Visible-light photovoltaic effect in high-temperature ferroelectric BaFe4O7

Abstract

Ferroelectric photovoltaics, as a new type of solar cell, relying 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 elements 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 microscopy (TEM) analyses. UV-vis-NIR diffuse reflectance spectrum revealed a visible-light bandgap E_g of 2.18 eV. Intrinsic ferroelectricity with a high Curie temperature (T_c ∼ 791 K) was confirmed by dielectric and ferroelectric measurements. The electrical saturation polarization (P_s), remanent polarization (P_r) and coercive field (E_c) were determined as 6.34 μC cm⁻², 3.32 μC cm⁻² and 42.38 kV cm⁻¹ respectively. A bulk photovoltaic effect was observed in the poled sample with a steady-state photocurrent of 39 nA cm⁻² and photovoltage of 0.19 V under standard AM 1.5G illumination, which demonstrated its promising applications in photoelectric devices.