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The organic electronics research field has advanced tremendously in the last decades, already rendering semiconductors able to compete with their inorganic counterparts. However, the final blossoming of this field would probably come with the complete understanding of the charge transport mechanism in organic materials. For this end, spectroscopies techniques have been proven to be of great interest in the elucidation of the different processes taking place in electronic devices. These techniques, and in particular Raman spectroscopy is a rapid, noninvasive technique able to gather information on molecular and supramolecular levels, thus being really useful for this purpose. In this talk, some examples from our research group will be presented in which several spectroscopic techniques, supported by DFT quantum chemical calculations have been used to shed light on the charge transport mechanisms in organic field effect transistors (OFETs). Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

The synthesis of 4-phenyl-4H-arsolo[2,3-d:5,4-d′]bis(thiazole) is reported, and its properties are compared to those of the previously prepared phosphole analogue. By comparison of their single-crystal structures, the harmonic oscillator model of heterocyclic electron delocalization (HOMHED) was used to directly compare the aromatic character of the two systems. The findings demonstrate that, although both compounds can be considered aromatic, the phosphole-containing compound had a greater degree of aromatic character than its arsole analogue. The arsole derivative exhibited excellent stability in ambient air with no formation of the arsole oxide observed upon storage. The absorption and photoluminescence spectra of the arsole derivate were subtly altered in comparison to the phosphole derivative, suggesting that changing pnictogenic atoms in such fused-ring systems to heavier analogues could be a viable way of tuning both the ambient stability and optoelectronic properties of such materials.

Electrochemically deposited polymers, also called “synthetic metals”, have emerged as potential candidates for chemical sensing due to their interesting and tunable chemical, electrical, and structural properties. In particular, most of these polymers (including polypyrrole, polyaniline, polythiophene) and their derivatives can be used as the sensitive layer of conductimetric gas sensors because of their conducting properties. An important advantage of polymer-based gas sensors is their efficiency at room temperature. This characteristic is interesting since most of the commercially-available sensors, usually based on metal oxides, work at high temperatures (300–400 °C). Consequently, polymer-based gas sensors are playing a growing role in the improvement of public health and environment control because they can lead to gas sensors operating with rapid detection, high sensitivity, small size, and specificity in atmospheric conditions. In this review, the recent advances in electrodeposited polymer-based gas sensors are summarized and discussed. It is shown that the sensing characteristics of electrodeposited polymers can be improved by chemical functionalization, nanostructuration, or mixing with other functional materials to form composites or hybrid materials.

Pi-conjugated biradical compounds become essential building blocks in DCC (dynamic covalent chemistry).1 This field is based on the creation of structural scaffolds based on chemical components which interact through strong but reversible bonds. Importantly, dynamic covalent bonds will be at the center of attention because of their unique feature to become reversible under mild conditions.2 Recently, we have demonstrated the reversible interconversion between a stable quinoid precursor based on a para-substituted carbazole with terminal dicyanomethylene groups and a macrocycle cyclophane upon soft external stimuli (temperature, pressure, light), which results on strong chromic features.3 In this work, we investigate the impact of the substitution pattern (i.e., the insertion of dicyanomethylene groups at the 2,7 (para) or 3,6 (meta) positions or the elongation of the carbazole backbone) on the formation of stimuli-responsive cyclophanes by self-assembly. To this end, we use a combined experimental and theoretical study that links vibrational spectroscopy (Raman and IR) with DFT calculations. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

In recent years, organic semiconducting materials have enabled technological innovation in the field of flexible electronics. Substantial optimization and development of new π-conjugated materials has resulted in the demonstration of several practical devices, particularly in displays and photoreceptors. However, applications of organic semiconductors in bipolar junction devices, e.g. rectifiers and inverters, are limited due to an imbalance in charge transport. The performance of p-channel organic semiconducting materials exceeds that of electron transport. In addition, electron transport in π-conjugated materials exhibits poorer atmospheric stability and dispersive transient photocurrents due to extrinsic carrier trapping. Thus development of air stable n-channel conjugated materials is required. New classes of materials with delocalized n-doped states are under development, aiming at improvement of the electron transport properties of organic semiconductors. In this review, we highlight the basic tenets related to the stability of n-channel organic semiconductors, primarily focusing on the thermodynamic stability of anions and summarizing the recent progress in the development of air stable electron transporting organic semiconductors. Molecular design strategies are analysed with theoretical investigations.

