We have tested the photovoltaic metrics of CH3NH3PbI3 perovskite solar cells over a wide temperature range from 80-360 K. Our investigation reveals that the open-circuit voltage reaches a maximum value at about 200 K close to the phase transition from tetragonal to the orthorhombic phase. The photocurrent is remarkably stable down to 240 K but drops precipitously upon approaching and below the phase transition temperature, implying inefficient charge carrier generation from the orthorhombic perovskite structure. The impedance spectroscopy measurement suggests ionic motion within the bulk of CH3NH3PbI3 after a phase transition. We propose a plausible mechanism for these phenomena and discuss implications for photovoltage generation and charge carrier transport in CH3NH3PbI3 perovskite solar cells.