ED Sciences Chimiques
Gallium arsenide-based photoelectrodes for the production of green hydrogen by artificial photosynthesis
by Fatima MERHI (Institut des Sciences Moléculaires)
The defense will take place at 14h00 - Amphi 1 Bordeaux INP/ENSMAC 16 Avenue Pey Berland 33607 Pessac, FRANCE
in front of the jury composed of
- Gabriel LOGET - Chargé de recherche - CNRS, Université de Bordeaux - Directeur de these
- Bruno FABRE - Directeur de recherche - CNRS, Université de Rennes - CoDirecteur de these
- Valérie KELLER - Directrice de recherche - CNRS, Université de Strasbourg - Rapporteur
- François OZANAM - Directeur de recherche - CNRS, École Polytechnique - Rapporteur
- Christine CACHET-VIVIER - Professeure - Université de Paris 12 - Examinateur
- Damien VOIRY - Directeur de recherche - CNRS, Université de Montpellier - Examinateur
The growing environmental pressures, compounded by the instability that fossil-fuel dependence imposes on the global energy supply, have made the transition toward renewable resources a necessity rather than a choice. Among the possible routes, photoelectrochemical (PEC) water splitting stands out. It uses solar light and water to produce green hydrogen (H2), a clean and storable fuel. This carbon-free technology has proven its efficiency and is widely explored across a broad range of semiconductor (SC) materials. Within this landscape, III-V SCs, such as GaAs and InP attract particular attention for their outstanding optoelectronic properties. Yet despite their high theoretical efficiencies, III-V photoelectrodes remain limited by two obstacles, instability in aqueous media and high cost. This thesis investigates GaAs-based photoelectrodes along two complementary axes: H2 evolution at photocathodes and oxygen (O2) evolution at photoanodes. In the first, GaAs epilayers grown by molecular beam epitaxy (MBE) on p-type Si substrates were combined with transition-metal-based catalysts, Ni and MoS2, to evolve H2 with a Faradaic efficiency exceeding 90 %. The influence of MoS2 morphology and of Ni film and GaAs epilayer thicknesses on the overall system efficiency were also examined. On the photoanode side, the photocorrosion of GaAs under different alkaline conditions was elucidated by combining electrochemical, spectroscopic, and compositional analyses. Integrating a protective and catalytic Ni film enabled the O2 evolution reaction (OER) to proceed on these photoanodes with improved stability. Taken together, these results not only provide an in-depth understanding of how GaAs behaves in PEC systems across different electrolyte compositions, but also establish the viability of GaAs photoanodes for PEC water splitting. In parallel, the study of GaAs/Si photocathodes clarifies the role of each layer within the photoelectrode, opening clear routes toward further improvement. This work ultimately reports the first demonstration of a III-V/Si photocathode for H2 evolution, and successful OER operation on a protected single-junction GaAs:n photoanode.
ED Droit
Limitation periods in labour law
by Doria VANDAELE (COMPTRASEC - Centre de Droit Comparé de Travail et de la Sécurité Sociale)
The defense will take place at 14h00 - Salle des thèses Bâtiment C1, Campus Montesquieu 16 avenue Léon Duguit 33608 Pessac
in front of the jury composed of
- Sébastien TOURNAUX - Professeur des universités - Université de Bordeaux - Directeur de these
- Julien ICARD - Professeur des universités - Université Paris-Panthéon-Assas - Rapporteur
- Dirk BAUGARD - Professeur des universités - Université Paris 8 - Vincennes - Saint-Denis - Rapporteur
- Gilles AUZERO - Professeur des universités - Université de Bordeaux - Examinateur
The development, since 2008, of increasingly short limitation periods within the French Labour Code raises a key question: does labour law now display a limitation regime of its own? This study seeks to answer this question by first proposing a systematic ordering of the limitation rules relevant to this branch of law. Beyond this work of systematisation, the study offers an opportunity to revisit a debate that is structurally central to labour law: that of its distinctiveness. Extinctive prescription, an institution of civil-law origin, provides a privileged vantage point from which to observe the interplay between general and special law. Yet an analysis of positive law reveals an unfinished process of autonomisation. Although the legislature has equipped labour law with limitation periods that derogate from the general law set out in the Civil Code, the latter retains a central role. The study shows that this move towards autonomy has primarily served an objective of securing employment relationships, without a corresponding development of mechanisms designed to guarantee the effective right of employees to access a judge. The persistent dependence on the Civil Code — which takes into account neither the collective dimension of work nor the imbalance inherent in the employee's subordination — emerges as a limitation that needs to be overcome. Indeed, what is at stake is ensuring that the legitimate objective of legal certainty does not undermine the effectiveness of the fundamental right of access to a labour court. In making this observation, the present study does not merely describe positive law: it proposes avenues for building a regime genuinely adapted to the specific features of employment relationships, whether by expanding the grounds for suspension and interruption, redefining the starting point of limitation periods in light of subordination, or shielding labour-law prescription from contractual modification.
