Application of impedance spectroscopy to investigate the electrical properties around the pn interface of Cu(In,Ga)Se2 solar cells

Abstract The application of impedance spectroscopy (IS) analytical theory to the characterization of Cu(In,Ga)Se 2 (CIGS)-based solar cells was investigated. The equivalent circuit of the CIGS solar cell consisting of series and parallel resistances and a “capacitance-like element” labeled as constant phase element (CPE) around the CdS/CIGS interface was developed. The CPE reflects the depletion layer thickness and the pn interface uniformity and quality. In particular, the CPE- p value, which is an index of impedance of CPE, affects the quality around the CdS/CIGS interface in terms of defect existence and inhomogeneity of the heterojunction. These results show possible candidate for the practical application of IS as a simple method for characterizing the heterogeneity of a pn interface.