Enhancement of Cu(In,Ga)Se2 solar cells efficiency by controlling the formation of Cu-deficient layer

The effects of deposition time of the second stage (t(2nd)) and the third stage (t(3rd)) during the three-stage process on the formation of Cu-deficient layers (CDLs) at Cu(In,Ga)Se-2 (CIGS) near-surface were investigated in this study. The experimental findings suggested that the CDL was thickened by a longer deposition time in the third stage. Also, the device performance was found to deteriorate with the increased thickness of CDLs, suggesting that the CDL has a defect concentration higher than that of CIGS thin films. Furthermore, the peak position of electron beam induced current signal was shifted towards the interior region of CIGS films, confirming the n-type conductivity of CDLs. The highest conversion efficiency of 19.0% was obtained in this work when the thickness of CDL was 80 nm.