During this thesis, model donor-acceptor (DA) systems for organic photovoltaics have been studied by non-contact atomic force microscopy (nc-AFM) and Kelvin probe force microscopy (KPFM). To enhance the understanding of the optoelectronic processes on the nanoscale, DA systems with better defined structural and electronic properties than the one of most bulk heterojunction blends (BHJ), have been studied.With DA phase-separations of below 10nm in organic photovoltaic systems, the highest possible resolution has to be achieved by KPFM to investigate optoelectronic processes. It has been shown that nc-AFM/KPFM measurements in the regime of short range (SR) forces can increase imaging resolution. In preparation of such investigations, the influence of the interaction regime on the to- pographic measurement via KPFM has been studied for a self-assembly of P3DDT on HOPG. It is demonstrated that imaging in the SR-regime not only increases the lateral resolution, but also assures correct topographic height values.In a next step, DA blends of FG1:[70]PCMB have been studied by KPFM. For these BHJs, the structure and the scale of the DA phase-separation can be tuned via the liquid crystal behavior of the donor FG1. The in dark potential contrasts are consistent with surface and bulk morphology. The relationship between the surface photovoltage (SPV) and the tip-sample interaction regime has been analyzed. Increased SPV resolutions and image contrasts are obtained in the SR-regime. Furthermore, due to an optical field exaltation caused by the AFM tip, an amplified SPV signal is observed at small tip-sample distances.Finally, a new generation of DA dyads with donor and acceptor moieties has been studied. Its self-assembly on HOPG has been determined via a comparative study by scanning tunneling microscopy and nc-AFM plus molecular mechanics and dynamics simulations. By KPFM the charge carrier generation and collection has been analyzed down to the level of a single molecular layer. A clear relationship between the dyads' molecular assembly and their photovoltaic properties can be established.; Pour cette thèse, des systèmes donneur-accepteur (DA) modèles pour le photovoltaique organique ont été étudiés par microscopie à force atomique en mode non contact (nc-AFM) et microscopie à sonde de Kelvin (KPFM). Ces systèmes DA présentent une structure et des propriétés électroniques mieux controlées que dans la plupart des hétérojonctions DA en volume.Afin, d'étudier les propriétés optoélectroniques d'architectures DA présentant une séparation de phase à l'échelle de la dizaine de nanomètres, il est indispensable d'optimiser la résolution des modes nc-AFM/KPFM. Dans ce travail, l'influence du régime d'interaction pointe-surface sur les mesures a été étudiée dans le cas d'auto-assemblages de P3DDT sur substrat HOPG. Nous avons ainsi d ́emontré que l'imagerie dans le régime d'interaction à courte portée améliore non seulement la résolution latérale, mais permet également de réaliser des mesures de hauteur plus réalistes.Ensuite, un syst`eme DA à base de FG1:[70]PCBM a été étudié. Pour ce mélange DA, la nanostructure et l'échelle de la séparation de phase peuvent etre ajustées grace aux propriétés cristal liquide du composé donneur FG1. Les potentiels mesurés dans le noir sont consistants avec la morphologie attendue en surface et en volume. La relation entre le photo-potentiel de surface (SPV) et le régime d'interaction pointe-surface a pu etre précisément analys ́ee. Une meilleure résolution et un meilleur contraste des images SPV sont obtenus dans le régime à courte portée. De plus, à cause d'une exaltation du champ optique causée par la pointe, un signal SPV amplifié est mesuré pour des petites distances pointe-surface.Enfin, une nouvelle génération de diades comprenant des groupements donneur et accepteur a été étudiée. La nature de l'auto-assemblage sur HOPG a été établie sur la base d'études comparatives de microscopie à effet tunnel et de nc-AFM, avec le support de simulations en mécanique et dynamique moléculaire. Les mesures de photo-potentiel de surface ont ensuite permis de démontrer qu'il était possible d'étudier les mécanismes de photo-génération des porteurs jusqu'à l'échelle de la mono-couche moléculaire.

Phenylene-thiophene oligomers bearing peracetylated beta-D-glucose or N-BOC-L-phenylalanine as chiral substituents were synthesized in good yields by a versatile protocol based on the Suzuki-Miyaura cross-coupling reaction. Aryl iodides bearing the chiral biomolecules as substituents efficiently reacted with pinacol boronates of bi- or terthiophenes leading to the bio-functionalized oligomers in good yields. (C) 2010 Elsevier Ltd. All rights reserved.

