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Le developpement des transistors a effet de champ organiques est limite par les performances des semi-conducteurs organiques disponibles sur le marche, la mobilite des charges electriques (mu) atteinte de maniere reproductible est de 1cm2/Vs. Un des principaux frein est la presence de defauts lies a l'organisation moleculaire. Les oligothiophenes sont a l'heure actuelle parmis les semi-conducteurs organiques les plus performants, c'est pourquoi nous avons decide de baser notre recherche sur des derives du terthiophenes et du quaterthiophene. Ces composes s'organisent de maniere a permettre une conduction a deux dimensions. Mais la mobilite de charge est limitee par des defauts de plan au sein du reseau moleculairemais aussi aux defauts dus aux irregularite de l'interface dielectrique/semi-conducteur. Afin de remedier a ce probleme, nous avons envisage deux approche: l'une pour la diminution des defauts de plan par l'utilisation de phase cristal liquides; l'autre vise la diminution des defauts dus aux irregularites de la surface du substrat, par l'utilisation de systemes pi relies par un pont covalent. Les 5,5'-dialkylterthiophenes (chaines allant du propyle au dodecyle) et le 5,5'- dihexylquaterthiophene sont conus pour former des phases cristal liquides. Mais ces dernieres n'apparaissent cependant qu'a des temperatures superieures a 45degC. LEs chaines alkyles utilisees etant toutes des chaines lineaires, notre premiere idee a ete de synthetiser de nouveaux derives avec des chaines alkyles ou alkenyles branchees. Une voie de synthese 'one-pot' permettant de varier aisement les chaines alkyles greffees dans les positions alfa et beta des bi-, ter- et quaterthiophene a ete mise au point. La reaction d'alkylation se fait en presence de n-BuLi et t-BuOK avec des rendements variant entre 80 et 90%. LEs composes obtenus par cette methode ne presentent pas les proprietes requises, c'est pourquoi une nouvelle modification structurale a ete envisagee: la dyssymetrisation. Cette fois les chaines greffees sur les positions alfa et beta sont differentes. De nouvelles voies de synthese ont ete etablies dans ce but. Elles sont basees sur l'heterocouplage de Suzuki qui va permettre la formation d'un lien carbone-carbone entre deux unites oligothiophenes. Ce couplage donne des rendements compris entre 35 et 65%. Notre connaissance de la formation de comnposes dissymetriques va etre directement appliquee a la formation des unites oligothiophenes reliees par un pont covalent. Quelque soit la nature du pont, il est necessaire de passer par un oligothiophene subtsitue en position alfa et pas omega. Deux types de ponts covalents ont ete utilises, un pont etylene et un pont disulfure, ce qui a requis la mise au point de deux schemas de synthese differents. POur les composes possendant un pont ethylene, un des synthon comporte deja un pont, l'etape finale consiste en un couplage de Suzuki. En ce qui concerne les derives possedant un pont sulfure, la formation du pont se fait lors de la derniere etape. Les proprietes thermotropes de tous les composes synthetises ont ete mesurees, cela nous a permis de faire une etude comparative dans le but de relier la structure aux proprietes thermotropes. La taille du corps aromatique, la longueur des chaines alkyles, la presence de branchements, d'insaturations sur les chaines laterales, de meme que la dissymetrisation ont ete etudies. Nous avons tentes de correler l'evolution des proprites thermotropes de nos composes avec l'evolution des temperatures de fusion des alcanes et alcenes correspondant. Cela donne de bons resultats pour les derives du terthiophenes, mais l'augmentation de la taille du corps aromatique complique fortement les resultats, LEs constatations les plus importantes sont que la presence de branchements sur les chaines alkyles provoque la diminution des temperatures de transistions des terthiophenes et des quaterthiophenes. Meme si en plus, ces branchements provoquent la perte du caractere fluide pour les terthiophenes. Il est incontestable que la methode qui permet de modifier de facon plus fine les temperatures de transition est la dissymetrisation. Cela nous permet d'obtenir des composes possedant les proprietes rechercheesa a savoir une phase cristal liquide a temperature ambiante. Sans toutefois comprendre le lien subtil entre la structure moleculaire et les proprietes thermotropes. Afin de comprendre les proprietes de semi-conduction des composes synthetises, nous avons fabriques des transistors a effet de champ avec trois d'entre eux; le 5,5'-dihexylquaterthiophene sert de compose modele, un derive du quaterthiophene possedant une phase cristal liquide a temperature ambiante et derive compose de deux unites hexylquaterthiophene relies par un pont ethylene. Les resultats pour le compose presentant une phase cristal liquide sont peu concluants. IL ne montre aucune proprietes de semi-conduction, ce qui peut s'expliquer par la difference de longueur des chaines alkyles greffees , qui induit un deplacement lateral defavorable au transport de charges. Pour le compose ponte une mobilite de charge de 0.015cm2/V.s. a ete mesuree ( compose de reference 0.013 cm2/V.s.) avec un dielectrique de rugosite nulle. Nous pouvons conclure que le compose ponte possede bien les proprietes de semi-conduction desirees.

