Description du sujet de thèse

Photovoltaics is playing a major role in the energy transition, and its share of electricity production is expected to continue rising towards the 2050 net-zero greenhouse gas emission targets. Over 90% of solar cells produced today use silicon as an absorber material. However, this technology is approaching its physical solar energy conversion limit of 29.4%, with laboratory performance of 27.3%. To overcome this limit, the next generation of solar cells will consist of tandem devices, combining two materials with different gaps, each effective in a different part of the solar spectrum. In the laboratories involved in this project in particular, several materials are being considered in combination with silicon: perovskites, CIGS and III-V materials.
The development of next-generation devices presents a host of challenges: new manufacturing processes, new materials and combinations of materials, new ageing mechanisms and failure modes, and so on. All these aspects require a better understanding of their operating principles, thanks to new methods of characterisation and data analysis. In this project, we propose to take advantage of the recognised expertise of the Centre de Nanosciences et de Nanotechnologies (C2N), the Institut Lavoisier de Versailles (ILV) and their partners, in terms of device characterisation and state-of-the-art equipment.
The aim of the project is to develop a new multi-scale, multi-technique characterisation approach to accelerate the development of reliable, high-efficiency tandem solar cells. Several candidate materials (including perovskites and CIGS) exhibit spatial inhomogeneities ranging from the nanometre to the centimetre scale. The influence of these variations on final device performance and ageing mechanisms remains open. The methods to be combined include photoluminescence, cathodoluminescence, nano-Auger, local XPS and EBSD. In the first year of the thesis, these methods will first be calibrated with known III-V materials, before being applied to CIGS cells, which exhibit pronounced inhomogeneities. In the second and third years, these methods will be extended both to perovskites, which exhibit severe degradation mechanisms, and to samples that have undergone accelerated ageing procedures.

Contexte de travail

This thesis is part of the PEPR TASE MINOTAURE project, which aims to improve the reliability of solar cells through the development of new characterisation methods. It will be carried out in collaboration between the Sunlit teams at the Centre de Nanosciences et de Nanotechnologies (C2N) and the EPI team at the Institut Lavoisier de Versailles (ILV).

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.

Contraintes et risques

The work carried out during this thesis includes experimental work and the use of lasers. Mandatory safety training will be provided.