Photovoltaic Effects in Polarized Polycrystalline BiFeO3 Films

BiFeO3 polycrystalline film has been fabricated using the sol-gel method. X-ray diffraction results indicate that the film adopts random orientation. Ultraviolet-visible (UV-Vis) absorption spectroscopy results show that the film exhibits intense absorbance around 450 nm and a bandgap of 2.66 eV. A significant photovoltaic effect was observed in the BiFeO3 film. The short-circuit current density and open-circuit voltage of the unpolarized film were 6.39 x 10(-5) A/m(2) and 0.21 V, respectively. After polarizing with +15 V and -20 V, the short-circuit current density increased to 9.55 x 10(-5) A/m(2) and 88.98 x 10(-5) A/m(2), respectively. The direction of the short-circuit current could be switched by polarization. The mechanism of the photovoltaic effect was interpreted based on ferroelectric polarization combined with a Schottky barrier model.