Gluing III-V//Si with transparent conductive layers for tandem solar cells

95% of the total photovoltaic production in 2020 is made from silicon. At lab scale, the record efficiency of single-junction silicon solar cells reached 27.6%, close to the theoretical limit efficiency of 29.4%. An alternative way to better exploit the solar spectrum is to combine several semiconductor materials into tandem solar cells, with a theoretical efficiency of almost 45% for an optimal dual-junction Si-based tandem solar cells. The best performances have been obtained by direct wafer bonding of III-V on Si, but this technology is hardly scalable. In this thesis, we designed and developed a new and potentially low-cost gluing method for two-terminal IIIV on silicon tandem solar cells based on transparent, conductive layers (TCLs). This TCL stack is composed of two sol-gel derived antireflection coatings (ARCs) and a low refractive index layer. The ARCs ensure ohmic contacts with the sub-cells and the transmission of low-energy photons to the silicon cell. The low refractive index layer provides both the electrical interconnection between sub-cells and an enhanced photon recycling in the top cell (efficiency gain up to 0.9% absolute). The TCL stack was optimized using optical simulation tools to achieve current matching with minimal current loss, similar to the direct bonding architecture. The lamination process is performed in air, using a simple hydraulic press at low curing temperature (120 deg. C). A reproducible and robust photolithography process at a low temperature of 80 deg. C was also successfully optimized. We fabricated a first generation AlGaAs/TCLs/Si 1 cm² tandem cell with TOPCon Si solar cell and PEDOT:PSS-based glue, showing promising results. A light trapping strategy using a nanostructured layer inserted at the back of the top cell was also explored by electromagnetic simulations, considering practical constraints. This strategy allows to minimize the use of III-V materials by a factor of 2.6. (author)