A compact TiO2 interlayer between fluorine-doped tin oxide (FTO) and perovskite in planar heterojunction perovsldte solar cells is essential for effective charge extraction and minimized recombination. The electrical property of the interface of the perovsldte layer with the compact TiO2 layer is thus important for achieving high power conversion efficiency in the perovskite solar cells. The motivation for the present study was to improve cell performance by improving the property of the TiO2/perovskite interface. Interestingly, a remarkable enhancement in cell efficiency was achieved by treatment of the compact TiO2 layer with TiCl4 and UV(O-3).