A combination of a mesoporous brookite layer prepared at 150 degrees C and an ultrathin sputtered compact TiO2 layer was employed as an electron collector of CH3NH3PbI3-xClx perovskite solar cells on an indium tin oxide-polyethylene naphthalate (ITO-PEN) plastic film. The significant contribution of the 8 nm-thick compact layer on ITO to suppressing recombination was clarified; this contribution resulted in a high power conversion efficiency of up to 13.8%.