The successful realization of highly efficient bulk heterojunction OPV devices requires the development of organic donor and acceptor materials with tailored properties. Recently, non-fullerene acceptors (NFAs) have emerged as an alternative to the ubiquitously used fullerene derivatives. NFAs showed a rapid increase in efficiencies, now exceeding a PCE of 13%. In my thesis research, I used two small molecule IDT-based acceptors, namely O-IDTBR and O-IDTBCN, in combination with a wide bandgap donor polymer, GeNIDT-BT, as active material in BHJ solar cells and investigated their photophysical characteristics. The polymer combined with O-IDTBR as acceptor achieved a power conversion efficiency of only 2%, which is significantly lower than that obtained for the system of GeNIDT-BT: O-IDTBCN (5.3%). Using nano- to microsecond transient absorption spectroscopy, I investigated both systems and demonstrated that GeNIDT-BT:O-IDTBR exhibits more geminate recombination of interfacial charge-transfer states, leading to lower short circuit currents. Using time-delayed collection field experiments, I studied the field dependence of charge generation and its impact on the device fill factor. Overall, my results provide a qualitative understanding of the efficiency-limiting processes in both systems and their impact on device performance.

Organic solar cells (OSCs) have gained considerable attention from the scientific community in recent decades due to their remarkable power conversion efficiency (PCE), flexibility, and cost-effectiveness in producing large-area batteries. Despite the ongoing research efforts that have led to a PCE exceeding 19% for single-junction OSCs and surpassing 20% for multi-junction OSCs, the commercialization of these devices is hampered by their poor stability, reliance on specific additives, and the use of toxic solvents. To address these shortcomings, this study focuses on investigating the 3 * 3 thermosets matrix to facilitate the selection of precursors for in-situ crosslinking thermosets. Furthermore, in this study, we fabricated the devices using green solvents to narrow the gap between PCE and stability under environmentally friendly conditions. We utilized PTQ10: BTP-BO4Cl as the model system and employed tetrahydrofuran (THF) as an eco-friendly solvent. The research focused on examining the thermoset's glass transition temperature (Tg), modulus and morphology properties. The resulting cross-linked thermoset network has high-density hydrogen bonding and network grids, which helps to stabilize the morphology of the active layer. The findings indicated that selecting a thermoset with high Tg, high modulus (4-8 MPa), and good uniformity as an in-situ crosslinking additive would be beneficial. These results can guide the selection of universal in-situ crosslinking thermosets and aid in improving the stability of various organic electronic devices.

The longstanding belief that women are born with a finite ovarian reserve has been debated for over a decade, ever since the discovery, and subsequent isolation, of purported oogonial stem cells (OSCs) from adult mammalian ovaries. This rare cell population has now been reported in the mouse, rat, pig, rhesus macaque monkey and humans and, although a physiological role for the cells has not been proven, they do appear to generate oocytes when cultured in specific environments, resulting in live offspring in rodents. The primary aim of this thesis was to verify independently the existence of OSCs in human ovary and determine whether they could be isolated from a large animal model, the cow. The secondary aim was to investigate the cells’ in vitro potential, both to undergo neo-oogenesis and as a model for germ cell development. Putative bovine and human OSCs were isolated from disaggregated adult ovarian cortex using a previously validated fluorescence-activated cell sorting (FACS)-based technique, with cells sorted for externally expressed DDX4 (VASA). Freshly isolated and cultured cells were characterised by analysing their expression of pluripotency and germline markers, using RT-PCR, immunocytochemistry and Western blotting. The in vitro neo-oogenesis potential of the cells was explored by injecting fluorescently labelled cells into fragments of adult ovarian cortex and by forming aggregated artificial “ovaries” with putative OSCs and fetal ovarian somatic cells. Germ cell model experiments comprised treatment of cultured cells with BMP4 and/or retinoic acid (RA), with subsequent quantitative RT-PCR and immunocytochemistry analysis for downstream BMP4- and RA-response genes, and liposomal-mediated transfection of cells with a DAZL overexpression plasmid to assess their meiosis-related gene response. Scarce populations of putative OSCs were retrieved from 5 human samples (aged 13- 40 years) and 6 bovine samples. The cells were cultured long-term for up to 7 months and demonstrated consistent expression of several pluripotency-associated and germline markers at the mRNA and protein level, including LIN28, NANOG, POU5F1 (OCT4), IFITM3 (fragilis), STELLA, PRDM1 (BLIMP1), and C-KIT, indicating their early germline nature. Investigation of neo-oogenesis potential revealed that putative human OSCs were associated rarely with fetal somatic cells in primordial follicle-like structures, but could not be confirmed to have undergone oogenesis. However, like early germ cells, putative bovine and human OSCs were BMP4 and RA responsive, with both species demonstrating significant upregulation of expression of ID1 and bovine cells exhibiting a significant increase in MSX1, MSX2 and the meiotic marker SYCP3 in response to BMP4 and/or RA treatment. Cells could be successfully transfected to overexpress DAZL; however, no significant downstream gene expression changes were observed. This is the first report of putative bovine OSC isolation and corroborates a previous report showing putative human OSC isolation. Although the expression of both stem cell and germline markers indicates the cells have characteristics of OSCs, their capacity to enter meiosis and form functional oocytes has yet to be determined. Putative bovine OSCs, however, show promise as a novel model for investigating germ cell development. If their potential can be harnessed, then OSCs may have a role in clinical applications, for example in fertility preservation, in the future. Future experiments will examine the neo-oogenesis capabilities of the cells further and explore novel cell delivery systems for clinical use.

