Giant Bulk Photovoltaic Effect in Penta-PdTe₂ Induced by Layer Stacking

Stacking engineering has emerged as an effective strategy for tuning the physical properties of layered materials. Inspired by the recent experimental synthesis of penta-PdTe₂ sheets [Liu, L.; Nat. Mater. 2024, 23, 1339], we demonstrate, based on systematic symmetry analysis and first-principles calculations, that bilayer penta-PdTe₂ exhibits a strong in-plane polarization; in particular, its ground state possesses a prominent spontaneous polarization (P_s^y = 1.70 × 10^-10 C m^-1), leading to a giant shift current with a value as high as 125.49 μA V^-2, which is much larger than the corresponding values of bilayer penta-PdSe₂ (43.86 μA V^-2) and penta-PdS₂ (29.17 μA V^-2). The underlying mechanism is further elucidated through an analysis of the transition intensity and shift vector distributions in reciprocal space as well as the charge transfer of the X (X = Te, Se, or S) dimers in real space. Our findings highlight pentagonal materials as a promising platform for designing polar materials with strong bulk photovoltaic effect responses.