Calcium-doping effects on photovoltaic response and structure in multiferroic BiFeO3 ceramics

Photovoltaic (PV) effects, power-conversion efficiencies, and structures have been systematically measured in (Bi1-xCax)FeO3-delta ceramics for x = 0.05, 0.10, and 0.15. The heterostructures of indium tin oxide (ITO) film/(Bi1-xCax) FeO3-delta ceramics/Au film exhibit significant PV effects under illumination of lambda = 405 nm. The maximum power-conversion efficiency in the ITO/(Bi0.90Ca0.10)FeO2.95 (BFO10C)/Au can reach 0.0072%, which is larger than 0.0025% observed in the graphene/polycrystalline BFO/Pt films [Zang et al., Appl. Phys. Lett. 99, 132904 (2011)]. A theoretical model based on optically excited current in the depletion region between ITO film and Ca-doped BFO ceramics is used to describe the I-V characteristic, open-circuit voltage, and short-circuit current density as a function of illumination intensity. This work suggests that the Ca-substitution can reduce the rhombohedral distortion and stabilize the single-phase structure. (C) 2013 AIP Publishing LLC.