Light trapping in solar cells allows for enhanced absorption beyond the limits imposed by geometrical optics, thus enabling to reduce the solar cell thickness. It permits to reduce the materials costs, increased lifetime of solar cells in space applications and explore new concepts such as hot carrier or intermediate band solar cells which require high density of photo-generated carriers for their operation.In collaboration with world leading research institutes in PV (IPVF, Fraunhofer ISE, NREL, RCAST at The University of Tokyo), we have investigated fundamental aspects of light trapping in nanoscale solar cells, electromagnetic simulations of complete solar cells devices [Goffard2017], the development of large scale and low cost nanofabrication techniques based on direct soft-nanoimprint of sol-gel derived films [Dalstein2016][Bottein2018] and the fabrication of complete solar cells devices. As a result, we have achieved a record short-circuit current for 3µm-thick silicon solar cells in the framework of the NATHISOL ANR [Gaucher2016].
In collaboration with Fraunhofer ISE, we recently worked on 200nm-thick GaAs solar cells and reached an efficiency close to 20% using a light trapping scheme based on a nanostructured TiO2/Ag back mirror. This work has been published in Nature Energy in 2019.
With a similar solar cell architecture, we designed a 150nm-thick CIGS solar cell with the same short-circuit current than state of art CIGS solar cells, which features a 10-times thicker absorber [Goffard2017]. We are currently developing CIGS solar cells with thicknesses as low as 500 nm in the framework of the H2020 project ARCIGS-M. The development of a highly-reflective back contacts has been a key step in the fabrication of ultrathin CIGS solar cells [Gouillart2019,Gouillart2020].