Thèse Films de Pérovskite Ultra-Minces Laminés pour Applications Photovoltaïques Lumipress H/F - Doctorat.Gouv.Fr

Établissement : Université Paris-Saclay GS Physique
École doctorale : Ondes et Matière
Laboratoire de recherche : Laboratoire Lumière, Matière et Interfaces
Direction de la thèse : Emmanuelle DELEPORTE ORCID 0000000207650984
Début de la thèse : 2026-10-01
Date limite de candidature : 2026-04-30T23:59:59

Le projet LUMIPRESS vise à produire des films de pérovskite halogénée sans plomb, hautement cristallins, ultra-minces, lisses et parfaitement compatibles avec la fabrication de dispositifs. Grâce à des techniques de lamination par pressage à chaud, le projet permet un contrôle précis de la cristallinité des films, indispensable à la fabrication de dispositifs photovoltaïques haute performance. Le/la doctorant(e) synthétisera les films, les caractérisera morphologiquement et structuralement, et étudiera les propriétés fondamentales de ces matériaux par spectroscopie optique, notamment l'absorption et l'émission de lumière, la dynamique des porteurs de charge, les effets excitoniques et le couplage électron-phonon. Les films seront ensuite intégrés à des dispositifs photovoltaïques afin d'évaluer leur potentiel. Ce projet combine synthèse de matériaux, photophysique et ingénierie des dispositifs, offrant ainsi une plateforme unique pour explorer et optimiser les propriétés optoélectroniques.

Lead-based halide perovskites have demonstrated high and tunable optoelectronic properties [1,2,3], combining strong light absorption, efficient emission, and long carrier diffusion lengths. Due to their easy processability and crystal softness, halide perovskites can be readily implemented in micrometer-thick photovoltaic cells, enabling high-performance photovoltaic applications [1]. However, toxicity and chemical instability remain major barriers for large-scale industrial deployment [4]. The presence of lead raises environmental and safety concerns, while the materials themselves are often sensitive to moisture, oxygen, and thermal stress, limiting device lifetime and reproducibility. Consequently, industrial applications require alternative materials that preserve the functional advantages of lead perovskites while mitigating these fundamental issues.
Lead-free perovskites have recently emerged as a promising alternative.
By replacing lead with elements such as tin, bismuth, or gold, these materials offer a variety of compositions, tunable bandgaps, and adjustable excitonic energies, enabling design flexibility for photovoltaic devices [4]. Gold-based double perovskites [5,6,7], for example, have shown remarkable stability and interesting optoelectronic properties, including strong absorption in the visible and near-infrared and potential for efficient light emission.
Despite this promise, the photophysics of lead-free perovskites is still poorly understood. In particular, the competition between desirable channels-such as efficient charge diffusion or light emission-and self-trapping processes [5] appears to disrupt both charge conduction and optical emission.
Importantly, self-trapping can also give rise to broad luminescence resonances, often referred to as white light, which can be highly appealing for light-emitting devices. These phenomena, together with strong electron-phonon interactions, create complex light-matter interactions that are not yet fully characterized.
Current strategies to fabricate lead-free perovskite thin films compatible with devices face multiple challenges. Achieving ultra-thin, smooth, and pinhole-free layers with controlled thickness and surface morphology remains difficult, which limits device integration. Furthermore, the interplay between film structure, composition, and optoelectronic properties-particularly for two-dimensional perovskite structures -is largely unexplored. Methods to pattern films, such as lamination, press-assisted crystallization [8,9,10] have not yet been applied systematically to lead-free perovskites, leaving a gap in the ability to control light-matter coupling in ultra-thin photovoltaics devices adapted to materials presenting short carrier diffusion lengths.

1/ Develop lead-free, ultra-thin, smooth, and pinhole-free highly crystalline perovskite films with roughness below 50 nm and thickness controllable between 150 and 500 nm, fully compatible with ultra-thin photovoltaic device fabrication.
2/ Investigate fundamental optoelectronic properties, including quantitative assessment of the absorption coefficient as a function of wavelength to reveal phonon-related or electronic effects (indirect bandgap, phonon-induced Urbach tails, excitonic resonances) and their temperature dependence using a cryostat.
3/ Design and fabricate p- and n-type half photovoltaic cells, with separate perovskite layers and selective charge extraction layers, compatible with lamination for full device assembly.
4/ Integrate high-quality films into photovoltaic devices and assess performance, bridging materials synthesis, photophysics, and device engineering.

The LUMIPRESS project addresses the fabrication and fundamental understanding of ultra-thin, pinhole-free and highly crystalline lead-free perovskite films, integrating them into photovoltaic devices. Various lead-free perovskites will be explored, including original 2D ones (or 2D/3D assembled) benefiting from the strong expertise of LuMIn in 2D perovskites. Indeed, 2D perovskites, incorporating large organic cations (such as phenylethylammonium), are easier to crystallize into smooth, pinhole-free thin films, present more stability, and, due to their intrinsic quantum-well structure, give rise to exotic quantum properties (excitonic properties, exciton-phonon coupling) which will be investigated by the PhD student.
The project methodology integrates materials synthesis, thin-film processing, optical characterization, and device fabrication:
1/ Materials Synthesis and Thin-Film Fabrication: LUMIN will prepare high-quality lead-free perovskite single crystals and laminated ultra-thin films (thickness 50-500 nm, roughness <50 nm).
2/ Characterization: Morphological analysis (optical profilometry, SEM), Structural analysis (XRD, confocal and Raman microscopy), optical spectroscopy (absorption, PL, PLE), time-resolved photoluminescence, and cryogenic studies will quantify intrinsic absorption coefficients, PL quantum yields, carrier dynamics, and excitonic properties.
3/ Device Integration: Films will be incorporated into p- and n-type half-cells, which will be laminated to form complete devices with controlled extraction layers.

Formation en physique du solide (physique quantique, bandes électroniques, semi-conducteurs, etc.)
Formation en science des matériaux et physico-chimie des matériaux
Formation en propriétés optiques des matériaux
Une expérience pratique en laboratoire serait un atout (spectroscopie optique, microscopie électronique ou optique, diffraction des rayons X, etc.)
Expérience préalable en synthèse de pérovskites