Abstract Copper and Zinc selenates were synthesized by wetchemical method employing selenic acid. The selenates were mixed with SnS2 in the ratio of 1:1:1 and annealed at 350˚and 450 °C to obtain CZTSSe. The synthesized CZTSSe possess absorption coefficient as high as 105 cm−1. The obtained band gap of the samples are 1.62 and 2.69 eV. Hall measurements on the thin film of CZTSSe indicate high mobility (∼104 cm2 V−1 s−1). As a proof of concept, I-V characterization of SLG/FTO/ZnO/CZTSSe/Ag heterojunction device is studied at 1.5AM illumination. The photovoltaic efficiency of the device based on CZTSSe-350 °C and CZTSSe-450 °C is found to be 1.24% and 0.64% respectively. Thus, the synthetic procedure of sulfo-selenization via selenates and sulfides can act as an option to scale up CZTSSe for photovoltaic applications.