Bifacial Kesterite Solar Cells on FTO Substrates
The thin film kesterite type Cu2ZnSnSe4 (CZTSe) and Cu2ZnSn(SxSe1 x)4 (CZTSSe) chalcogenides are promising materials due to their composition based on earth abundant elements and proven photovoltaic performance in solar cells. The use of transparent back electrodes for photovoltaic applications, adds to this family of thin film devices a plethora of possible technological applications including generating electrical power also from the rear side, thus becoming bifacial devices. This work reports a strategy to improve the transparent back electrode/absorber interface that consists of the insertion of a molybdenum (Mo) or a Mo doped with sodium (Mo:Na) nanolayer between the transparent electrode and the kesterite absorber. The CZTSe and CZTSSe absorbers have been fabricated onto fluorine doped tin oxide (FTO) substrates from sputtered metals followed by reactive annealing on Se+Sn and Se+S+Sn atmosphere respectively, at 525 and 550 degC annealing temperatures. By Raman scattering of the back interface through.