The morphology of perovskite film and their relation to the opto-electronic properties is crucial to obtain a high performance perovskite solar cell. The inverted planar perovskite solar cell with configuration ITO/PEDOT:PSS/CH3NH3PbI3/PCBM/Ag was tested, where a post-synthesis treatment using bromide solution was utilized to improve its morphology. The solvent involved in the post-synthesis treatment dissolves the perovskite grains and the bromide retards the crystallization process resulting in a considerable increment in grain size from 260 nm to 3 mu m with a decrement in root mean square (RMS) roughness from 8.127 nm to 5.196 nm. The improved optoelectronic properties of the perovskite film were confirmed by the photoluminescence and electrochemical impedance spectroscopy measurement. The power conversion efficiency of the inverted planar perovskite solar cell showed an improvement from 8.2% without treatment to 14.2% with the post-synthesis treatment.