L'objectif de ce travail était le développement des nanocomposites d’EVOH/zeolites à base de charges telles que les zéolites pour l’encapsulation des cellules solaires organiques, et l’étude de leur comportement photochimique. Ce travail a porté sur l’étude du mécanisme de photooxydation des copolymères d’EVOH puis sur l'impact des zéolites sur ce mécanisme. Les propriétés fonctionnelles des nanocomposites d’EVOH/zéolites ont été étudiées en prenant en compte le taux de charge et la taille des particules. Les propriétés des copolymères d’EVOH et des nanocomposites d’EVOH/zéolites comme la transparence optique, la morphologie de surface, les propriétés mécaniques et thermiques, et les propriétés d'absorption de l'eau ont été étudiées. Sur la base des résultats obtenus, les meilleurs candidats pour l'encapsulation des cellules solaires organiques ont été proposés. Le mécanisme de photooxydation des copolymères a été proposé, la photostabilité des matériaux et l'impact des zéolites sur le comportement photochimique du polymère ont été étudiés. Le test électrique de calcium et le suivi des performances des cellules solaires organiques encapsulées ont été effectués afin d'évaluer l’efficacité des matériaux étudiés comme candidats potentiels pour une encapsulation efficace et stable des cellules solaires. / The goal of this work was to develop EVOH/zeolite nanocomposites based on inorganic fillers such as zeolites for potential encapsulation of OSCs and to investigate their photochemical behaviour. The research was focused on the photooxidation mechanism of pristine EVOH copolymers and on the impact of the filler addition on this mechanism. EVOH/zeolite nanocomposites functional properties were characterised taking into account different particle sizes and filler contents. Properties of EVOH copolymers and EVOH/zeolites nanocomposites such as optical transparency, surface morphology, mechanical and thermal properties, and water uptake properties were investigated. On the basis of obtained results, the best candidate(s) for encapsulation of organic solar cells has been proposed. The chemical degradation mechanism of pristine polymers has been proposed, the materials photostability and the impact of the zeolite particles on the photochemical behaviour of the polymer have been studied. Electrical calcium test and performance of encapsulated OSCs were carried out in order to evaluate the ability of the studied materials to be used as potential candidates for efficient and stable encapsulation coatings for OSCs applications.

Solution-processed organic field effect transistors (OFETs) have emerged in recent years as promising contenders to be part of electronic and optoelectronic circuits owing to their compatibility with low-cost high throughput roll-to-roll manufacturing technology. The stringent performance requirements for OFETs in terms of carrier mobility, switching speed, turn-on voltage and uniformity over large areas require the performance of single crystal-based OFETs, but these suffer from major scale-up challenges. To achieve device performance approaching that of single crystals with scalable, high throughput and industry-compatible solution coating of OFETs requires understanding and ultimately controlling the crystallization of organic semiconductors (OSCs), and producing very low defect-density thin films. In this thesis, we develop an understanding of the process-structure-property-performance relationship in OSCs that bring fresh insights into the nature of solution crystallization and lead to novel ways to control OSC crystallization, and finally help achieve fabrication of high-performance OFETs by scalable, high throughput and industry-compatible blade coating method. We probe the solution crystallization of OSCs by employing a suite of ex & in situ characterization techniques. This leads us to an important finding that OSC molecules aggregate to form a dense amorphous intermediate state and nucleation happens from this intermediate state during blade coating under a wide window of coating conditions. This phenomenon resembles the so-called two-step nucleation model. Two-step nucleation mediates the crystallization of a wide range of natural and synthetic products ranging from soft materials, such as proteins, biominerals, colloids and pharmaceutical molecules, to inorganic compounds. We go on to show that this nucleation mechanism is generally applicable to achieve formation of high-quality polycrystalline films in a variety of small molecule OSCs and their polymer blends. This phenomenon results in highly textured and well-connected domains, which exhibit reduced interfacial and bulk trap-state densities, helping raise the carrier mobility by one to two orders of magnitude in OFETs in comparison to direct nucleation. We extend the understanding developed for solution crystallization of various acenes and thiophene-based small molecule OSCs to the high-performance benzothieno-benzothiophene (BTBT) based small molecule OSCs. On this end, we develop protocols to fabricate high-quality thin films of BTBT based OSCs by blade coating at industrially compatible coating speeds (>100 mms-1). These films show massive single-domains with very few apparent defects when crystallized via multiple liquid-crystalline phases in two-step nucleation conditions, resulting in an average carrier mobility of ~10 cm2V-1s-1. To sum up, this thesis develops an understanding of OSC solution crystallization and efficient protocols to control polycrystalline thin film quality for high-performance OFETs. These protocols involve a combination of two-step nucleation pathway, solvent mixtures, polymer blends and device-manufacturing conditions. Our efforts enable to realize high-performance OFETs based on high-quality polycrystalline OSC thin films at industry-compatible conditions.

