Flexophotovoltaic Effect and Above-Band-Gap Photovoltage Induced by Strain Gradients in Halide Perovskites

We have measured the flexophotovoltaic effect of single crystals of halide perovskites MAPbBr3 and MAPbI3, as well as the benchmark oxide perovskite SrTiO3. For halide perovskites, the flexophotovoltaic effect is found to be orders of magnitude larger than for SrTiO3, and indeed large enough to induce photovoltages bigger than the band gap. Moreover, we find that in MAPbI3 the flexophotovoltaic effect is additional to a native bulk photovoltaic response that is switchable and ferroelectric-like. The results suggest that strain gradient engineering can be a powerful tool to modify the photovoltaic output even in already well-established photovoltaic materials.Received 13 July 2023Accepted 5 December 2023DOI:https://doi.org/10.1103/PhysRevLett.132.086902© 2024 American Physical SocietyPhysics Subject Headings (PhySH)