Strain‐Induced Intrinsic Bulk Photovoltaic Effect in Two‐Dimensional GeSe 2

ABSTRACT Given its potential to enhance solar energy conversion efficiency, the bulk photovoltaic effect (BPVE) has attracted considerable attention. Transition metal dichalcogenides (TMDs) have been thriving in the field of BPVE in recent years due to their inversion‐symmetry breaking. However, as a typical narrow‐bandgap semiconductor, TMDs are mainly excited by visible to near‐infrared wavelengths, while the BPVE in the short‐wavelength region has not been investigated. Here, we prepared monoclinic GeSe 2 layered crystals via chemical vapor transport deposition, and systematically studied their in‐plane anisotropic properties. Notably, a significant spontaneous photocurrent was observed in exfoliated GeSe 2 flakes under short‐wave excitation. Comparative studies confirm that the observed BPVE is attributed to ∼0.1% in‐plane tensile strain in GeSe 2 nanosheets. To clarify the intrinsic nature of BPVE in GeSe 2 , we calculated the nonlinear conductivity approximately based on the direction dependence of the photocurrent response to linearly polarized light. The results show excellent agreement with those from the shift current model, demonstrating that an appropriate level of strain can induce the intrinsic BPVE in GeSe 2 . This study fills a gap in the investigation of the short‐wavelength BPVE in layered materials, and reveals the potential of strain engineering to enhance photovoltaic performance.