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Polycyclic aromatic hydrocarbons composed of benzenoid rings fused in a linear fashion comprise the class of compounds known as acenes. The structures containing three to six ring fusions are brightly colored and possess band gaps and charge transport efficiencies sufficient for semiconductor applications. These molecules have been investigated throughout the past several decades to assess their optoelectronic properties. The absorption, emission and charge transport properties of this series of molecules has been studied extensively to elucidate structure-property relationships. A wide variety of analogous molecules, incorporating heterocycles in place of benzenoid rings, demonstrate similar properties to the parent compounds and have likewise been investigated. Functionalization of acene compounds by placement of groups around the molecule affects the way in which molecules interact in the solid state, in addition to the energetics of the molecule. The use of electron donating or electron withdrawing groups affects the frontier molecular orbitals and thus affects the optical and electronic gaps of the molecules. The use of bulky side groups such as alkylsilylethynyl groups allows for crystal engineering of molecular aggregates, and changing the volume and dimensions of the alkylsilyl groups affects the intermolecular interactions and thus changes the packing motif. In chapter 2, a series of tetracene and pentacene molecules with strongly electron withdrawing groups is described. The investigation focuses on the change in energetics of the frontier molecular orbitals between the base acene and the nitrile and dicyanovinyl derivatives as well as the differences between the pentacene and tetracene molecules. The differences in close packing motifs through use of bulky alkylsilylethynyl groups is also discussed in relation to electron acceptor material design and bulk heterojunction organic photovoltaic characteristics. Chapter 3 focuses on molecular acceptor and donor molecules for bulk heterojunction organic photovoltaics based on anthrathiophene and benzo[1,2-b:4,5-b’]dithiophene central units like literature molecules containing fluorene and dithieno[2,3-b:2’,3’-d]silole cores. The synthetic strategies of developing reduced symmetry benzo[1,2-b:4,5-b’]dithiophene to study the effect of substitution around the central unit is also described. The optical and electronic properties of the donors and acceptors are described along with the performance and characteristics of devices employing these molecules. The final two data chapters focus on new nitrogen containing polycyclic hydrocarbons containing indolizine and (2.2.2) cyclazine units. The optical, electronic and other physical properties of these molecules are explored, in addition to the synthetic strategies for incorporating the indolizine and cyclazine units. By use of alkylsilylethynyl groups, crystal engineering was investigated for the benzo[2,3-b:5,6-b’]diindolizine chromophore described in chapter 4 to target the 2-D “brick-work” packing motif for application in field effect transistor devices. Optical and electronic properties of the cyclazine end-capped acene molecules described in chapter 5 were investigated and described in relation to the base acene molecules. In both cases, density functional theory calculations were conducted to better understand unexpected optical properties of these molecules, which are like the linear acene series despite the non-linear attachment.

Le développement des transistors organiques, ces dernières années, a permis une nette amélioration de leurs performances et de leur stabilité. Ceci a été possible, notamment, grâce à une meilleure compréhension des mécanismes régissant le transport de charges dans ces dispositifs. Cependant, certains phénomènes restent encore à éclaircir, en particulier au niveau de l’interface entre le semi-conducteur et le diélectrique. Le piégeage des porteurs de charges qui est une des principales causes de perturbations du transport de charges dans les transistors organiques, en est un. Cette thèse se propose donc, d’étudier ce phénomène dans des transistors à base de pentacène.Les groupements polaires, et plus particulièrement les groupements hydroxyles, présents à l’interface entre l’isolant et le semi-conducteur, sont les principaux responsables du piégeage des porteurs de charges dans les transistors organiques. Afin de limiter leur présence, une technologie basée sur l’emploi d’une couche interfaciale diélectrique passivante, pauvre en groupements hydroxyles, à base de fluorure de calcium, a été mise en place. L’influence de cette couche sur le comportement de transistors à base de pentacène a été étudiée, de même que le vieillissement de ces dispositifs sous différentes conditions de stockage (sous vide et à l’air) et sous contrainte électrique.Ainsi, il a été mis en évidence qu’une couche de fluorure de calcium d’une épaisseur trop importante (de l’ordre de 5 nm) modifie la morphologie de la couche de pentacène, ce qui se traduit par une quasi-disparition du transport de charges dans le pentacène en configuration de transistor à effet de champ. Les études de vieillissement ont montré que sous l’effet de la couche interfaciale de CaF2, même d’une très fine épaisseur (de quelques nanomètres), une quantité plus importante d’humidité est présente dans la couche de pentacène, probablement à cause de la nature hygroscopique du fluorure de calcium. / These recent years, Organic Field-Effect Transistor (OFET) development has significantly improved it performances and it stability. This was made possible, through a better understanding of the mechanisms governing charge transport in these devices. However, some phenomena remain unclear, in particular, at the interface between the semiconductor and the dielectric. Charge carrier trapping which is one of the main causes of charge transport disturbance in organic transistors, is one of them. So, this work aims to investigate such phenomena in pentacene-based transistors.Polar groups and particularly, hydroxyl groups, located at the insulator-semiconductor interface, are the main sources of charge carriers trapping in OFET. To prevent their presence, an OFET fabrication technology based on a passivating dielectric, poor of hydroxyl groups, calcium fluoride-based interfacial layer has been developed. Effect of this layer on pentacene-based transistors operation has been studied, as well as these devices aging under different storage atmosphere (in vacuum and in air) and under electrical stress.Thus, it has been highlighted that an interfacial layer of calcium fluoride with a too high thickness (around 5 nm) changes pentacene layer morphology which results in a quasi-disappearance of charge transport in pentacene in OFET configuration. Aging studies showed that under the effect of CaF2 interfacial layer, even with a very thin thickness (a few nanometers), a greater quantity of moisture is induced in pentacene layer probably due to the hygroscopic nature of calcium fluoride.

