Van der Waals PdSe₂/WS₂ Heterostructures for Robust High-Performance Broadband Photodetection from Visible to Infrared Optical Communication Band

Due to excellent electrical and optoelectronic properties, 2D transition metal dichalcogenides and their van der Waals (vdW) heterostructures have attracted great attention for broadband optoelectronics. Here, an unreported vdW PdSe₂/WS₂ heterostructure is developed for robust high-performance broadband photodetection from visible to infrared optical communication band. These heterostructure devices are simply formed by direct selenization of Pd films pre-deposited on the chemical vapor deposited monolayer WS₂, followed by wet-transfer onto device substrates with pre-patterned electrodes. Importantly, the obtained heterostructure device exhibits an impressive broadband spectral photoresponse with response times less than 100 ms for different wavelength regions (532 to 1550 nm), where this performance is significantly better than that of pristine monolayer WS₂ devices. This performance enhancement is attributed to the type I band alignment of the heterostructure. Under illumination, both intralayer and interlayer excitations are involved to generate carriers in the relevant layer, enabling the broadband photoresponse. Photocarriers would then undergo charge separation in the depletion region with electrons transferred into the charge transport layer of WS₂ through the built-in electric field, followed by the relaxation to valance band via interlayer or intralayer transition. All these findings can indicate the promising potential of vdW PdSe₂/WS₂ heterostructures for next-generation high-performance optoelectronics.