Non‐Stoichiometry Induced Switching Behavior of Ferroelectric Photovoltaic Effect in BaTiO 3 Ceramics

Ferroelectric photovoltaic (FPV) effect has been studied among a series of non-stoichiometric BaTiO3 (Ba/Ti = 0.921.05) ceramic chips prepared by tape casting method. The FPV performance increases abruptly when the Ba/Ti molar ratio deviates from the stoichiometry within 1%. Meanwhile, a photocurrent direction switching behavior is observed between Ti-excess and Ba-excess samples. The TEM analysis shows their significant difference in grain-boundary (GB), where abnormal GB with a width of 1015 nm is observed in Ba-excess sample. The photocurrent switching phenomenon is described to the competition between the asymmetrical Schottky barriers induced PV effect and intrinsic FPV effect. Widen GB in Ba-excess BaTiO3 ceramics restrains the intrinsic FPV effect and results in the switching behavior. This study offers direct evidence of the vital role of GB in FPV effect and may promote the development of photovoltaic devices.