Photovoltaic effect in a wide-area semiconductor-ferroelectric device

Millimeter-diameter planar devices of glass/ZnO:Al/BiFeO3/La0.67Sr0.33CoO3 (LSCO) heterostructures were fabricated by pulsed laser deposition (PLD) techniques. Diode-like behavior with high short-circuit current (SSC ∼ 4 mA/cm2) and open-circuit voltage (OCV ∼ 0.22 V) was obtained under the illumination of about 1% of maximum solar energy. Impedance spectroscopy revealed that electrode/dielectric interface and grain-boundary conduction are mainly responsible for the photo-current. Electrode/dielectric interface, grain boundary impedance, and low-frequency ac conductivity change by almost three orders of magnitude under weak light. Relaxation time of the photo-carriers changes from 80 ms to 96 μs suggesting that with optimal collecting instruments, one should expect currents several orders higher.