Domain-wall photovoltaic effect in ferroelectric perovskite oxides

Abstract

Ferroelectric materials exhibit a unique photovoltaic (PV) response that conventional pn junctions of semiconductors do not show. Above bandgap photovoltages, light-polarization-dependent photocurrents, photocurrent generation by terahertz light, etc. in ferroelectric PV effect are attractive features for novel optoelectronic devices. Recent studies on the ferroelectric PV effects have revealed that ferroelastic domain walls (DWs) are an active center for the generation of photocarriers. In this review paper, firstly, the history and status of studies on the DW-PV effect are briefly surveyed. Then, an analysis method that we have developed to experimentally quantify the magnitude of the PV response in the DW regions is introduced for BiFeO3-based ferroelectric epitaxial thin films. Moreover, materials design strategies for further enhancement of the photoresponse based on the engineering of impurity levels, domain structures, and their combinations are presented.