Photo-pyroelectric effect induced by interfacial symmetry breaking in van der Waals contacts for self-powered dual-mode photodetection

The pyroelectric effect from spontaneous polarization offers significant potential for self-powered optoelectronics. However, achieving the macroscopically measurable pyroelectric response remains challenging. Herein, we introduce the pronounced photo-pyroelectric effect in a macroscopically pyroelectric-inactive 2D perovskite, (BA)2MAPb2I7, by constructing the Schottky junction with a high-work-function 2D semimetal layer (i.e., PdSe2), which induces interfacial polar symmetry. The fabricated (BA)2MAPb2I7/PdSe2 van der Waals heterojunction exhibits low dark current, self-powered operation, and two distinct photoresponse modes: a photovoltaic response under 405 nm and a photo-pyroelectric response under 660/860 nm, yielding a pyroelectric coefficient of 7.7 mC m−2 K−1 near 300 K. This value exceeds that of most conventional materials. Furthermore, the device enables dual-wavelength demultiplexing within a single unit, allowing simultaneous reception and decoding of two optical signals. This work demonstrates that interfacial symmetry breaking can facilitate localized dipoles by the built-in field and impart pronounced pyroelectric functionality, providing a strategy for designing multifunctional photodetectors.