Double perovskite Bi2FeMoxNi1-xO6 thin films: Novel ferroelectric photovoltaic materials with narrow bandgap and enhanced photovoltaic performance

Double perovskite ferroelectric Bi2FeMoxNi1-xO6 (BFMNO) thin films were fabricated using the sol-gel method. The thin films have a broad-band absorption in visible light range of 400–650 nm. With the increase of Mo content, the optical bandgap decreases from 2.19 eV to 2.07 eV. More importantly, the as-prepared BFMNO thin films have self-polarization behavior that causes the forming of the depolarization field and build-in field in the thin films. The narrow band gap and strong ferroelectric self-polarization play a crucial part in improving the photovoltaic effect. The thin film of x = 0.7 has the optimum open circuit voltage and short circuit current which are 5.41 V and 71.07 μA/cm2 under light illumination of 110 mW/cm2. In addition, the photovoltaic effect of the thin film also exhibits a good adaptability in high temperature environment. This work highlights the applications of the BFMNO thin films as a novel high-performance ferroelectric photovoltaic material.