Flexophotovoltaic Effect and Above-Band-Gap Photovoltage Induced by Strain Gradients in Halide Perovskites
Zhiguo Wang, Shengwen Shu, Xiaoyong Wei, Renhong Liang, Shanming Ke, Longlong Shu, Gustau Catalán
Abstract
We have measured the flexophotovoltaic effect of single crystals of halide perovskites MAPbBr_{3} and MAPbI_{3}, as well as the benchmark oxide perovskite SrTiO_{3}. For halide perovskites, the flexophotovoltaic effect is found to be orders of magnitude larger than for SrTiO_{3}, and indeed large enough to induce photovoltages bigger than the band gap. Moreover, we find that in MAPbI_{3} 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.