No description available.

A new dual-boron-cored luminogen ligated with a nitrogen-containing multidentate ligand and four bulky phenyl rings was readily synthesized. The unique molecular structure endows this BN-containing luminogen with rich photophysical properties in either solution or in the solid state, including a large Stokes shift, aggregation induced emission activity and reversible piezochromism. Furthermore, this BN-containing luminogen exhibits good capabilities for imaging living cells and sensing of fluoride anions.

Cette thèse est porté sur l'étude du transport électronique dans différents matériaux organiques semi-conducteurs, considérés comme candidats potentiels pour des applications en Electronique de Spin Organique. Pour rendre possible la diffusion d'un courant polarisée en spin à l'intérieur d'un semi-conducteur (injection-transport-détection), le mécanisme de transport et la mobilité des porteurs de charge, ainsi que la nature et la valeur de la résistance de contact de l'interface séparant matériau organique et électrodes métalliques ferromagnétiques, doivent répondre à des critères très stricts. Tous les dispositifs sont en géométrie latérale. Nous étudions trois matériaux organiques différents: des fibres supramoléculaires auto-assemblées, une encre de nana-flocons de graphene exfolié en phase liquide et un polymère semi-conducteur fortement dopé en forme de couche mince. Nos résultats montrent que les conditions sont partiellement respectées, mais que des défis demeurent. / In this thesis, we study the electronic charge transport properties in different high mobility organic semiconductors considered as possible candidates for applications in Organic Spintronics. Stringent conditions are needed to make possible the diffusive transport of a spin-polarized current through an organic spacer (injection-transport-detection): the mechanism of charge transport and the carriers mobility, as well as the interface between the organic semiconductor and the ferromagnetic metallic electrodes, should meet special criteria. Our devices are in lateral geometry. We investigate three organic materials, all compatible with wet processing of organic electronics: supramolecular fibers self-assembled by light irradiation, an ink of liquid-phase exfoliated graphene nano-sheets and a conjugated polymer semiconductor thin film exposed to strong electrochemical doping. We observe that the criteria are partially matched, but some challenges are still present.

L’attention portée sur la notion de “gouvernance” est expliqué pour être associé, dans cette thèse, au domaine de la coopération internationale pour le "développement". La “gouvernance”, dans ce sens, est compris comme un réseau d'interactions, à un ensemble d'acteurs et d'organisations, avec les relation qu'ils soient conformes à l'autre, marqué par des contradictions et des défis. C'est parce que la pratique de la coopération internationale pour le “développement” se produit dans des conditions asymétriques, dans lesquelles un groupe dominant d’acteurs a plus de pouvoir pour fixer des règles du jeu (HERMET, 2002; 2003; 2005; HERMET; KAZANCIGIL, 2005; NAVARRO-FLORES, 2007), ce qui potentialise l’apparition de conflits. Aussi le "développement", un terme profondément idéologisé, est une autre source de conflit sur le processus d'articulation des acteurs impliqués dans des actions de coopération internationale. Cette thèse vise à contribuer à la compréhension du modèle de gouvernance dominante dans la coopération Nord-Sud orientée pour le “développement”. Une étude de cas interprétative simple qui caractérise le type d'étude dans cette thèse. La méthode de recherche est composé des techniques de l’Analyse Interprétative ainsi que des méthodes comparative et d'observation. Comme résultats, les données de recherche indiquent, entre autres choses, une distribution centralisée des ressources, en se concentrant surtout sur les résultats et la diffusion des “bonnes pratiques”, un manque d’articulation entre les différents acteurs concernés, en particulier en matière de communication. En plus, la focalisation de l'attention est la dimension instrumentale du processus pour les acteurs stratégiques, sans égard à la dynamique et la spécificité du processus luimême. / A atenção colocada sobre a noção de “governança” é explicada na medida em que esta é associada, nesta tese, ao campo da cooperação internacional para o “desenvolvimento”. “Governança”, neste sentido, é compreendida como uma rede de interações, no sentido de um conjunto de atores e de organizações, juntamente com as relações que estes conformam entre si, pautada por contradições e desafios. Isto porque a prática da cooperação internacional para o “desenvolvimento” ocorre sob condições assimétricas, em que um grupo dominante de atores tem mais poder para definir as regras do jogo (HERMET, 2002; 2003; 2005; HERMET; KAZANCIGIL, 2005; NAVARRO-FLORES, 2007), o que potencializa a ocorrência de conflitos. Também o “desenvolvimento”, termo profundamente ideologizado, constitui outra fonte de conflito incidente sobre o processo de articulação dos atores em torno de ações de cooperação internacional. Esta tese tem por objetivo contribuir para a compreensão do modelo de governança dominante na cooperação Norte-Sul orientada para o “desenvolvimento”. Um estudo de caso interpretativo simples caracteriza o tipo de estudo desta tese, sendo o método de investigação composto por técnicas da Análise Interpretativa bem como pelos métodos de comparação e observação. Como resultados, os dados da pesquisa apontam, entre outros elementos, uma distribuição de recursos centralizada, com foco principal no resultado e na disseminação de “boas práticas”, uma carência de articulação entre os diversos atores implicados, sobretudo com relação à comunicação, além do foco de atenção ser a dimensão instrumental do processo por parte dos atores estratégicos, sem atentar para a dinâmica e para a especificidade do próprio processo.

