Antimony selenide (Sb2Se3) based thin film solar cells have recently drawn a growing research interest due to their increasing power conversion efficiency, proper bandgap, high absorption coefficient, and earth abundant nature. Herein, the Sb2Se3 thin films were prepared by close spaced sublimation (CSS) for efficient Sb2Se3 solar cells. The origin and the mechanisms of shunt current were analyzed. Non-ohmic space-charge limited current (SCLC) was identified to be an important contribution to the nonlinear shunt current in Sb2Se3 thin film solar cells. To tackle this issue, a high-resistance SnO2 buffer was introduced at the front contact. With the insertion of a SnO2 buffer, the micro-shunt paths were modified and a significant efficiency improvement to 5.18% was obtained.