Influence of deposition potential on Cu₂ZnSnS₄thin–film solar cells co–electrodeposited on fluorine–doped tin oxide substrates

Earth–abundant Cu₂ZnSnS₄(CZTS) thin–film photovoltaic absorbers were synthesised by co–electrodeposition of Cu–Zn–Sn–S precursors on fluorine–doped tin oxide (FTO) coated glass substrates, followed by sulfurization in a sulfur atmosphere. In this paper, we investigated the effects of deposition potential on the properties of CZTS thin films and the photovoltaic performance of solar cells made with them. Initial increases in deposition potential increase the Zn content, decrease the Cu content, increase grain size, and improve the crystalline quality of the films. This boosts open circuit voltage (V_oc) and short circuit current density (J_sc), thereby enhancing the efficiency of resulting solar cells from 0.56% to 4.73%. However, further increases in deposition potential cause rough surfaces, which reduces device performance by lowering V_ocand increasing series resistance (R_s). This is the first study of CZTS thin–film solar cells made via co–electrodeposition on FTO–coated glass substrates at various deposition potentials. It provides a novel and promising method for fabricating high–efficiency CZTS bifacial thin–film solar cells.