ED Sciences de la Vie et de la Santé
Resting-state functional neuroimaging in humans: relevance of the brain's intrinsic network architecture for cognition
by Achille GILLIG (Institut des Maladies Neurodégénératives)
The defense will take place at 14h30 - Amphithéâtre A Bâtiment A29 Université de Bordeaux Campus Talence 351 Cours de la Libération 33400 Talence
in front of the jury composed of
- Marc JOLIOT - Directeur de recherche - Institut des Maladies Neurodégénératives, UMR 5293, Université de Bordeaux, CNRS, CEA - Directeur de these
- Paolo BARTOLOMEO - Directeur de recherche - Paris Brain Institute, Sorbonne Université, Inserm, CNRS - Rapporteur
- Demian WASSERMANN - Directeur de recherche - Centre Inria de Saclay, Université Paris-Saclay, Inria, CEA - Rapporteur
- Alizée LOPEZ-PERSEM - Chargée de recherche - Sorbonne University, Institut du Cerveau – Paris Brain Institute – ICM, Inserm, CNRS, AP-HP, Hôpital de la Pitié Salpêtrière, Paris, France - Examinateur
- Sandra CHANRAUD - Maîtresse de conférences - INCIA - UMR5287 CNRS, Université de Bordeaux, Bordeaux, France - Examinateur
Over the past three decades, functional neuroimaging has profoundly changed how the relationship between brain organization and cognition is studied. While classical approaches sought to localize cognitive functions in circumscribed regions, accumulating evidence has shifted the field toward a network-based understanding of brain function. Resting-state functional MRI has been central to this shift by showing that, even without an explicit task, the brain remains intrinsically organized into coherent resting-state networks. Because these networks partly resemble systems recruited during perception, action, cognition, and emotion, they have often been interpreted as a possible intrinsic architecture supporting mental processes. However, the exact functional meaning of this intrinsic architecture remains unsettled. In particular, it is still unclear whether resting-state networks should be understood as fundamental cognitive modules involved in the offline maintenance of specific cognitive processes. This thesis addressed this question by investigating the relevance of intrinsic brain organization into resting-state networks for cognition, interindividual differences in behavior, and dementia-related cognitive decline. The first contribution was to provide a more precise framework for interpreting the cognitive relevance of resting-state networks. To this aim, we introduced a 33-network resting-state atlas and characterized each network using meta-analytic decoding and consensus-derived cognitive labeling. This aimed to move beyond informal cognitive labels commonly assigned to resting-state networks, by providing empirically grounded associations between intrinsic networks and task-related cognitive processes. It therefore offered a framework in which the proposed cognitive relevance of resting-state networks can be tested. The second contribution challenged the assumption that resting-state networks correspond to strictly specific cognitive modules. Using resting-state functional connectivity prediction of multiple behavioral measures, we showed that connectivity predictive of behavior did not primarily organize at the level of fine-grained cognitive processes, but around broader latent dimensions including Cognition, Positive Affect, and Negative Affect. Crucially, only connectivity predictive of Cognition was associated with a segregated intrinsic architecture, characterized by stronger within-network connectivity and reduced between-network connectivity. This pattern was particularly expressed in networks previously associated with higher-level cognitive processes. These results suggest that cognition relates to a flexible modular intrinsic architecture expressed across multiple networks. The third contribution extended this framework to dementia-related cognitive decline. In memory-clinic patients, we showed that dementia-related steep cognitive decline was associated with global network dedifferentiation, together with a more selective loss of within-networks connectivity. This strengthens the association between network segregation and efficient cognition, while suggesting that dementia alters cognition through two complementary network-level mechanisms, with a global dedifferentiation of large-scale systems and a more selective disruption of the internal cohesiveness of specific networks. Taken together, these studies support a nuanced view of the cognitive relevance of resting-state networks. The intrinsic architecture of the brain does not appear to map onto cognition as a set of fixed, process-specific modules. Rather, resting-state networks appear to constitute a behaviorally meaningful large-scale architecture whose segregated organization supports cognition and whose dedifferentiation accompanies cognitive decline.