Diimine rhenium(I) tricarbonyl complexes are known as phosphorescent emitters and electro- and photocatalysts for the reduction of CO₂ to CO. Conducting metallopolymers containing this rhenium(I) moiety should not only retain the photoluminescent and catalytic properties of the complex but also gain the conductivity, processability, and mechanical flexibility typical of [pi]-conjugated polymers. A series of tricarbonyl rhenium(I) diimine-type monomers and metallopolymers have been prepared. Appended to the ligands are thiophene and 3,4-ethylenedioxythiophene (EDOT) groups for electropolymerization of the metal complexes. UV-Vis absorption and emission spectroscopy studies of the monomers indicate that light emission originates from triplet ligand-centered (³LC) [pi] [right arrow] [pi]* and triplet metal-to-ligand charge transfer (³MLCT) excited states. Additionally, both the monomers and metallopolymers show electrocatalytic activity towards the reduction of CO₂ to CO. Furthermore, the EDOT-functionalized diimine-type ligand (EDOT₂-BPP) also serves as a good sensitizing ligand for luminescent lanthanide emission. A series of lanthanide complexes that utilize tris([beta]-diketonates) and EDOT₂-BPP ligands have been synthesized and studied using X-ray crystallography and photophysical techniques. Large quantum yields and microsecond lifetimes were found for the EuIII and SmIII complexes. Complexes of TbIII were found to have weak luminescent emission due to the less-than-optimal energy gap between the sensitizing ligands and the excited state of the TbIII ion. Oligothiophenes are models for polymeric systems because of solution processability, controlled chain length, and a well-defined structure. We have synthesized a library of alkyl and polyfluoroalkyl-substituted oligothiophenes to study how molecular structure, long-range order, spatial orientation, and varying degree of electronic coupling between molecules influences charge separation in photovoltaics. These oligoalkylthiophenes have been characterized by X-ray diffraction, photophysical methods, electrochemistry, and UV-Vis and EPR spectroscopies. Although the electronic properties of these oligoalkylthiophenes do not vary with alkyl group, aggregates of oligooctylthiophene, made through solution processing, have distinct morphologies with varying amounts of electronic disorder. The extent of electronic disorder within the aggregate is determined by comparing the suppression of the 0-0 vibronic band in the fluorescence spectra to that of the non-aggregated parent molecule. This extent of electronic disorder was correlated with the local contact potential of individual aggregates through Kelvin probe force microscopy (KPFM) measurements. / text

<p>This thesis deals with synthesis and characterization of newoligothiophenes and derivatives thereof, for use as organicsemiconductors in optical and electronic applications, such asfield-effect transistors and light-emitting diodes. Much workis devoted to the development of new synthetic strategies forinteresting building blocks, to beused for synthesizing suchmaterials. One series of regio-defined oligothiophenes, up tothe octamer, has been prepared and evaluated. Photoluminescencequantum efficiencies of these were 22-31 % in solution, butdropped to 2-5 % in the solid state. Another project deals withthe development of oligothiophenes with in-chain chirality.These may find use in polarized lightemitting diodes. Finally,two oligothienyl-substituted porphyrins have been synthesizedand are currently evaluated for use in light-emitting diodesand possibly in solar cells.</p>

This thesis targets the development of conjugated polymers with improved process ability from solutions. Two types of ionic polymers are addressed: (i) conjugated metallo-supramolecular polymers (MSPs) composed of conjugated heteroaromatic unimers (building blocks) linked to chains by various metal ions giving charged main chains, and (ii) polythiophene polyelectrolytes containing ionic pendants. Processing advantages of conjugated polyelectrolytes consist in the possibility of their processing from solutions in green solvents such as alcohols or even water. The advantages of MSPs consist in the thermodynamic control of the degree of polymerization (length) of their chains in solutions by the choice of solvent and temperature. As a result, MSPs reversibly provide systems of low viscosity that can be processed from solutions more easily than high-molar-mass polymers giving highly viscous solutions. Synthesis of appropriately designed unimer(s) is the key step of preparation of an MSP. Within this thesis, a series of novel unimers composed of linear oligothiophene type (mono-, bi-, ter- a thieno-thiophene- diyl) central blocks capped with 2,6-bis(oxazoline-2-yl)pyridine (pybox) or 2,6-bis(imidazole-2-...

