Cationic compositional optimization of CuIn(S1-ySey)2 ultra-thin layers obtained by chemical bath deposition

This paper reports the synthesis of CuIn(S1-ySey)2 (CISSe) (y = 0.84-0.93) ultra-thin films prepared by a sequential process based on the chemical bath deposition of In2S3/Cu2-xS precursor layers, followed by annealing under selenium atmosphere. The layers were synthesized varying the [Cu]/[In] ratio from 0.8 to 1.26 and the impact of this variation on the surface region of the ultra-thin absorbers is analyzed for each composition. Through a first optimization of this parameter, we achieved power conversion efficiencies up to 2.7% with open circuit voltage of 334 mV, short circuit current density of 16.1 mA/cm2 and fill factor of 50.9% using a Glass/Mo/CISSe/CdS/i-ZnO/ZnO:Al solar cell structure, for a 600 nm thick absorber annealed at relatively low temperature (450 °C/30 min). This demonstrates that this new synthesis method has potential as a low-cost alternative for CISSe solar cells production.