Blocking current-voltage behaviour of ZnO/CdS/Cu(In,Ga)Se-2/Mo solar cells, which is either temperature-or light-conditioned, is examined using a comprehensive numerical device simulator. Effects of defect states in the defect-chalcopyrite layer and at the CdS/defect-chalcopyrite interface are investigated, Acceptor-like defect states either in a defect-chalcopyrite layer or at the CdS/defect-chalcopyrite interface cause different trapping under red light or white light. This results in different potential profiles throughout the structure, which determine the changeable I-V behaviour under forward bias. Simulation results show that these acceptor-like defect states can also control the temperature-conditioned blocking I-V behaviour.