’éthanol, des polymères avec des chaînes latérales alcoxyle dont on fait varier la polarité ainsi que l’encombrement stérique, ont été étudiés. L’intensité de la réponse est corrélée avec la quantité d’analyte absorbée et le moment dipolaire des chaînes latérales. Pour permettre l’étude des mécanismes à l’échelle nanométrique, une partie de ce travail se concentre sur la fabrication de transistors avec une taille de canal réduite. En utilisant le nitrure de silicium comme couche diélectrique, on réduite les tensions de commande et les propriétés chimiques à l’interface. / The molecular structure of organic semiconductors which can be tailored by the chemical synthesis influences the sensitivity and selectivity of gas sensor devices. To improve the understanding of the ongoing mechanisms in sensors based on organic field effect transistors (OFETs) this thesis follows three different tracks: The applicability of the hysteresis of the transfer characteristics as a gas sensing parameter is studied. As a complement to the standard transistor parameters the hysteresis improves the selectivity of poly(3-hexylthiophen-2,5-diyl) based OFETs to polar gases. Transient current measurements indicate the additional dependence on the detrapping kinetics as origin of the increased selectivity. To understand the influence of the molecular structure on the gas sensing behavior, polymers with alkoxy side chains, varying in polarity and steric hindrance, are used as gas sensing layer for ethanol vapor. The response strength correlates with the amount of absorbed analyte and the dipole moment of the side chains. To enable investigations of the mechanisms at the nanoscale, one part of this work focuses on the preparation of transistors with a reduced channel length. By using silicon nitride as dielectric layer, driving voltages decreased and interface properties could be improved.

L’optimisation de la morphologie de la couche active est primordiale pour l’augmentation des rendements des cellules solaires photovoltaïques organiques. Nous avons montré l’influence du ratio de matériaux donneur (P3HT) et accepteur (PCBM) d’électrons ainsi que de la masse molaire du P3HT sur la morphologie de la couche active. Afin de contrôler la séparation de phases entre les matériaux donneur et accepteur d’électrons, il est possible d’utiliser des copolymères à blocs afin d’aider la compatibilisation entre le P3HT et le PCBM. Nous avons choisi de synthétiser des copolymères à blocs P3HT-b-polystyrène et des P3HT-b-polyisoprène présentant une certaine compatibilité avec les matériaux de la partie active. L’ajout optimisé de P3HT-b-polyisoprène permet une augmentation de 30% des rendements et de 90% de durée de vie des cellules solaires. / Active layer morphology optimization is fundamental to achieve high efficiency in organic photovoltaic solar cells. We showed the influence of the donor (P3HT) and acceptor (PCBM) material ratio and the impact of the P3HT molecular weight on the active layer morphology. We demonstrated the possibility of using well-designed block copolymers to help P3HT and PCBM compatibilization and to control their phase separation. We chose to synthesize P3HT-b-polystyrene and P3HT-b-polyisoprene for which each block is compatible with the active materials. Optimal addition of P3HT-b-polyisoprene enables to get a 30%-improved efficiency and a 90%-enhanced lifetime of the solar cells.

In this work we investigated fabrication of semiconductor nanomaterials and evaluated their potential for photo-chemical and photovoltaic applications. We investigated different II-VI semiconductor nanomaterial systems; (i) ZnO oriented nanowire arrays non-epitaxially grown from a substrate; and (ii) colloidal CdE (E=Te,Se,S) quantum structures synthesized by solution-based thermal decomposition of organo-metallic precursors. We have studied the synthesis of vertically aligned ZnO nanowire arrays (NWA), by a wet chemical process on various substrates. We have extended this method wherein nanofibers of poly-L-lactide act as a substrate for the radially oriented growth of ZnO nanowires. By combining the large surface area and the flexibility of the PLLA-ZnO hierarchical nanostructure we have shown the proof-of-principle demonstration of a ‘continuous-flow’ water treatment system to decompose known organic pollutants in water, as well as render common waterborne bacteria non-viable. We have studied synthesis of colloidal quantum dots (QD), and show size, morphology and composition tailored nanocrystals for CdE (E=S, Se, Te) compositions. We have studied the influence of crystal growth habits of the nanocrtsyals on the final morphology. Furthermore we have synthesized core-shell, CdSe-CdS QDs with spherical and tetrahedral morphologies by varying the reaction conditions. We show that these core-shell quantum dots show quasi-type II characteristics, and demonstrate with I-V measurements, the spatial localization of the charge carriers in these hetero-nanocrystals. For this purpose, we developed hybrid materials consisting of the core-shell quantum dots with electron acceptors (ZnO nanowires) and hole acceptors (polymeric P3HT nanofibers). In addition we have also compared the synthesis reaction when carried out with conventional heating and microwave-mediated heating. We find that the reaction is enhanced, and the yield is qualitatively better when using microwave induced heating. / QC 20120525

Label-free detection of DNA has been successfully demonstrated on field effect transistor (FET) based devices. Since conducting organic materials was discovered and have attracted more and more research efforts by their profound advantages, this work will focus on utilizing an organic field effect transistor (OFET) as DNA sensor. An OFET constructed with a transporting fluidic channel, WetOFET, forms a fluid-polymer (active layer) interface where the probe DNA can be introduced. DNA hybridization and non-hybridization after injecting target DNA and non-target DNA were monitored by transistor characteristics. The Hysteresis area of transfer curve increased after DNA hybridization which may be caused by the increasing electrostatic screening induced by the increasing negative charge from target DNA. The different morphology of coating surface could also influence the OFET response.

<p>Label-free detection of DNA has been successfully demonstrated on field effect transistor (FET) based devices. Since conducting organic materials was discovered and have attracted more and more research efforts by their profound advantages, this work will focus on utilizing an organic field effect transistor (OFET) as DNA sensor.</p><p>An OFET constructed with a transporting fluidic channel, WetOFET, forms a fluid-polymer (active layer) interface where the probe DNA can be introduced. DNA hybridization and non-hybridization after injecting target DNA and non-target DNA were monitored by transistor characteristics. The Hysteresis area of transfer curve increased after DNA hybridization which may be caused by the increasing electrostatic screening induced by the increasing negative charge from target DNA. The different morphology of coating surface could also influence the OFET response.</p>

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.