Antimony selenide (Sb2Se3) is a new thin film photovoltaic material and has received great research attention these days. ZnO, a nontoxic and wide bandgap material, has been successfully applied as the buffer layer in Sb2Se3 solar cells. Device with high efficiency and exceptional stability has been obtained, and ZnO is thus regarded as the most-promising buffer layer for Sb2Se3 photovoltaics. Herein we reported a simple sol-gel method to deposit ZnO film and construct ZnO/Sb(2)Se(3 )heterojunction solar cells. We applied one-step annealing process to obtain smooth and compact ZnO and ZnO/Zn1-xMgxO thin films. We revealed that 10% Mg content was optimal for the sandwiched Zn1-xMgxO layer and finally obtained 4.45% device performance. Through careful characterization, we found out that the insertion of Zn0.9Mg0.1O upshifted the Fermi-level, leading to higher built-in potential (V-Bt) and consequently larger open circuit voltage (V-oc); it also promoted [2 2 1] orientation in Sb2Se3 films and reduced interfacial defects of PN junction, enhancing short-circuit current density (J(sc)).