Performance-limitations in Cu(In,Ga)Se2-based heterojunction solar cells

Cu(In,Ga)(S,Se)₂ (CIGS) solar cells have been modeled using analytical and computer models. A detailed set of parameters was developed for the AMPS computer program along with a procedure for estimating band edge positions from composition depth profiles. Three solar cells were modeled. An ungraded University of Delaware absorber provided a basic set of parameter values. These were modified only in density of defects to model the other devices. Results suggest that the defect density in the absorber limited device performance. Carrier mobilities have a moderate effect on model results, while acceptor density has a much larger effect. In the Shell (Siemens) Solar device, sulfur penetration beyond the depletion region may also have contributed to lower red-response.