Visible-light Photovoltaic effect in High-Temperature Ferroelectric BaFe4O7
Ferroelectric photovoltaics as a new type solar cell, relied on an internal electric field instead of p-n or Schottky junctions, can considerably improve the efficiency of charge separation and migration. But, non-volatile element containing ferroelectrics with narrow bandgaps and excellent photoelectric performances are still scarce. Herein, a new ferroelectric compound, BaFe4O7, has been synthesized by a conventional hydrothermal method. A polar trigonal structure (P31c) was proposed by X-ray diffraction (XRD) and transmission electron microscope (TEM) analyses. UV-vis-NIR diffuse reflectance spectrum revealed a visible-light bandgap Eg of 2.18 eV. The intrinsic ferroelectricity with a high Curie temperature (Tc ~ 791 K) was confirmed by dielectric and ferroelectric measurements. The electrical saturation polarization (Ps), remanent polarization (Pr) and coercive field (Ec) were determined as 6.34 µC/cm2, 3.32 µC/cm2 and 42.38 kV/cm respectively. A bulk photovoltaic effect was observed in poled sample with a steady-state photocurrent of 39 nA/cm2 and photovoltage of 0.19 V under standard AM 1.5G illumination, which demonstrated the promising applications in photoelectric devices.