Characterization of Cu2ZnSn(S,Se)4 film by selenizing Cu2ZnSnS4 precursor film from co-sputtering process

Cu2ZnSn(S,Se)4 (CZTSSe) films are prepared by selenizing Cu2ZnSnS4 (CZTS) precursor film from co-sputtering of Cu2S, SnS and ZnS targets. The results reveal that the quality of CZTSSe films could be effectively promoted by the selenization temperature. The obtained CZTSSe films have formed a kesterite structure at the selenization temperatures of 500-560 °C and their compositions are all Cu-poor. With the increasing of the selenization temperature, more Se element is incorporated into the CZTSSe films. Especially after being selenized at 540 °C for 30 min, the CZTSSe film possesses a Cu-poor and Zn-rich composition, and an improved crystal quality with suitable atomic ratio (Cu/(Zn+Sn)=0.67, Zn/Sn=1.20, and metal/(S+Se)=1.03). Moreover, it shows strong optical absorption, and its optical band gap (Eg) is found to be 1.41 eV.