LAUSR

Abstract CuGaS 2 thin films were obtained by sulfurization of CuGaSe 2 . CuGaSe 2 thin films were first electrodeposited from aqueous solutions containing CuCl 2 , GaCl 3 , and H 2 SeO 3 and subsequently annealed at 400 °C for 10 min in forming gas atmosphere and in the presence of molecular sulfur. This sulfurization process resulted in the complete conversion of CuGaSe 2 into CuGaS 2 . The formation of CuGaS 2 was proven by X-Ray diffraction and optical spectroscopy. Diffraction peaks of CuGaS 2 shifted to higher angles than those observed for CuGaSe 2 films, and the optical band gap shifted to blue rising from 1.66 eV for CuGaSe 2 to 2.2 eV for CuGaS 2 . When Cr ions were added to the initial electrolyte, the final CuGaS 2 films exhibited a broad in-gap absorption band centred at 1.63 eV that can be attributed to Cr atoms at the Ga sites. The performance of solar cells based on CuGaS 2 :Cr absorbers containing an in-gap absorption band was then estimated by numerical simulation using Solar Cell Capacitance Simulator Software. Both quantum efficiency and short circuit current of simulated Mo/CuGaS 2 :Cr/CdS/ZnO solar cells rose proportionally to the amount of Cr present in the CuGaS 2 :Cr absorbers. As a result, the photo conversion efficiency of the simulated devices changed from 14.7% for CuGaS 2 to 34% for CuGaS 2 :Cr absorbers. Nevertheless, when neutral defects related to Cr-doping were introduced in the absorber layer, the positive effect of the enhancement of photon harvesting due to IGB was compensated by a decline in the carrier collection and the overall efficiency of the device diminished considerably.