Description du poste

The production of hydrogen and solar fuels using photoelectrochemical cells (PEC) is one of the most promising approaches for storing solar energy in the form of clean, carbon-free chemical molecules. These devices are based on photoelectrochemical cells capable of splitting water into hydrogen and oxygen under solar illumination through oxidation and reduction reactions occurring on a semiconductor photoanode and a metal cathode. This approach is known as “artificial photosynthesis.” One of the major challenges of this technology is the high value of the redox potential difference for water dissociation (1.23 eV), which limits the choice of photoactive materials with a wide bandgap, which are often inefficient at absorbing the solar spectrum. To overcome this constraint, one strategy is to spectrally separate (on the same capture surface) the solar flux, with the UV-Visible portion feeding a PEC and the infrared portion feeding a photovoltaic (PV) cell, which provides the additional overvoltage required for photochemical reactions. However, this elegant solution first requires a detailed understanding of the physical phenomena at work in each of the subsystems (PEC and PV), and then in a hybrid system coupling the two. These phenomena are radiation transfer, the photogeneration of electron-hole pairs, their migration by drift-diffusion-reaction, their transfer at interfaces and, in the case of PEC, their participation in artificial photosynthesis reactions. Internship objectives Despite its potential, this hybrid approach remains understudied and raises several fundamental questions: • What efficiency gains can be expected from PEC/PV hybridization? • Which material combinations achieve the best performance? • How do real-world non-idealities (recombination, resistive losses, heating) influence achievable yields? In order to answer these questions, the internship will aim to develop a physical model based on the detailed balance formalism, which is widely used for modeling conventional photovoltaic cells. This formalism will make it possible to calculate the maximum performance of solar-to-hydrogen conversion, based on a model of radiative and energy exchanges incorporating a limited number of physical parameters. The main stages of the work will be: 1. Ideal modeling: 1-a- In the first phase, we will seek to gain an in-depth understanding of the concept of detailed balance applied to PV cells, based on the literature. The principle of detailed balance makes it possible to link the overall behavior of a thermodynamic system to the reversibilities of the properties describing the interactions within it, at the molecular scale (in this case, the light/matter interactions leading to the generation of charges), and the interaction of these charges in electrostatic and electrochemical potential fields. 1-b - The in-depth understanding that will result from this first step should then enable the transposition of the method, applied for the first time to a photoelectrochemical cell (the area of expertise of the supervisors at the Pascal Institute). This work will enable an evaluation of the theoretical maximum performance of the hybrid system as a function of the bandgaps of the PEC and PV cells and the illumination conditions. 2. Taking non-idealities into account: here, we will seek to bring the model closer to the actual behavior of PEC and PV cells observed experimentally by integrating real losses (resistive, non-radiative, thermal) in order to estimate the yields achievable under realistic conditions (based on a demonstrator currently being developed at the Pascal Institute). 3. Sensitivity analysis and optimization: if time permits, the resulting model will be used to identify the critical parameters and most promising configurations for maximizing the overall efficiency of the hybrid system.

Description de l'employeur

The internship takes place at the PROMES-CNRS laboratory in Odeillo (Font-Romeu), in the French Pyrenees, at high altitude (1,600 m), combining a unique mountain setting with world-class solar research infrastructure. PROMES houses one of the largest solar facilities in the world, including a 1 MW solar furnace and a 6 kW solar concentrator for laboratory-scale experiments. This internship is part of a close collaboration with academic partners from the Institut Pascal in Clermont-Ferrand and LAAS-CNRS in Toulouse. It will involve regular scientific exchanges, follow-up meetings, and active participation in inter-laboratory discussions, offering the intern a hands-on immersion in a collaborative research network.

Descriptif du profil recherché

Master's degree student (thermodynamics, statistical physics) or engineering school student with: • a solid background in physics, energy, or thermodynamics, with an interest in modeling, • a keen interest in renewable energies and photovoltaic conversion, • good digital coding skills (Matlab/Python). This internship is for a candidate who is motivated by research and wishes to contribute to the development of new high-efficiency solar conversion technologies at the interface between photochemistry, photonics, and thermodynamics.

Conditions particulières d'exercice

No specific constraint

Langues

French/English