This thesis deals with synthesis and characterization of newoligothiophenes and derivatives thereof, for use as organicsemiconductors in optical and electronic applications, such asfield-effect transistors and light-emitting diodes. Much workis devoted to the development of new synthetic strategies forinteresting building blocks, to beused for synthesizing suchmaterials. One series of regio-defined oligothiophenes, up tothe octamer, has been prepared and evaluated. Photoluminescencequantum efficiencies of these were 22-31 % in solution, butdropped to 2-5 % in the solid state. Another project deals withthe development of oligothiophenes with in-chain chirality.These may find use in polarized lightemitting diodes. Finally,two oligothienyl-substituted porphyrins have been synthesizedand are currently evaluated for use in light-emitting diodesand possibly in solar cells. / NR 20140805

Electronic structure calculation is an essential approach for determining the structure and function of molecules and is therefore of critical interest to physics, chemistry, and materials science. Of the various algorithms for calculating electronic structure, the pseudospectral method is among the fastest. However, the trade-off for its speed is more up-front programming and testing, and as a result, applications using the pseudospectral method currently lag behind those using other methods. In Part I of this dissertation, we first advance the pseudospectral method by optimizing it for an important application, polarized Raman spectroscopy, which is a well-established tool used to characterize molecular properties. This is an application of particular importance because often the easiest and most economical way to obtain the polarized Raman spectrum of a material is to simulate it; thus, utilization of the pseudospectral method for this purpose will accelerate progress in the determination of molecular properties. We demonstrate that our implementation of Raman spectroscopy using the pseudospectral method results in spectra that are just as accurate as those calculated using the traditional analytic method, and in the process, we derive the most comprehensive formulation to date of polarized Raman intensity formulas, applicable to both crystalline and isotropic systems. Next, we apply our implementation to determine the orientations of crystalline oligothiophenes --- a class of materials important in the field of organic electronics --- achieving excellent agreement with experiment and demonstrating the general utility of polarized Raman spectroscopy for the determination of crystal orientation. In addition, we derive from first-principles a method for using polarized Raman spectra to establish unambiguously whether a uniform region of a material is crystalline or isotropic. Finally, we introduce free, open-source software that allows a user to determine any of a number of polarized Raman properties of a sample given common output from electronic structure calculations. In Part II, we apply the pseudospectral method to other areas of scientific importance requiring a deeper understanding of molecular structure and function. First, we use it to accurately determine the frequencies of vibrational tags on biomolecules that can be detected in real-time using stimulated Raman spectroscopy. Next, we evaluate the performance of the pseudospectral method for calculating excited-state energies and energy gradients of large molecules --- another new application of the pseudospectral method --- showing that the calculations run much more quickly than those using the analytic method. Finally, we use the pseudospectral method to simulate the bottleneck process of a solar cell used for water splitting, a promising technology for converting the sun's energy into hydrogen fuel. We apply the speed of the pseudospectral method by modeling the relevant part of the system as a large, explicitly passivated titanium dioxide nanoparticle and simulating it realistically using hybrid density functional theory with an implicit solvent model, yielding insight into the physical nature of the rate-limiting step of water splitting. These results further validate the particularly fast and accurate simulation methodologies used, opening the door to efficient and realistic cluster-based, fully quantum-mechanical simulations of the bottleneck process of a promising technology for clean solar energy conversion. Taken together, we show how both polarized Raman spectroscopy and the pseudospectral method are effective tools for analyzing the structure and function of important molecular systems.