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>

A long-term goal within the field of organic electronics has been to developflexible and functional devices, which can be processed and patterned withlow-cost and energy-efficient solution-based methods. This thesis presents anumber of functional paths towards the attainment of this goal via thedevelopment and demonstration of novel fabrication and patterningmethods involving the important organic-semiconductor family termedfullerenes.Fullerenes are soccer-shaped small molecules, with two often-employedexamples being the symmetric C60 molecule and its more soluble derivative[6,6]-phenyl-C61-butyric acid methyl ester (PCBM). We show that PCBM canbe photochemically transformed into a dimeric state in a bi-excited reactionprocess, and that the exposed material features a significantly reducedsolubility in common solvents as well as an effectively retained electronmobility. This attractive combination of material properties allows for adirect and resist-free lithographic patterning of electronic PCBM films downto a smallest feature size of 1 µm, using a simple and scalable two-stepprocess constituting light exposure and solution development. In a furtherdevelopment, it was shown that the two-step method was useful also in thearea-selective transformation of fullerene/conjugated-polymer blend films,as demonstrated through the realization of a functional complementary logiccircuit comprising a 5-stage ring oscillator.In another project, we have synthesized highly flexible, single-crystal C60nanorods with a solution-based self-assembly process termed liquid-liquidinterfacial precipitation. The 1-dimensional nanorods can be deposited fromtheir synthesis solution and employed as the active material in field-effecttransistor devices. Here, it was revealed that the as-fabricated nanorods canfeature an impressive electron mobility of 1.0 cm2 V-1 s-1, which is on par withthe performance of a work horse in the transistor field, viz. vacuumdeposited amorphous Si. We further demonstrated that the processability ofthe nanorods can be improved by a tuned light-exposure treatment, duringwhich the nanorod shell is polymerized while the high-mobility interior bulkis left intact. This has the desired consequence that stabile nanoroddispersions can be prepared in a wide range of solvents, and we anticipatethat functional electronic devices based on solution-processable nanorodscan be realized in a near future.

Organic electronics based on π-conjugated semi-conductor raises new technology, such as organic film transistors, e-paper, and organic photovoltaic cells that can be implemented cost-effectively on large-area applications. Currently, the device performance is limited by low charge carrier mobility. Poly(3-hexylthiophene) (P3HT) and organic field effect transistors (OFET) is used as a model to investigate morphology of the organic film and corresponding electronic properties. In this thesis, processing parameters such as boiling points and solubility are controlled to impact the micro- and macro-morphology of the film to enhance the charge transport of the device. Alternative approach to improve ordering of polymer chains and increase in charge transport without post-treatment of P3HT solution is studied. The addition of high boiling good solvent to the relatively low boiling main solvent forms ordered packing of π-conjugated polymers during the deposition process. We show that addition of 1% of dichlorobenzene (DCB) to the chloroform based P3HT solution was sufficient to improve wetting and molecular structures of the film to increase carrier mobility. Systematic study of solvent-assisted re-annealing technique, which has potential application in OFET encapsulation and fabrication of top-contact OFET, is conducted to improve mobility of OFET, and, to suggest a cost-effective processing condition suitable for industrial application. Three process parameters: boiling point, polarity, and solubility are investigated to further understand the trend of film response to the solvent-assisted technique. We report the high boiling non-polar solvents with relatively high RED values promote highest improvement in molecular packing and formulate crystalline structure of the thin film, which increases the device performance.

