The switchable photovoltaic effect in BiFeO3 thin films capacitors has been studied extensively. However, the origin of the photovoltaic response is still under debate. Both bulk depolarization field and interface effects have been used to explain the observations. In this work, we fabricate BiFeO3 epitaxial films on SrTiO3 substrate with La0.7Sr0.3MnO3 and Pt as electrodes. Much larger switchable photovoltaic response can be observed in the Pt/BiFeO3/La0.7Sr0.3MnO3 samples, as compared with La0.7Sr0.3MnO3/BiFeO3/La0.7Sr0.3MnO3. Moreover, the photovoltaic voltage of the Pt/BiFeO3/La0.7Sr0.3MnO3 samples is nearly independent of the thickness of the La0.7Sr0.3MnO3 bottom electrode. We suggest that the Schottky barrier modulation by ferroelectric polarization at the Pt/BiFeO3 interface is mainly responsible for the photovoltaic effect, with very small contribution from the bulk depolarization field.