Modelling of an equivalent circuit for Cu2ZnSnS4- and Cu2ZnSnSe4-based thin film solar cells

Abstract

The internal resistance and quality of the interface in Cu₂ZnSn(S, Se)₄ (CZT(S, Se)) solar cells were investigated using electrochemical impedance spectroscopy (EIS). We developed an equivalent circuit of the CZT(S, Se) solar cell involving the contact and material resistances R_bulk, two parallel resistances, and a ‘capacitance-like element’ called a constant phase element (CPE) around the CZT(S, Se)/CdS heterojunction and Mo–Mo(S, Se)₂/CZT(S, Se) back-contact interfaces. Using the EIS method, the states of Mo(S, Se) and the CZT(S, Se) layer could be digitised non-destructively. This result can provide guidelines for improving the performance of CZT(S, Se) solar cells or any semiconductor device.