Grain boundary recobination activity in Cu(In,Ga)Se2 solar cells with ion-polished flat surface

Grain boundaries should not act as effective recombination centers in high efficiency polycrystalline Cu(In, Ga)Se₂ (CIGS) solar cells. In this study, a CIGS surface was ion-polished to make a flat surface, which eliminates the influence of surface features in electron-beam-induced-current (EBIC) measurement. Solar cells using the CIGS films with and without the ion polishing showed almost similar efficiency. This indicates that the ion polishing did not cause a serious damage on the surface or the damage was eliminated during the solar cell fabrication process. The solar cell without the ion polishing showed lower EBIC signals at grain boundaries, meaning that the EBIC image was influenced by the surface feature. In contrast, the EBIC image for the solar cell with the ion polishing hardly showed the surface feature. The result indicates that there was no distinct difference between the recombination at intra grains and grain boundaries.