Gate-Tunable PdSe2/WSe2 van der Waals Heterostructures for Ultrahigh Light On–Off Ratio Polarization-Sensitive Photodetection
Polarization-sensitive photodetection is critical for advanced optical communication and imaging systems, yet conventional photodetectors suffer from low on-off ratios and limited polarization discrimination. Here, we report gate-tunable PdSe2/WSe2 van der Waals heterostructures that achieve ultrahigh light on-off ratio and polarization-sensitive photodetection. The heterostructure forms a type-II band alignment, enabling efficient charge separation and self-powered operation. By applying a gate voltage, the photoresponse can be modulated, achieving an on-off ratio exceeding 10^6 under illumination. The device exhibits a high responsivity of 1.2 A/W and a specific detectivity of 10^12 Jones at room temperature. Polarization-sensitive measurements reveal a linear dichroism ratio of 2.1 at 532 nm, attributed to the anisotropic crystal structure of PdSe2. The photodetector operates over a broad spectral range from visible to near-infrared (400-1000 nm) with fast response times (rise/fall < 100 μs). The gate-tunable capability allows dynamic control of the photocurrent, enabling adaptive sensing applications. These results demonstrate that PdSe2/WSe2 heterostructures are promising candidates for high-performance, polarization-sensitive photodetectors, offering a pathway for next-generation optoelectronic devices.