Photo-induced electric responses in heterostructure of indium tin oxide/(Bi 1-x Ca x FeO 3-δ /Au,

Abstract

Photovoltaic effects in heterostructure of indium tin oxide (ITO)/(Bi 1_x Ca x )FeO 3_δ multiferroic ceramics/Au (x = 0.0 and 0.15) have been measured under illuminations of λ = 405 and 445 nm. Open-circuit voltage (Voc), short-circuit current density (Jsc), and power conversion efficiency (η) show strong dependences on light wavelength and intensity. For λ = 405 nm, V oc and J sc can reach 0.62 V and 0.042 A/m 2 for BiFeO 3 (BFO), and 0.48 V and 0.30 A/m 2 for (Bi 0.85 Ca 0.15 )FeO 2.925 (BFO-15%Ca) at I N 9.1×10 2 W/m 2 . The maximum power conversion efficiency for λ = 405 nm can reach η N 0.002% for BFO and η N 0.0035% for BFO-15%Ca, which are comparable with 0.0025% observed in graphene/polycrystalline BFO/Pt films. A model based on forward p-n junction, reverse p-n junction and photo-excited currents in the interface between ITO film and (Bi 1_x Ca x )FeO 3_δ ceramic, was developed to describe Voc and Jsc as a function of incident light intensity. The theoretical fits agree well with experimental results. The depletion-region widths for λ = 405 nm were calculated as a function of light intensity. The calculated depletion-region widths without illumination are do N 210 nm in BFO and do N 340 nm in BFO-15%Ca.