ED Sciences Physiques et de l'Ingénieur
Fabrication, characterization and modeling of organic/silicon tandem photovoltaic cells in 3-terminal configuration
by Joan CAPDEVILA (Laboratoire de l'Intégration du Matériau au Système)
The defense will take place at 10h00 - Amphi J.P Dom 321 avenue de la libération, bâtiment A31, 33522 Talence
in front of the jury composed of
- Marie-Estelle GUEUNIER-FARRET - Professeure - Université de Bordeaux - Directeur de these
- Sylvain CHAMBON - Directeur de recherche - Université de Bordeaux - CoDirecteur de these
- Nathanaëlle SCHNEIDER - Directrice de recherche - Institut Photovoltaïque d'Ile de France (IPVF) - Rapporteur
- Olivier DURAND - Directeur de recherche - INSA Rennes - Rapporteur
- Mariano CAMPOY-QUILES - Professeur - Institut de Ciència de Materials de Barcelona (ICMAB-CSIC) - Examinateur
- Stéphane CROS - Directeur de recherche - INES (CEA-Liten) - Examinateur
- Timothée LEVI - Professeur - Université de Bordeaux - Examinateur
Photovoltaics is now a mature technology, largely dominated by crystalline silicon (c-Si), which accounts for more than 98% of the global market. The performance of this technology is now approaching its theoretical Auger efficiency limit of 29.4%, with the best devices achieving conversion efficiencies of 27.9% (lab cells). Multijunction architectures currently represent the most promising route to surpass this limit by reducing thermalization losses through the combination of materials with complementary bandgaps. Among these, silicon-based tandem solar cells have attracted increasing interest for terrestrial applications. Combining a silicon bottom cell, using a well-established industrial process, with a wide-bandgap top cell (e.g., perovskite or CIGS) extends the efficiency limit of single-junction devices, with record efficiencies now exceeding 33%. At the same time, recent advances in organic photovoltaics (OPV), with laboratory cells reaching efficiencies up to 20%, together with the unique properties of organic semiconductors (including their wide range of available materials, tunable bandgaps, high optical absorption coefficients, and compatibility with low-cost fabrication processes), make this technology an attractive candidate for tandem integration with silicon. Within this context, and as part of the ANR ORGANIST project, this thesis aims to develop the key technological building blocks required to realize a tandem solar cell combining a wide-bandgap semi-transparent OPV top cell with an interdigitated back-contact (IBC) crystalline silicon bottom cell. A three-terminal (3T) architecture was selected because it eliminates the current-matching constraints and the need for tunnel junctions inherent to conventional two-terminal tandem devices. The first part of this work focuses on the development of the wide-bandgap organic top cell based on the PM6:GS-ISO bulk heterojunction. Optimization of the fabrication process, combining thermal treatments, solvent engineering, and conjugated solid additives, improved the crystallinity of the active layer, enhanced its optical properties, and reduced recombination losses, leading to power conversion efficiencies of 10% with an open-circuit voltage (VOC) of 1.20 V. The second part of the thesis addresses the development of a transparent top electrode based on indium tin oxide (ITO), deposited at room-temperature by magnetron sputtering and combined with a MoO3 layer providing both protection of the organic layer and efficient hole transport. Optimization of the deposition parameters enabled the fabrication of semi-transparent organic solar cells with efficiencies close to 6% and VOC values exceeding 1.1 V. These developments enabled the first integration studies of a semi-transparent organic solar cell with an IBC silicon solar cell in a 3T architecture. Interface investigations demonstrated the potential of sputtered ITO as an interconnection layer owing to its high optical transparency, low electrical resistance, and compatibility with both organic and silicon photovoltaic technologies. Finally, a concept named RAINBOW, developed in collaboration with ICMAB-CSIC (Barcelona), was introduced to make the link between experimental results and modeling for the investigation of lateral organic/silicon multijunction architectures. Simulations predict efficiencies of up to 18% (for a silicon cell efficiency of approximately 16%), confirming the potential of these hybrid structures and providing valuable guidance for the development of future generations of high-efficiency organic/silicon tandem solar cells.
