2. Experimental details
2.1. Fabrication of CZTS powders by ball milling
Commercially available binary-alloy powders of copper sulfide (Cu2S), zinc sulfide (ZnS) and tin sulfide (SnS2) were weighted and mixed in atomic ratio of Cu:Zn:Sn:S = 2:1:1:4, corresponding to the stoichiometry of Cu2ZnSnS4. The mixed powders and stainless steel balls were loaded in Altiratinib stainless steel vial, which was filled with argon in a glove box. Ball-to-powder weight ratio was maintained at 5:1. In order to decrease the agglomeration of milled powders, absolute ethanol used as dispersant was filled into the vial up to submerge the powder mixtures and milling balls. The mixed powder was milled in a high-energy ball mill for 10–25 h, and then collected by evaporating ethanol under vacuum at 60 °C.
2.2. Preparation of CZTSSe film
2.3. Fabrication of device
CZTSSe solar cell devices with traditional structure i.e. SLG/Mo/CZTSSe/CdS/i-ZnO/indium-tin-oxide (ITO)/Al grid, were prepared. The CdS buffer layer (∼50 nm) was deposited by chemical bath deposition, as shown in Ref. , and then, i-ZnO (∼70 nm) and ITO (∼250 nm) were sputtered on top of CdS followed by thermal evaporation of Al grid electrode (2 μm) on top of ITO layer. Finally, the whole device was mechanically scribed into 4 small cells with the active area of about 0.39 cm2.