A one-step deposition method was adopted to form the organic inorganic mixed halide perovskite (CH3NH3PbI3-xClx) on compact ZnO in order to study the effect of annealing temperature on perovskite film morphology and photovoltaic performance of solar cells. In contrast to the reported results, the perovskite begins to decompose at a pretty low temperature of 70 degrees C. Through careful temperature modulation, we achieved a fairly high efficiency of 9.28%.