Bulk Photovoltaic Effect Along the Nonpolar Axis in Organic‐Inorganic Hybrid Perovskites

The origin of the bulk photovoltaic effect (BPVE) was considered as a built‐in electric field formed by the macroscopic polarization of materials. Alternatively, the “shift current mechanism” has been gradually accepted as the more appropriate description of the BPVE. This mechanism implies that the photocurrent generated by the BPVE is a topological current featuring an ultrafast response and dissipation‐less nature, which is very attractive for photodetector applications. Meanwhile, the origin of the BPVE in organic–inorganic hybrid perovskites (OIHPs) has not been discussed and is still widely accepted as the classical mechanism without any experimental evidence. Herein, we observed the BPVE along the nonpolar axis in OIHPs, which is inconsistent with the classical explanation. Furthermore, based on the nonlinear optical tensor correlation, we substantiated that the BPVE in OIHPs is originated in the shift current mechanism.