Planner configuration thin film solar cells (TFSCs) with SnS/CdS heterojunction performed a lower short-circuit current (JSC). In this study, we have demonstrated a path to overcome deficiency in JSC by the incorporation of Se in the SnS absorber. We carried out the incorporation of Se in VTD grown SnS absorber by rapid thermal annealing (RTA). The diffusion of Se is mostly governed by RTA temperature (TRTA), also it is observed that film structure changes from cube-like to plate-like structure with TRTA. The maximum JSC of 23.1 mA cm-2 was observed for 400°C with an open-circuit voltage (VOC) of 0.140 V for the same temperature. The highest performance of 2.21% with JSC of 18.6 mA cm-2, VOC of 0.290 V, and fill factor (FF) of 40.9% is observed for a TRTA of 300°C. In the end, we compare the device performance of Se- incorporated SnS absorber with pristine SnS absorber material, increment in JSC is approximately 80% while a loss in VOC of about 20% has been observed.