The expected limits of silicon-based microelectronics in the coming years, have promoted the development of alternative solutions. Among them, organic electronics, using pi-conjugated organic materials as the active part of components, sounds very attractive. Increases observed the past 20 years in the performances of organic devices, find for a great part their origin in a better structure of the active film and the understanding of the relationship between structure and electronic properties in these materials still appears as a keynote for organic electronics.An STM structural study of self-assembled monolayers of either small molecules synthesised at the laboratory or polythiophenes was carried out in a first time to bring out self-assembly mechanisms. For the polymer monolayers, crystalline properties could be considerably improved with annealing of the sample. An organised second layer was observed for the first time on sample with higher coverage. Finally the influence of local inter or intra-chain conformation on polymer electronic properties was investigated by two-dimensional scanning tunnelling spectroscopy. Although the electronic structure of the polymer seems unaffected by intra-chain defect such as folds, an increase of the bandgap was observed above isolated chains of the second layer. This is rather surprising as such chains are generally assumed to be pi-stacked on the first layer, which should cause a partial closure of the bandgap.; La perspective d'atteindre prochainement les limites de la microélectronique à base de silicium a encouragé le développement de solutions alternatives. Parmi elles, l'électronique organique, dans laquelle les éléments actifs du composant sont constitués de systèmes organiques pi-conjugués, semble très prometteuse. Les progrès réalisés ces 20 dernières années sur les performances des dispositifs organiques résultent en grande partie de l'amélioration de la structuration de ces matériaux, et la relation entre structure et propriétés électroniques reste à ce jour l'une des problématiques majeures de l'électronique organique.Une caractérisation structurelle par STM de monocouches auto-assemblées réalisées à base de petites molécules synthétisées au laboratoire (B4OTF et B5OTF) ou de polythiophènes, a été entreprise dans un premier temps afin de dégager les mécanismes régissant l'assemblage des molécules. Dans le cas du polymère, une nette amélioration des propriétés cristallines a pu être obtenue par recuit des échantillons et une deuxième couche structurée a pu être observée pour la première fois sur des échantillons plus concentrés. Enfin l'influence de conformations locales inter ou intra-chaîne du polymère sur ses propriétés électronique intrinsèques a été investiguée par spectroscopie tunnel bidimensionnelle. S'il semble que les défauts intra-chaîne tels que les repliements aient peu d'impact sur la structure électronique du matériau, un surprenant accroissement du gap a été observé sur des chaînes isolées de deuxième couche qu'on suppose généralement en configuration de pi-stacking et donc susceptibles d'expérimenter une plus grande délocalisation électronique.

The expected limits of silicon-based microelectronics in the coming years, have promoted the development of alternative solutions. Among them, organic electronics, using pi-conjugated organic materials as the active part of components, sounds very attractive. Increases observed the past 20 years in the performances of organic devices, find for a great part their origin in a better structure of the active film and the understanding of the relationship between structure and electronic properties in these materials still appears as a keynote for organic electronics.An STM structural study of self-assembled monolayers of either small molecules synthesised at the laboratory or polythiophenes was carried out in a first time to bring out self-assembly mechanisms. For the polymer monolayers, crystalline properties could be considerably improved with annealing of the sample. An organised second layer was observed for the first time on sample with higher coverage. Finally the influence of local inter or intra-chain conformation on polymer electronic properties was investigated by two-dimensional scanning tunnelling spectroscopy. Although the electronic structure of the polymer seems unaffected by intra-chain defect such as folds, an increase of the bandgap was observed above isolated chains of the second layer. This is rather surprising as such chains are generally assumed to be pi-stacked on the first layer, which should cause a partial closure of the bandgap.; La perspective d'atteindre prochainement les limites de la microélectronique à base de silicium a encouragé le développement de solutions alternatives. Parmi elles, l'électronique organique, dans laquelle les éléments actifs du composant sont constitués de systèmes organiques pi-conjugués, semble très prometteuse. Les progrès réalisés ces 20 dernières années sur les performances des dispositifs organiques résultent en grande partie de l'amélioration de la structuration de ces matériaux, et la relation entre structure et propriétés électroniques reste à ce jour l'une des problématiques majeures de l'électronique organique.Une caractérisation structurelle par STM de monocouches auto-assemblées réalisées à base de petites molécules synthétisées au laboratoire (B4OTF et B5OTF) ou de polythiophènes, a été entreprise dans un premier temps afin de dégager les mécanismes régissant l'assemblage des molécules. Dans le cas du polymère, une nette amélioration des propriétés cristallines a pu être obtenue par recuit des échantillons et une deuxième couche structurée a pu être observée pour la première fois sur des échantillons plus concentrés. Enfin l'influence de conformations locales inter ou intra-chaîne du polymère sur ses propriétés électronique intrinsèques a été investiguée par spectroscopie tunnel bidimensionnelle. S'il semble que les défauts intra-chaîne tels que les repliements aient peu d'impact sur la structure électronique du matériau, un surprenant accroissement du gap a été observé sur des chaînes isolées de deuxième couche qu'on suppose généralement en configuration de pi-stacking et donc susceptibles d'expérimenter une plus grande délocalisation électronique.

Two unsymmetrical Zn (II) phthalocyanines 1 and 2 bearing an anchoring carboxylic function linked to the phthalocyanine ring through different rigid arylenevinylene bridges have been designed for dye-sensitized solar cell (DSSC) applications. The phthalocyanines 1 and 2, when anchored onto nanocrystalline TiO 2 films, yielded 30% incident monochromatic photon-to-current conversion efficiency (IPCE) and 2% power conversion efficiencies under AM1.5 sun.