LAUSR

Abstract In this work, a model of back-wall superstrate CuIn x Ga 1-x Se 2 (CIGS) thin film solar cell with Glass/SnO 2 :F/CIGS/CdS/ZnO/Ag was established by a simulation tool SCAPS. The influence of bandgap grading, accepter density and the thickness of CIGS layer on the performance of superstrate device has been systematically investigated. The simulation was carried by lighting through SnO 2 :F transparent contact. The simulation results showed that a efficiency of 15.8% could be reached when the graded-bandgap structure near the SnO 2 :F contact was established. However, only slight improvement on the efficiency could be achieved by the graded-bandgap in space charge region (SCR).The result indicates that the key reason which limits the efficiency of the back-wall device is the recombination from the SnO 2 :F/CIGS contact. In addition, in order to achieve high efficiency on the superstrate device, the accepter density in the CIGS layer should be kept below 1.0 × 10 16  cm −3 , and the thickness should be set at 600 nm.