The application of organic electronics to display technologies, large area electronic paper (or plastics), organic light emitting diodes (OLEDs), organic solar cells, radio frequency identification tags, smart cards and chemical sensors has received a great deal of attention in recent years. The main advantages of using organic semiconductors (OSCs) are lowcost, low processing temperature, flexibility, light weight and rugged design. The substantial progress in this field has been driven not just by existing technologies, such as flat panel displays, but also by new applications, such as flexible solid-state lighting, lowcost printed integrated circuits, and plastic solar cells, to name a few. Performance-wise, organic thin-film transistors (OTFTs) are on par with their a-Si (amorphous silicon) counterparts. Since OTFT fabrication offers lower processing temperatures and lower cost, it has the potential to replace a-Si in the near future. To date, all organic complementary circuits have used stencil mask patterning. Stencil mask patterning is not practical for mass manufacturing; hence, a way to pattern organic complementary metal-oxide-semiconductor (O-CMOS) using photolithography is paramount. This is the goal of this thesis. In this dissertation the design and fabrication of improved OTFTs for electronic displays and complementary circuits are illustrated. Here, we demonstrated OTFTs that have excellent stability; hence, they are more suitable for the above-mentioned electronic applications. In addition, for the first time, successful photolithographic patterning of an n-channel organic semiconductor is demonstrated. These important results have enabled us to integrate the n-channel and p-channel organic materials using a complete photolithographic process in realizing O-CMOS.

Le travail entre dans le cadre de la nouvelle tendance à la recherche d’une électronique mécaniquement flexible basée sur des transistors en couche mince constitués uniquement de matériaux organiques (OTFT). OTFT de type n et de type p ont été fabriqués par la technique de dépôt par impression (inkjet) et étudiés. Les paramètres d’impression (jetabilité, mouillabilité, imprimabilité et possibilité d’obtention de différentes formes), de chaque encre permettant le dépôt de couches conductrices, isolantes et semiconductrices, ont été systématiquement étudiés. Les OTFT de type n basés sur du C60 se sont montrés non fiables, principalement du fait de la faible solubilité du C60 dans les solvants organiques. Les OTFT de type basés sur du Tips-pentacene ont montré par contre une grande fiabilité. Le travail global constitue une large revue des problèmes et difficultés rencontrés dans la fabrication de transistors fabriqués entièrement par impression jet d’encre. Des solutions ont été trouvées et de nouvelles idées sont proposées. / Present work deals with the new trend to get highly flexible electronics by using fully Organic Thin-Film Transistor (OTFT) as the basic element of this electronics. Fully organic n-type as well as p-type OTFT processed by inkjet printing are studied. Printing parameters of each ink, jettability, wetting, printability, and patterns optimization, leading to the deposition of conductive contacts, gate insulator and semiconducting active layer are studied. Process of n-type OTFT based on C60 is shown as unreliable, mainly due to the poor solubility of C60 in organic solvent. In the contrary, p-type OTFTs based on Tips-pentacene are much more reliable. The work is a large overview of the issues and the difficulties that have been to jump and to solve in the way to fabricate fully printed organic transistors. Some solutions have been given and new ideas have been proposed.

In this work, we have investigated the effects of temperature and optical illumination on organic thin film transistors (OTFTs) with indium-tin-oxide electrode. Experimental results have shown that the turn-on characteristics of the pentacene OTFT with ITO as source/drain electrodes is dependent on environmental temperatures. In addition, it has been found the pentacene OTFT is one kind of photo-sensitive devices. External stimulations can change the I-V characteristics significantly. For example, our pentacene OTFT show a shift of the onset and threshold voltage with illumination, which recovers slowly in the dark. Therefore, except for the application of switch devices, petacene OTFT exhibits a potential application for image sensors.

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Cette thèse a pour objectif de contribuer à la caractérisation et à la modélisation des transistors organiques en couches minces ou OTFTs (Organic Thin Film Transistors). Elle s’est déroulée en partenariat avec le CEA-LITEN qui dispose d'une technologie imprimée ayant démontré sa fonctionnalité à plusieurs reprises. Le but de ce travail est d'abord de comprendre le fonctionnement des transistors organiques afin de déterminer l'impact des paramètres technologiques sur les caractéristiques électriques. Ceci est fait en utilisant une approche par simulation grâce aux paramètres extraits à partir de la mesure. La dépendance en géométrie et en température des paramètres du transistor est observée et étudiée afin de proposer un modèle valide prenant en compte ces variations. Le modèle doit être intégrable dans les flots de conception classiques de la microélectronique (Cadence, Eldo, ADS, etc…). Des modèles de dispersion sont présentés et par la suite utilisés pour la simulation et la réalisation de circuits analogiques organiques. / This thesis focuses on a contribution of organic thin film transistors (OTFTs) characterization and modeling. It takes place in partnership with CEA-LITEN, which has a printed technology. This technology has demonstrated its functionality repeatedly. The goal is to first understand in depth the functioning of the organic transistors to determine the impact of technological parameters on electrical characteristics. This is done using a simulation approach using the parameters extracted from the measurements. The geometry and temperature dependences of the transistor parameters are observed and studied in order to provide a valid model for a wide range of geometry and temperature. The proposed model should respect the following constraints: an integrability in conventional design tools (Cadence, Eldo, ADS, etc...) and must also include a dispersion model. This model is subsequently used to produce blocks of analog circuits.

A range of small molecules of interest for use in organic semiconductor devices were studied computationally. Trends in geometry, absorption spectra, molecular orbitals, electrostatic potentials, reorganisation energies were studied. Results suggest that, as with acenes, the performance of non-linear cata-condensed polyaromatic hydrocarbons improves as number of fused benzene rings increases. The torsion in these molecules did not appear to have a large impact on the conjugation across the core and little effect on the absorption spectra, although it did affect the reorganisation energies on which charge mobilities depend. Computational studies of mobilities of anthradithiophene molecules were broadly able to reproduce trends seen experimentally and emphasised the importance of crystal morphology. Experimental work was also carried out to search for cocrystals between anthradithiophene derivatives. Many examples were found with some mixtures forming different cocrystals at different mixture ratios. These results were rationalised by a computational study that showed molecules which had a similar binding energy were more likely to be able to form cocrystals. Cocrystal devices were fabricated and 3 out of 7 showed a larger mobility than devices made out of its constituent materials alone. The best of these had a mobility 65% higher than a device made out of the constituent material with the largest mobility. An energy decomposition analysis was carried out on a novel thallophilic system, a complex of thallium with a neutral β-triketimine ligand which was found to form dimers with close Tl-Tl interactions. Calculations show the electrostatic interaction to be repulsive for the dimer with no counter ions, but attractive when 3,5-bistrifluoromethylphenyl borate counter ions are included. This suggests the metallophilic interaction is counter ion-mediated, requiring the anions to provide favourable electrostatics, even in the case of spatially diffuse and distant counter ions such used here. To enable the studies described here software was written for simulating absorption spectra. An implementation into the Gaussian Suite of programs of an energy decomposition scheme and its extension to include an empirical dispersion correction was also carried out.