Antimony selenide (Sb2Se3) has emerged as a promising absorber material for thin film solar cell (TFSC) application. In this work, a (120) oriented substrate-configured Sb2Se3 based TFSC has been fabricated using the thermally evaporated Sb2Se3 thin films. Pre-synthesized bulk Sb2Se3 was used as a source material and the films were subjected to post-deposition selenization. TFSCs were fabricated in a device configuration of Glass/Mo/Sb2Se3/CdS/ITO/Ag. It was found that there is a significant increment in the power conversion efficiency (PCE) with increased Voc and Jsc in the devices, wherein the Sb2Se3 absorber films were subjected to post-deposition selenization compared to the devices made with as-deposited films. TFSC with as grown Sb2Se3 film was showing an efficiency of ∼ 1% with Voc ∼ 208 mV, Jsc∼16 mA cm−2 and fill factor (FF) ∼ 29.9%. The device with selenized Sb2Se3 films showed a power conversion efficiency of 3.38% with Voc, Jsc and FF values of 362 mV, 18.54 mA cm−2 and 50.39%, respectively. The increase in PCE for selenized films is attributed to better grain growth and suppression of selenium vacancy defects. Overall, the findings of this work demonstrate the potential prospects of Sb2Se3 as an absorber material for TFSCs applications and suggest that post-deposition selenization plays a significant role in the enhancement of device efficiency. The obtained results are contributive in the understanding and development of low-cost Sb2Se3-based TFSCs.