Electric-field modulated photovoltaic effect of ferroelectric double-perovskite Bi₂FeMnO₆ films

Ferroelectric perovskite oxide materials for photovoltaics (PV) have received considerable attention for their switchable PV responses and above-bandgap photovoltages as a type of new-generation PV device. Relatively large bandgap and low photocurrent remain major problems for their PV applications. Herein, we report the PV response of ferroelectric double-perovskite Bi₂FeMnO₆ (BFMO) thin films. It was found that the photocurrent density (J_sc) of a Sn:In₂O₃ (ITO)/BFMO/SrRuO₃ (SRO) thin film device is two orders of magnitude higher than that of BiFeO₃, and its power conversion efficiency is about 430 times larger than that of BiFeO₃ under AM 1.5G illumination. The built-in electric field near the BFMO/SRO interface, which represents the Schottky contact, leads to the separation of photon-generated carriers. More importantly, the electric poling treatment on the BFMO device can manipulate significantly the magnitude of J_sc, which is independent of the polarization direction. This electric-field modulated PV effect in the poled BFMO device originates from the modulation of the Schottky barrier height at the BFMO/SRO interface. The redistribution of oxygen vacancies after electric poling treatment is mainly responsible for the modulation of the Schottky barrier height.