Comprehensive Study of Light-Soaking Effect in ZnO/Cu(InGa)Se 2 Solar Cells with Zn-Based Buffer Layers

The light-soaking effect in ZnO/ Cu(InGa)Se 2 (CIGS) based solar cells has been studied. A CIGS thin film with Cu(InGa)(SeS) 2 surface layer was obtained by selenization (H 2 Se)/sulfurization (H 2 S). A high resistively ZnO buffer layer deposited by the atomic layer deposition technique was used as a buffer layer. We found that the light-soaking effect mainly correlates with the properties of the CIGS surface, rather than with the properties of the ZnO buffer/window layer. This phenomenon can be eliminated by surface etching or doping CIGS surface with Zinc. Zinc diffusion using diethylzinc gas has been proposed in this work. To date, we have achieved efficiency of 13.9% (V oc : 560 mV, J sc : 35.0 mA/cm 2 , FF: 0.71) without light soaking effect.