Small fluorescent probes are important tools when studying protein aggregates involved in different neurodegenerative diseases, such as Alzheimer’s disease. Luminescent conjugated oligothiophenes have been developed and shown to be excellent ligands when studying morphology among amyloids, due to their conjugated thiophene backbone that provides them with unique photophysical properties. This kind of probes are being developed successively to enhance the specificity of their biological targets. In this project, luminescent conjugated oligothiophenes functionalized with amino acids, so called proteophenes, have been synthesized to investigate their optical properties. Since amino acids are chiral molecules, the possibility of induced chirality to the thiophene backbone was examined, as well as the proteophenes ability to work as amyloidospecific ligands for the study of protein aggregates. The synthesis of four different proteophenes are presented in this report, along with analysis results of their photophysical properties.

Le developpement des transistors a effet de champ organiques est limite par les performances des semi-conducteurs organiques disponibles sur le marche, la mobilite des charges electriques (mu) atteinte de maniere reproductible est de 1cm2/Vs. Un des principaux frein est la presence de defauts lies a l'organisation moleculaire. Les oligothiophenes sont a l'heure actuelle parmis les semi-conducteurs organiques les plus performants, c'est pourquoi nous avons decide de baser notre recherche sur des derives du terthiophenes et du quaterthiophene. Ces composes s'organisent de maniere a permettre une conduction a deux dimensions. Mais la mobilite de charge est limitee par des defauts de plan au sein du reseau moleculairemais aussi aux defauts dus aux irregularite de l'interface dielectrique/semi-conducteur.<p>Afin de remedier a ce probleme, nous avons envisage deux approche: l'une pour la diminution des defauts de plan par l'utilisation de phase cristal liquides; l'autre vise la diminution des defauts dus aux irregularites de la surface du substrat, par l'utilisation de systemes pi relies par un pont covalent.<p>Les 5,5'-dialkylterthiophenes (chaines allant du propyle au dodecyle) et le 5,5'- dihexylquaterthiophene sont conus pour former des phases cristal liquides. Mais ces dernieres n'apparaissent cependant qu'a des temperatures superieures a 45degC. LEs chaines alkyles utilisees etant toutes des chaines lineaires, notre premiere idee a ete de synthetiser de nouveaux derives avec des chaines alkyles ou alkenyles branchees. Une voie de synthese 'one-pot' permettant de varier aisement les chaines alkyles greffees dans les positions alfa et beta des bi-, ter- et quaterthiophene a ete mise au point. La reaction d'alkylation se fait en presence de n-BuLi et t-BuOK avec des rendements variant entre 80 et 90%. LEs composes obtenus par cette methode ne presentent pas les proprietes requises, c'est pourquoi une nouvelle modification structurale a ete envisagee: la dyssymetrisation. Cette fois les chaines greffees sur les positions alfa et beta sont differentes. De nouvelles voies de synthese ont ete etablies dans ce but. Elles sont basees sur l'heterocouplage de Suzuki qui va permettre la formation d'un lien carbone-carbone entre deux unites oligothiophenes. Ce couplage donne des rendements compris entre 35 et 65%. <p>Notre connaissance de la formation de comnposes dissymetriques va etre directement appliquee a la formation des unites oligothiophenes reliees par un pont covalent. Quelque soit la nature du pont, il est necessaire de passer par un oligothiophene subtsitue en position alfa et pas omega. Deux types de ponts covalents ont ete utilises, un pont etylene et un pont disulfure, ce qui a requis la mise au point de deux schemas de synthese differents. POur les composes possendant un pont ethylene, un des synthon comporte deja un pont, l'etape finale consiste en un couplage de Suzuki. En ce qui concerne les derives possedant un pont sulfure, la formation du pont se fait lors de la derniere etape. <p><p>Les proprietes thermotropes de tous les composes synthetises ont ete mesurees, cela nous a permis de faire une etude comparative dans le but de relier la structure aux proprietes thermotropes. La taille du corps aromatique, la