Symmetry-breaking engineered for polarization-sensitive bulk photovoltaic effect in b-As/2H-TMDs heterostructures

The bulk photovoltaic effect (BPVE) provides a junction-free route to spontaneous photocurrent and photovoltage beyond Shockley-Queisser limit. Current BPVE designs mainly rely on interfacial symmetry breaking induced by low-symmetry materials, yet the resulting interfacial polarity and symmetry-breaking strength are often constrained by the constituent symmetry, orbital polarizability and interfacial charge redistribution, restricting further enhancement of BPVE. Here, we realize a symmetry-engineered BPVE by vertically stacking twofold-symmetric black arsenic (b-As) with threefold-symmetric 2H-phase transition metal dichalcogenides (2H-TMDs, including MoS₂, WSe₂ and SnS₂), and establish a correlation among constituent symmetry, interfacial symmetry breaking and BPVE response. The symmetry-mismatched interface generates an in-plane polarization that drives a strong BPVE along the armchair axis. Optimized b-As/WSe₂ devices deliver a responsivity of 946 mA/W, a detectivity of 9.28 × 10⁹ Jones and a BPVE coefficient of 0.95 V^-1 at 638 nm, outperforming most previously reported vdW BPVE devices. Comparative results further reveal that stronger interfacial polarity, originating from the larger orbital polarizability of heavier constituent atoms, promotes enhanced BPVE response. In addition, the devices show pronounced polarization sensitivity, with a dichroic ratio of 10.82 at 638 nm, further corroborating the strong interfacial polarity. These results reveal a materials symmetry response relationship for interfacial BPVE and provide a rational design principle for realizing giant, polarization-sensitive BPVE in van der Waals heterostructures.