Ferroelectric, Photoelectric, and Photovoltaic Performance of Silver Niobate Ceramics

Abstract Ferroelectrics coupled with solar energy conversion are receiving intensive research interest. However, most ferroelectrics with a large remnant polarization can only harvest ultraviolet light in the solar spectrum. Herein, high‐quality silver niobate (AgNbO 3 ) ceramics prepared by spark plasma sintering is reported with a bandgap of ≈2.75 eV and a long tail absorption until 800 nm, leading to outstanding photoelectric properties featured by the visible‐light response over 550 nm. Instantaneous photoresponse measurement using a 355 nm nanosecond pulse laser shows a fast response speed in nanoseconds. Moreover, the ceramic exhibits an intriguing photovoltaic effect under either electric poling or mechanical polishing. Both approaches have switchable characteristics and produce a stable photovoltage as well as photocurrent, while temperature dependence behavior reveals distinctions between ferroelectric polarization and ferroelastic strains in determining the photovoltaic properties. Piezoelectric force microscopy characterization further confirms distinctions between the underlying mechanisms. The electric poling induced photovoltaic effect stems from the aligned polarization involving the ferroelectric component, whereas the mechanical polishing induced photovoltaic effect is associated with the flexoelectricity induced by strain gradients. These results not only show AgNbO 3 to be a promising material for photoelectric application but also deepen the understanding of the mechanism underlying ferroelectric photovoltaics.