Effect of top electrodes on photovoltaic properties of polycrystalline BiFeO3 based thin film capacitors.

We investigated capacitors based on polycrystalline narrow-band-gap BiFeO(3) (BFO) thin films with different top electrodes. The photovoltaic response for the capacitor with a Sn-doped In(2)O(3) (ITO) top electrode is about 25 times higher than that with a Au top electrode, which indicates that the electrode plays a key role in determining the photovoltaic response of ferroelectric thin film capacitors, as simulated by Qin et al (2009 Appl. Phys. Lett. 95 22912). The light-to-electricity photovoltaic efficiency for the ITO/polycrystalline BFO/Pt capacitor can reach 0.125%. Furthermore, under incident light of 450 µW cm(-2) and zero bias, the corresponding photocurrent varies from 0.2 to 200 pA, that is, almost a 1000-fold photoconductivity enhancement. Our experiments suggest that polycrystalline BFO films are promising materials for application in photo-sensitive and energy-related devices.