Underlying mechanism of the efficiency loss in CZTSSe solar cells: Disorder and deep defects

Abstract

Although Cu2ZnSn(S x , Se1− x )4 (CZTSSe) is a promising candidate for thin-film photovoltaics, its cell performance is currently limited by the large voltage loss. Although a series of studies on the efficiency loss mechanism of CZTSSe solar cell have been carried out in the past few years, no convincing understanding has been obtained until now. In this review, the current findings regarding the underlying mechanism of the efficiency loss in CZTSSe solar cells are systematically summarized and analyzed. The properties of atomic disorder and deep defects in CZTSSe materials and their effects on device performance are discussed. The synergistic effect is proposed to help understand the defect-related charge loss in the absorber. Furthermore, the experimental methods of defect identification and defect control are presented, in an attempt to identify the killer defects that can be responsible for the ultra-short minority lifetime of CZTSSe material. By comprehensively and dialectically understanding these defect properties of the CZTSSe solar cell, we believe breakthrough in the cell efficiency will come soon with our concentrated effort.