This work presents a CH3NH3PbI3/PCBM organic solar cell. Organic PCBM film and CH3NH3PbI3 perovskite film are deposited on the PEDOT:PSS/ITO glass substrate by the spin coating method. The performance of the organic solar cells was observed by changing the thickness of CH3NH3PbI3 perovskite. The thickness of a perovskite film can affect the carrier diffusion length in a device that strongly absorbs light in the red spectral region. The short-circuit current density and the power conversion efficiency were 21.9 mA/cm2 and 11.99 %, respectively, for the sample with 210-nm-thick CH3NH3PbI3 perovskite active layer.