Effect of Ge nanolayer stacking order on performance of CZTSSe thin film solar cells

Abstract In the present work, the effect of germanium (Ge) stacking order on optoelectronic properties of Cu2ZnSn(S, Se)4 (CZTSSe) thin films are investigated. It was found that the addition of the Ge nanolayer significantly improved the CZTSSe absorber quality, elemental distribution, and reduced secondary phases. The Ge nanolayer deposited on top and bottom of the precursor improved open-circuit voltage (Voc) and short-circuit current density (Jsc) in the device respectively. The device with optimum position and thickness of the Ge nanolayer improved device efficiency from 6.91% to 7.87%. Further, these experimental results suggest that the optimum amount of Ge nanolayer and their position can further improve optoelectronic properties of kesterite CZTSSe absorbers which can be used to achieve high-efficiency in kesterite based solar cells.