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.

Un des enjeux principaux de l’électronique organique est le développement de circuits associant des transistors organiques à effet de champ (OFETs) de type p et de type n stables à l’air ainsi que leur fabrication par voie liquide. Si de nombreux matériaux de type p existent, les exemples de matériaux de type n stables sont plus rares. L’objectif de ce travail de thèse a ainsi été de concevoir, de synthétiser, et de caractériser de nouvelles molécules π-conjuguées électrodéficientes solubles afin de les intégrer dans des transistors organiques à effet de champ de type n (OFETs) stables à l’air. Dans ce but, le coeur aromatique d’un pigment reconnu très stable chimiquement, la triphénodioxazine (TPDO), a été fonctionnalisé avec des fonctions solubilisantes et des groupements électroattracteurs pour moduler ses propriétés de solubilité et augmenter son affinité électronique. Les nombreuses variations structurales réalisées ont conduit à une famille complète de dérivés électrodéficients. Les nouveaux composés, caractérisés à l’état liquide et solide, ont été intégrés dans des OFETs et ont démontré, pour la plupart, un transport de charges négatives efficace. Au-delà de la rationalisation des résultats obtenus lors des synthèses, des caractérisations des matériaux et des performances des dispositifs électroniques, un dérivé tétracyané a rempli l'ensemble du cahier des charges initial (solubilité, mobilité de type n, stabilité à l’air), ce qui valide la démarche adoptée. / One the main challenges of organic electronics is the fabrication of electronic circuits combining p-type and n-type organic field effect transistors which can be processed by liquid route and are stable in air. Even though many efficient p-type organic materials have been reported, the examples of n-type analogues are rare. The aim of this PhD research work was therefore to design, synthesize and characterize new soluble and electron-acceptor π-conjugated molecules and determine their ability to transport electrons in organic field effect transistors (OFETs) under air. In this aim, the aromatic core of a well-known stable pigment, the Triphenodioxazine (TPDO), was functionalized with solubilizing groups and electron-withdrawing functions to tune the solubility and to yield a higher electron affinity. The various structural modifications achieved provided a complete family of electro-deficient materials. The new compounds were characterized in liquid and solid state, and then integrated in OFETs. Most of them led to an efficient negative charge carrier transport. Hereafter of the rationalization of the results during synthesis, characterization of new materials and physical characterizations of devices, a tetracyano derivative has fulfilled the initial project specifications in terms of solubility, electron mobility and air stability of the performances

This thesis deals with the synthesis of electroactiveorganic compounds. The synthesis of ethylenedioxy-benzodioxinstri-dioxin and tetra-dioxin are described. These molecules wereprepared with the aim of creating donor molecules for cationicradical salts. The symmetric analogs of tri-dioxin,methylenedioxy-derivative and ethylenedioxy-naphthalene werealso synthesized. Three different cation radical salts with 2:1stoichiometries were obtained from tri-dioxin, whiletetra-dioxin merely provided polycrystalline materials.Tri-dioxin and tetra-dioxin were also successful as operationalmatrixes in PALDI-TOF. Tetrathiafulvalenes with the2-dialkyl-amino-1,3-dithiolium-4-thiolate mesoion asbuilding-block was also synthesized. A series of doublyalkylthiol-substituted TTFs were prepared with the aim offorming self-assembly monolayers on gold surfaces in theapplication of organic thin film field-effect transistors.Film-formation for two TTFs were studied and they providedrelatively dense packed monolayers with a discrete distance ofthe TTF moiety from the gold surface. The mesoionic compound was also for the first time used inanumpolungreaction. The electrophile obtained in situ bytreatment of mesoion with sulfuryl chloride was reacted with avariety of electron-rich aromatic compounds. From the receivedproducts three new arylthio-substituted TTFs weresynthesized. <b>Keywords:</b>Synthesis, Benzodioxin, Tetrathiafulvalene,Mesoion, Organic Conductor, Cation Radical Salt, CyclicVoltammetry, Electrocrystallization, Self-Assembly Monolayer,SAM, Organic Field-Effect Transistor, OFET