Growth of Inorganic Halide Perovskite 2D/3D Heterostructures via Pulsed Laser Deposition (PLD) for Optoelectronics and Photovoltaics

Halide perovskites (HPs) have demonstrated exceptional potential in photovoltaics (PV), achieving record efficiencies (35% in silicon-based tandem cells). However, their limited stability (degradation under humidity, heat, or light) and scalability challenges (efficiency loss at large scale) hinder industrial adoption. Concurrently, in microLED applications, HPs are emerging as a promising alternative to quantum dots (QDs) for color conversion layers, thanks to their high spectral purity and superior absorption. Yet, their efficiency and stability still require optimization to compete with existing solutions.

This project proposes an innovative approach: fabricating inorganic 2D perovskites and 2D/3D heterostructures via pulsed laser deposition (PLD), a scalable and unexplored method for perovskites. 2D perovskites, due to their quantum confinement, exhibit high exciton binding energy, making them ideal for LEDs and lasers, while 2D/3D heterostructures enhance stability and reduce non-radiative recombination.

The thesis objectives are:
1. Synthesis of inorganic 2D perovskites (lead-free and lead-based) via PLD and advanced material characterization (crystallinity, luminescence, absorption, bandgap, stability).
2. Fabrication of 2D/3D heterostructures to achieve defect passivation in 3D layers, with advanced characterization (photoluminescence yield, carrier lifetime, interface passivation).
3. Application in PV and microLEDs: evaluating potential for tandem solar cells and color conversion layers.
The results aim to demonstrate that PLD can overcome current limitations (stability, large-scale production) while maintaining competitive optoelectronic performance. This work aligns with global efforts where perovskites could drive significant advancements in PV and microdisplays

Study of the Metastability of Silicon Heterojunction Solar Cells and Stabilization Strategies

Silicon-based photovoltaic cells, particularly silicon heterojunction (SHJ) cells using hydrogenated amorphous silicon (a-Si:H), achieve efficiencies exceeding 25%. However, these architectures exhibit intrinsic metastability, such as Staebler-Wronski degradation, which can lead to efficiency losses during storage between fabrication and module assembly. In the context of globalized supply chains, these instabilities represent an economic and technical risk that is not yet well quantified. This thesis aims to address the following questions: what is the quantitative impact of instability on the efficiency of high-efficiency cells during prolonged storage? What are the physical mechanisms responsible for this degradation? What technological strategies can reduce or eliminate this instability? What are the industrial implications for module logistics? To achieve this, a rigorous experimental protocol will be implemented to monitor the electrical performance of cells over several months under varying storage conditions (atmosphere, temperature, humidity). Test structures and advanced characterizations (FTIR, Raman, Silvaco TCAD) will be used to understand the underlying physical phenomena. Process optimization, introduction of new materials, and improved packaging will be explored to stabilize the cells. Practical recommendations for the industry, regarding maximum storage durations and optimal storage conditions, will also be established. The goal is to develop technological and logistical solutions to minimize efficiency losses in SHJ cells, optimize supply chains, and reduce associated economic risks.