longueur des chaines alkyles, la presence de branchements, d'insaturations sur les chaines laterales, de meme que la dissymetrisation ont ete etudies. Nous avons tentes de correler l'evolution des proprites thermotropes de nos composes avec l'evolution des temperatures de fusion des alcanes et alcenes correspondant. Cela donne de bons resultats pour les derives du terthiophenes, mais l'augmentation de la taille du corps aromatique complique fortement les resultats, LEs constatations les plus importantes sont que la presence de branchements sur les chaines alkyles provoque la diminution des temperatures de transistions des terthiophenes et des quaterthiophenes. Meme si en plus, ces branchements provoquent la perte du caractere fluide pour les terthiophenes. Il est incontestable que la methode qui permet de modifier de facon plus fine les temperatures de transition est la dissymetrisation. Cela nous permet d'obtenir des composes possedant les proprietes rechercheesa a savoir une phase cristal liquide a temperature ambiante. Sans toutefois comprendre le lien subtil entre la structure moleculaire et les proprietes thermotropes. <p>Afin de comprendre les proprietes de semi-conduction des composes synthetises, nous avons fabriques des transistors a effet de champ avec trois d'entre eux; le 5,5'-dihexylquaterthiophene sert de compose modele, un derive du quaterthiophene possedant une phase cristal liquide a temperature ambiante et derive compose de deux unites hexylquaterthiophene relies par un pont ethylene. Les resultats pour le compose presentant une phase cristal liquide sont peu concluants. IL ne montre aucune proprietes de semi-conduction, ce qui peut s'expliquer par la difference de longueur des chaines alkyles greffees ,qui induit un deplacement lateral defavorable au transport de charges. Pour le compose ponte une mobilite de charge de 0.015cm2/V.s. a ete mesuree ( compose de reference 0.013 cm2/V.s.) avec un dielectrique de rugosite nulle. Nous pouvons conclure que le compose ponte possede bien les proprietes de semi-conduction desirees. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

The present thesis is focused on rational design and synthesis of π-conjugated donoracceptor-donor (D-A-D) type oligomers and D-A type copolymers. Thesis is organized in seven chapters, apart from introduction remaining six chapters are grouped into two parts (A and B). Part A deals with Chapters 2, 3, 4 and Part B contains chapters 5, 6 and 7. A brief discussion on the content of individual chapters is provided below. Chapter 1 discusses the introduction to organic solar cell with operating principles and effect of spinodal decomposition on stability of the devices is presented. The status and literature related to the improvement of life time of the organic solar cells by self-assembly approach has been explored. In addition, design and synthesis of the fluorine substituted π-conjugated organic semiconductors for n-type OFETs and OLED has been discussed. Part A This part of the thesis attempt to address some of the challenges listed below (1) Investigation of miscibility of binary components in bulk heterojunction solar cells through H-bonding approach. (2) Synthesis of new low band gap molecular semiconductors having H-bonding sites. (3) Fabrication of bulk heterojunction solar cell devices using these new molecules and exploring the photovoltaics performance. Chapter 2, donor-acceptor-donor (D-A-D) concept has been employed to design low band gap oligomers named as TTB. Barbiturate functional group has been utilized to explore the concepts of supramolecular chemistry. It is shown that, TTB molecule self-organizes via intermolecular H-bonding between barbituric acid units. Interactions between the oligothiophene subunits were also found to be important, affording nanoribbons that were observed by atomic force and transmission electron microscopy. The applicability of TTB for organic electronic applications was investigated by fabricating organic field-effect transistors (OFETs) and organic photovoltaic device. The crystalline nanoribbons were beneficial in understanding the phase morphology of PCBM and TTB blend. Chapter 3, the self-assemble property of TTB was disrupted by the substitution of methyl group on the nitrogen of the barbituric