Clément Maheu

Self‐assembled molecules (SAMs) as a molecular charge selective contact and interface with metal oxides are the new benchmark in p‐i‐n devices. Yet, transparent electrode (i.e., ITO) surface preparation is often performed with established protocols that do not exploit the full potential of self‐assembly. We introduce a simple, solution‐based ITO surface treatment strategy that enables improved contact formation by simultaneously tuning surface chemistry, conductivity and homogeneity. Contrary to the prevailing assumption that maximizing surface hydroxylation is the key for phosphonic‐acid‐based SAMs, we show that synthetic design with moderate hydroxyl and hydroxide content yields more uniform and electronically favourable interfaces for SAM anchoring. Electronically, the resulting contacts enable enhanced charge extraction, while offering improved layer homogeneity and operational stability. The treated interfaces further demonstrate improved resilience under extreme thermal cycling between −80°C and 80°C, relevant for low‐earth‐orbit (LEO) space operation. Importantly, we demonstrated the broad applicability of our approach across various materials, fabrication environments, and device structures, including single junction and tandem solar cells. These findings establish surface preparation as a design parameter on par with molecular engineering for robust perovskite optoelectronic devices.

Production photocatalytique d'hydrogène avec des sulfures de métaux de transitions supportés sur TiO2: La photocatalyse est une voie de synthèse prometteuse de l’hydrogène comme carburant solaire. La production photocatalytique est un moyen, à la fois de stocker l’énergie solaire sous forme d’énergie chimique et de produire des carburants de manière renouvelables en utilisant l’eau ou des alcools biosourcés comme matière première. L’objectif de cette thèse est d’étudier la déshydrogénation photocatalytique d’alcools à l’aide de sulfures de métaux de transitions, supportés sur TiO2 (MSx/TiO2). Ces sulfures de métaux de transitions ont des propriétés d’activation de l’hydrogène, des propriétés électrochimiques et des propriétés optiques intéressantes. Une série de sept MSx/TiO2 (M = Co, Ni, Cu, Mo, Ru, Ag, Hg) ont été étudiés. La réaction de déshydrogénation photocatalytique du propan-2-ol est utilisée comme réaction modèle. Des corrélations sont établies entre les propriétés intrinsèques de ces MSx/TiO2 et leur activité photocatalytique. De plus, la mesure d’énergie d’activation d’apparente apporte une compréhension supplémentaire sur les mécanismes photocatalytiques. Cette dernière montre que la production photocatalytique d’hydrogène est principalement limitée par les phénomènes de séparation et de transfert de charges dans les photocatalyseurs. Ainsi, une méthodologie combinant la spectroscopie de photoélectrons UV et la spectroscopie d’absorption UV-Visbile a été mis en place pour déterminer la structure électronique des poudre photocatalytiques. Ce travail conclue sur le caractère central de la structure électronique en photocatalyse. Dans le cas du photocatalyseur RuS2/TiO2, le transfert électronique est l’étape cinétiquement déterminante pour la déshydrogénation photocatalytique du propan-2-ol

When commercial grade electronic devices contain nanomaterials like graphene, it is crucial that these materials resist industrial processes and harsh environments.

An ideal proton exchange membrane should only allow protons to pass and remain impermeable to fuels, as required in fuel cell applications. In methanol fuel cells, high proton conductivity enables high power density, whereas methanol crossover between the electrodes degrades the catalyst activity and lowers efficiency. In conventional polymer membranes, however, conductivity and selectivity are often antagonistic: long transport pathways are needed to achieve selectivity, but these introduce additional ionic resistance. Graphene, a two-dimensional material consisting of a single atomic layer of carbon, intrinsically addresses both requirements. Its basal plane is impermeable to water and other molecules, while still exhibiting a measurable degree of proton conductivity. Here, we show that chemical functionalization of monolayer graphene with sulfophenyl groups significantly enhances its proton transport properties. The conductance increases from 6.9 ± 1.1 to 30.9 ± 2.3 S·cm^-2, while the energy barrier for proton transport is reduced to 6.9 kJ·mol^-1. These findings propose functionalized graphene as an alternative to polymer membranes for electrochemical energy devices.

Immobilizing catalysts on electrodes remains a crucial step in developing electrosynthetic and photoelectrocatalytic systems. An innovative method for immobilizing 2,2,6,6-tetramethylpiperidine N-oxyl (TEMPO), functionalized by an alkoxysilane group, around multi-walled carbon nanotubes via a sol–gel reaction is described. The system demonstrates impressive electrocatalytic performance of benzyl alcohols in carbonate buffer at pH 9.

The first use of the successive ionic layer adsorption and reaction (SILAR) method to grow CdS quantum dots on TiO₂ nanoparticles, achieving efficient photocatalytic alcohol oxidation and H₂ evolution without catalysts or sacrificial donors.