Using Cu-Zn-Sn-O Precursor to Optimize CZTSSe Thin Films Fabricated by Se Doping With CZTS Thin Films

The copper-zinc-tin oxide (CZTO) precursor was synthesized to avoid sudden volume expansion from CZTO precursor to Cu₂ZnSnS₄ (CZTS) thin films and smooth CZTSSe thin-film surfaces without pinholes. The CZTO precursor was prepared by coprecipitation and ball milling to form nanoink of CZTO. Based on the CZTO precursor, the CZTS thin film was fabricated and then selenized to make pinhole-free and flat Cu₂ZnSn(S,Se)₄(CZTSSe) thin films. The results show that the CZTO precursor greatly contributed to elevating the homologous surface characteristics and crystallinity of CZTSSe thin films by controlling selenium temperature, selenium time, and selenium source temperature. Finally, the conversion efficiency of the CZTSSe thin-film solar cell fabricated from the CZTO precursor was 4.11%, with an open-circuit voltage (Voc) of 623 mV, a short circuit current density (Jsc) of 16.02 mA cm^-2, and a fill factor (FF) of 41.2%.