Intitulé de l'offre : PhD in Material Science (M/F): Synthesis of flexible solar cells based on CuGaSe2 thin films for indoor photovoltaic applications (H/F)
Référence : UMR6502-THOLEP-002
Nombre de Postes : 1
Lieu de travail : NANTES
Date de publication : lundi 29 janvier 2024
Type de contrat : CDD Doctorant/Contrat doctoral
Durée du contrat : 36 mois
Date de début de la thèse : 1 mai 2024
Quotité de travail : Temps complet
Rémunération : 2 135,00 € gross monthly
Section(s) CN : Condensed matter: electronic properties and structures
Description du sujet de thèse
12.2 billion Internet of things (IoT) devices were already connected in 2021 and forecasts suggest 20 billion in 2025. Among these connected devices, most of them are wireless, operate indoors and are powered through a primary battery which generally lasts between 8 and 25 months. The proliferation rate of IoT devices is so high that in few years hundreds of millions of IoT batteries may have to be replaced every day, implying overhead maintenance costs, not to mention production and recycling or disposal of the batteries. Recent developments in low-power electronics and low-energy wireless communication protocols have considerably lowered the energy and power demand for IoT devices and opened new perspectives for powering them through indoor ambient light energy harvesting.
Indoor photovoltaic devices based on organic or hybrid absorbers have reached significant power conversion efficiency (PCE) and numerous materials have been tested over the past few years. However, they still suffer from stability issues that limit their commercial acceptability. The major conclusion of a recent review on the subject is that “an inorganic solar cell that retains more than 80% of its initial PCE value even after 10 years of its fabrication needs to be developed to compete with the currently used power sources in IoT devices.”
The objective of the project is to produce energy for IoT devices from ambient artificial light using thin film solar cells based on stable, inorganic CuGaSe2 (CGS) chalcopyrite semiconductor grown on flexible substrates. Such devices have the potential to convert up to 50% of the indoor artificial light spectrum since the 1.7eV bandgap of the absorber allows the absorption of all of the above 1.8 eV-photons of the LED spectra without excessive thermalization losses. The synthesis of large-scale, homogeneous, single-phase, wide bandgap CGS thin films is challenging, especially at low temperature, which is necessary for deposition on flexible substrates. Such semiconductor growth being limited by slow kinetics of formation, high efficiency devices are generally obtained using long relaxion steps at high substrate temperature. We recently demonstrated that metal halide post-deposition treatments can be used to drastically decrease the synthesis temperature of CIGS films as well as produce single phase CGS thin film with large grains. This new and unique approach consisting in using metal halides as transport agent enhancing grains growth has therefore all the ingredients to break the technological locks that, to date, restrain the use of stable and industrially compatible CGS compounds for Indoor PV applications on flexible substrates. This project will also focus on heavy alkali post-deposition treatments in a sulphur atmosphere in order to improve the bulk and junction quality based on such absorber, since IMN has developed and masters this type of treatments on narrow bandgap. Finally, the material consumption will be optimized by reducing the thickness of the layers constituting the cell stack and the toxic CdS buffer layer will be replaced by an alternative buffer layer based on non-toxic and earth-abundant materials.
The proposed work will be highly experimental. Hence, the candidate will fully synthesize thin film photovoltaic devices and characterize them both optically and electrically, in order to correlate performance with the synthesis parameters and the material/optoelectronic properties of the synthesized films. The recruited student will be in charge of synthesizing the thin films of CGS by vacuum co-evaporation technique on glass substrates. He/she will also be in charge of the completion of the entire stack (CGS / buffer layer / transparent oxide conductor / grids) that constitutes the solar cell. The person recruited will be responsible for implementing technical solutions for deposition on flexible polyimide substrates. She will also be in charge of developing an optical measurement bench dedicated specifically to indoor measurements. All routine material analyses (XED, SEM, vibrational spectroscopies) will be carried out within the IMN as well as part of the optoelectronic analyses of the devices (IV, EQE, I(V,T)).
Contexte de travail
The proposed PhD thesis will be carried out at the Institut des Matériaux de Nantes Jean Rouxel, in the heart of the city of Nantes, France. It is part of the SIPHON project which is funded by the French National Agency and has been certified by the competitiveness cluster specialized in energy management S2E2. The Institut des Matériaux de Nantes Jean Rouxel (IMN, UMR6502, http://www.cnrs-imn.fr) is a joint CNRS– University of Nantes research unit, composed of more than 200 staff, including about 120 permanent staff and 80 doctoral and post-doctoral students, bringing together physicists and chemists conducting research activities to develop a fundamental understanding of the science of materials and their properties from the atomic scale upwards. This allows the design, characterization and optimization of new materials for a diverse range of high technology applications, including next generation solar cells, fuel cells, electric car batteries, nanotechnology, smart materials, materials for microelectronics, photonic and optical materials. The person recruited will evolve within the MIOPS team (Innovative Materials for Optics, Photovoltaics and Storage) which is involve in several national or international projects in the field of photovoltaics. All the common IMN facilities will be available for the success of the project, in particular microscopies, optoelectronic and vibrational spectroscopies characterization tools.
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 recruited person must hold a Master (or equivalent) from education ensuring deep knowledge in material science and optoelectronic components (especially in photovoltaic devices). She will have to show strong aptitude for experimental sciences (synthesis and analysis), organizational skills, and to communicate easily in English. Knowledge in the field of thin film photovoltaic devices will be an undeniable asset. Travel outside the region will take place during the thesis.