acid moiety. The optical and electrochemical properties of the new derivative have been investigated by UV-Visible spectroscopy, photoluminescence spectroscopy and cyclic voltammetry. Further investigations on the effect of self-assembly on organic solar cells were carried out by fabricating BHJ and OFET. The results proved that the self-assembly within the donor moieties led to complete phase separation between the donor and acceptor which had an adverse effect on the photovoltaic performance. Chapter 4, the conjugation of TTB was extended by the synthesis of two new copolymers by polymerizing with two oliogothiophene (terthiophene and benzobithiophene) derivatives with different donating strength. The investigation of photophysical and electrochemical properties of copolymers were studied by varying the donating strength. As we increase the donating strength of oligothiophenes, the intramolecular charge transfer band of DA copolymers was red shifted. Further, density functional theory (DFT) calculation of these materials was carried out to get insight into their photophysical properties. Part B This part of the thesis attempt to address some of the challenges listed below (1) Investigation of fluorine substituted organic semiconductos like 2,2’ bithiazole and pheanthroimidazole. (2) Synthesis of pentafluoro phenyl appended derivatives of 2,2’ bithiazole and pheanthroimidazole. (3) Fabrication of OFETs and OLEDs using these new molecules and elucidated the device performance with molecular structure. Chapter 5, pentafluorophenyl appended 2,2’-bithiazole derivatives were synthesized. The single crystal x-ray diffraction studies shows the unusual strong type-II F•••F interactions within the distance of 2.668 Å, at an angle of 89.14° and 174.15°. It also shows the usual type-I F•••F interaction within the distance of 2.825Å, at an angle of 137.38° and 135.93°. Upon bromination type-II Br•••Br interaction was observed and the packing was further stabilized by S•••Br interactions. The conjugation was further extended with different aromatic and heteroaromatic substituents and synthesized the star shaped structure. The band gap as well as the electronic energy levels was tuned by substituting various aromatic and heteroaromatic substituents. These star shaped derivatives shows electron mobilities in the order of 10-4 to 10-3cm2/Vs. Chapter 6, Novel D-A copolymers were synthesized by Stille condensation of electron acceptor fluorinated phenanthroimidazole with electron donors like terthiophene and benzobithiophene. Prior to that insoluble pentafluoro phenyl phenanthroimidazole was Nalkylated in presence of DMF which concurrently resulted in C-F activation of the pentafluoro phenyl moiety. As we increase the donor strength from benzobithiophene to terthiophene the absorbance spectra was red shifted from 446 nm to 482 nm in solution and 455 nm to 484 nm in solid state. The band gap of these copolymers was found to be 2.4 eV for PIBDT and 2.2 eV for PIDHTT from the absorbance spectra. The photoluminescence data shows that these materials are promising for the yellow colour as well as orange colour displays, of narrow wavelength range (FWHM 40 nm for PIBDT and 35 nm for PIDHTT), which can be achieved just by the manipulation of donor moieties in the copolymers. The preliminary electroluminiscence data shows high brightness of 888cd/m2 (orange luminescence) for PIDHTT and 410cd/m2 (yellow luminescence) for PIBDT. Chapter 7, Acenaphtho[1,2-b]quinoxaline based donor–acceptor type low band gap conjugated copolymers were synthesized by Stille coupling reaction with the corresponding oligothiophene derivatives. The optical properties of the copolymers were characterized by ultraviolet-visible spectrometry while the electrochemical properties were determined by cyclic voltammetry. The band gap of these polymers was found to be in the range of 1.8-2.0 eV as calculated from the optical absorption band edge. The intense charge transfer band in absorption spectra shows the significant effect of acceptor in the copolymers. X-ray diffraction measurements show weak π–π stacking interactions between the polymer chains. The OFET devices fabricated using these co-polymers showed dominant p-channel transistor behavior with the highest mobility of 1×10-3cm2/Vs.