L’attention portée sur la notion de “gouvernance” est expliqué pour être associé, dans cette thèse, au domaine de la coopération internationale pour le "développement". La “gouvernance”, dans ce sens, est compris comme un réseau d'interactions, à un ensemble d'acteurs et d'organisations, avec les relation qu'ils soient conformes à l'autre, marqué par des contradictions et des défis. C'est parce que la pratique de la coopération internationale pour le “développement” se produit dans des conditions asymétriques, dans lesquelles un groupe dominant d’acteurs a plus de pouvoir pour fixer des règles du jeu (HERMET, 2002; 2003; 2005; HERMET; KAZANCIGIL, 2005; NAVARRO-FLORES, 2007), ce qui potentialise l’apparition de conflits. Aussi le "développement", un terme profondément idéologisé, est une autre source de conflit sur le processus d'articulation des acteurs impliqués dans des actions de coopération internationale. Cette thèse vise à contribuer à la compréhension du modèle de gouvernance dominante dans la coopération Nord-Sud orientée pour le “développement”. Une étude de cas interprétative simple qui caractérise le type d'étude dans cette thèse. La méthode de recherche est composé des techniques de l’Analyse Interprétative ainsi que des méthodes comparative et d'observation. Comme résultats, les données de recherche indiquent, entre autres choses, une distribution centralisée des ressources, en se concentrant surtout sur les résultats et la diffusion des “bonnes pratiques”, un manque d’articulation entre les différents acteurs concernés, en particulier en matière de communication. En plus, la focalisation de l'attention est la dimension instrumentale du processus pour les acteurs stratégiques, sans égard à la dynamique et la spécificité du processus luimême. / A atenção colocada sobre a noção de “governança” é explicada na medida em que esta é associada, nesta tese, ao campo da cooperação internacional para o “desenvolvimento”. “Governança”, neste sentido, é compreendida como uma rede de interações, no sentido de um conjunto de atores e de organizações, juntamente com as relações que estes conformam entre si, pautada por contradições e desafios. Isto porque a prática da cooperação internacional para o “desenvolvimento” ocorre sob condições assimétricas, em que um grupo dominante de atores tem mais poder para definir as regras do jogo (HERMET, 2002; 2003; 2005; HERMET; KAZANCIGIL, 2005; NAVARRO-FLORES, 2007), o que potencializa a ocorrência de conflitos. Também o “desenvolvimento”, termo profundamente ideologizado, constitui outra fonte de conflito incidente sobre o processo de articulação dos atores em torno de ações de cooperação internacional. Esta tese tem por objetivo contribuir para a compreensão do modelo de governança dominante na cooperação Norte-Sul orientada para o “desenvolvimento”. Um estudo de caso interpretativo simples caracteriza o tipo de estudo desta tese, sendo o método de investigação composto por técnicas da Análise Interpretativa bem como pelos métodos de comparação e observação. Como resultados, os dados da pesquisa apontam, entre outros elementos, uma distribuição de recursos centralizada, com foco principal no resultado e na disseminação de “boas práticas”, uma carência de articulação entre os diversos atores implicados, sobretudo com relação à comunicação, além do foco de atenção ser a dimensão instrumental do processo por parte dos atores estratégicos, sem atentar para a dinâmica e para a especificidade do próprio processo.