Symmetry-breaking-engineered in-plane bulk photovoltaic effect in van der Waals WS/CrOCl heterostructure.

The bulk photovoltaic effect (BPVE), arising from symmetry breaking, has potential to attain conversion efficiencies which surpass Shockley-Queisser limit. Here, we achieve in-plane BPVE in WS/CrOCl heterostructure, attributed to broken-symmetry interfaces by stacking the WS onto anisotropic CrOCl. The breaking symmetry is evidenced by the asymmetric second harmonic generation and angle dependent Raman spectra. The linear - curves demonstrate formation of the BPVE with an open-circuit voltage of 34 mV. Meanwhile, the photocurrent response across the entire channel under zero bias exhibits obvious polarized angle dependence with photocurrent anisotropy ratio of 3.29. The separation of the photogenerated carriers is caused by electric field, originating from in-plane polarization, as demonstrated by piezoresponse force microscopy. This study enhances the understanding of the BPVE and suggests novel strategies for future self-powered devices.