ED Sociétés, Politique, Santé Publique
Characterization of complex posttraumatic stress disorder (CPTSD): Study of emotional dysregulation and dissociation
by Jordan TEYSSEYRE (Laboratoire de Psychologie)
The defense will take place at 13h30 - Amphithéâtre E 3 ter Place de la Victoire, Bâtiment E, 33000 Bordeaux.
in front of the jury composed of
- Géraldine TAPIA - Maîtresse de conférences - Université de Bordeaux - Directeur de these
- Fabien D'HONDT - Professeur des universités - Université de Lille - Rapporteur
- Nelly GOUTAUDIER - Professeure des universités - Université de Poitiers - Rapporteur
- Wissam EL-HAGE - Professeur des universités - praticien hospitalier - Université de Tours - CoDirecteur de these
- Katia M'BAILARA - Professeure - Université de Bordeaux - Examinateur
- Marion TROUSSELARD - Professeure agrégée - Ecole des Psychologues Praticiens - Examinateur
The International Classification of Diseases (ICD-11; World Health Organization, 2022) recently included complex posttraumatic stress disorder (CPTSD) as a related form of posttraumatic stress disorder (PTSD). CPTSD is defined by six symptom clusters: three shared with PTSD (re-experiencing, avoidance, and sense of threat) and three distinct clusters related to disturbances in self-organization (affective dysregulation, disturbances in relationships, and negative self-concept). To date, the literature reflects a lack of data regarding the characterization of CPTSD, which nonetheless constitutes a major mental health issue. Among the range of processes associated with trauma-related disorders, emotional dysregulation (Jannini et al., 2025; Raysséguier, Teysseyre, et al., in press) and dissociation (Fung et al., 2023; Hamer et al., 2024) appear to occupy a central role in CPTSD. However, targeted investigation of these processes remains limited and needs to be strengthened through person-centered and quasi-experimental approaches in emotional contexts. The aim of this thesis was to strengthen the characterization of CPTSD through two sub-objectives: (i) to identify and compare the sociodemographic, clinical, and psychopathological characteristics of patients with CPTSD and PTSD; (ii) to examine the specific involvement of emotion (dys)regulation and dissociation processes in PTSD and CPTSD. Study 1 aimed to identify distinct profiles of post-traumatic symptoms based on the ICD-11 conceptualization, and to identify potentially traumatic exposure and mental health correlates associated with PTSD and CPTSD profiles. Results notably revealed four symptom profiles, including a low-symptomatology profile, a PTSD profile, and two CPTSD profiles that differed by their level of emotional hypoactivation. Studies 2 and 3 aimed to identify distinct profiles of emotional dysregulation (Study 2) and dissociation (Study 3), and to examine the distribution of individuals with PTSD or CPTSD across these profiles in order to establish whether certain patterns of functioning were specific to PTSD or CPTSD. Results from these studies revealed six distinct profiles of emotional dysregulation (Study 2) and five distinct profiles of dissociation (Study 3). In both studies, while no profile was specifically associated with PTSD, individuals with CPTSD were systematically over-represented in the two most severe profiles and under-represented in the low-symptomatology profiles. Finally, in light of the limitations inherent to the design of the previous studies, Study 4 aimed to investigate emotional and dissociative processes in an emotional context. This study's objective was to explore subjective and physiological responses during exposure to trauma-related stimuli in individuals with CPTSD compared to control participants. Results revealed a desynchrony between subjective disturbance and the associated cardiac autonomic response in individuals with CPTSD, suggesting a possible rigidity of autonomic regulation, potentially related to dissociation. Taken together, the findings of this thesis support the validity of PTSD and CPTSD as two distinct clinical entities, differing both in severity and in nature. These findings open avenues for understanding trauma-related disorders and offer scientific and clinical perspectives for optimizing the assessment and treatment of these disorders.