| Summary: | By engineering strain gradients in dielectrics, the flexoelectric effect can be created, which yields interesting physical properties via electromechanical coupling. Here, we report flexoelectric-induced photovoltaic effects in centrosymmetric LaFeO3 thin-film heterostructures grown on flexible mica substrates, in which partial relaxation of lattice-mismatch strain against LaAlO3 stretching layers results in giant strain gradients and pronounced electrical polarizations. The flexoelectric polarization modulates band alignment and leads to significant photovoltaic effects with a short-circuit current density of ∼0.4 mA/cm2 and an open circuit voltage of ∼ -0.45 V in Pt/LaFeO3/LaNiO3 devices. In addition, by concavely/convexly bending the mica substrate, mechanical strain gradients give rise to bi-directionally tunable photocurrents, in which continuously change of short-circuit current density with a magnitude of ∼100% and good reproducibility in repetitive bending operations are observed in the Pt/LaFeO3/LaNiO3 devices. The present work demonstrates an approach to design self-powered photoelectric devices with an electromechanical degree of freedom based on the flexoelectric effect in flexible thin-film heterostructures.
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