Photovoltaic Property of Multiferroic ${\hbox {BiFeO}}_3$ Films With Different Textures on Glass Substrates

The photovoltaic (PV) property of multiferroic BiFeO₃ (BFO) nanocrystalline films with different textures on glass substrates has been studied. Highly textured BFO(001) films were obtained on ferromagnetic L10-FePt(001) bottom electrodes by sputtering, while the isotropic polycrystalline BFO films were prepared on 20-nm-thick Pt(111) bottom electrodes by pulse laser deposition. All studied BFO films exhibited significant PV effect under laser illumination with wavelength of 405 nm, and the short-circuit photocurrent density was increased with the increase of laser intensity. Large photocurrent density ( Jsc) of 5.9 μA/cm² at laser power of 220 mW/cm² was obtained in the BFO(001) film grown on 20-nm-thick FePt electrode, and the value was larger than that of the isotropic single phase BFO film by a factor more than 1.7. This difference could be explained by the depolarization effect along different lattice orientations. Furthermore, it was found that the larger compressive residual strain in the BFO(001) film leads to a 34% decrement in Jsc, which was believed to result from the widened band gap. PV property was also sensitive to phase and roughness, the formation of Bi₂O₃, and a roughened surface suppresses PV effect.