Ferroelectric photovoltaic and flexo-photovoltaic effects in (1-x)(Bi0.5Na0.5)TiO3-xBiFeO3systems under visible light

The anomalous photovoltaic (APV) effect has witnessed great progress from classical ferroelectric photovoltaics to flexo-photovoltaics. Both call for an extension of the spectral response range. Here, we present a comprehensive study on the ferroelectric, photoelectric, and photovoltaic properties of pure (Bi0.5Na0.5)TiO3(BNT) and 0.3(Bi0.5Na0.5)TiO3-0.7BiFeO(3)(0.3BNT-0.7BFO) ceramics. The data show that pure BNT with typical ferroelectricity exhibits intriguing photovoltaic effect even when illuminated by 550 nm visible light, while the 0.3BNT-0.7BFO solid solution with enhanced visible light absorption shows no ferroelectric photovoltaic due to the negligible ferroelectricity but striking strain-induced flexo-photovoltaic effect. Transmission electron microscopy analysis reveals distinctions in the domain structures and local strain states in pure BNT and 0.3BNT-0.7BFO ceramics, which may account for their differences in photovoltaic behavior. These findings not only deepen the understanding of photovoltaic mechanisms induced by ferroelectric polarization and flexoelectric effect but also highlight a possible candidate for multifunctional photoelectric applications.