High-Performance Gate-Voltage-Tunable Photodiodes Based on Nb ₂ Pd ₃ Se ₈ /WSe ₂ Mixed-Dimensional Heterojunctions

The mixed-dimensional (MD) van der Waals (vdWs) heterojunction for photodetectors has garnered significant attention owing to its exceptional compatibility and superior quality. Low-dimensional material heterojunctions exhibit unique photoelectric properties attributed to their nanoscale thickness and vdWs contact surfaces. In this work, a novel MD vdWs heterojunction composed of one-dimensional (1D) Nb₂Pd₃Se₈ nanowires and two-dimensional (2D) WSe₂ nanosheets is proposed. The heterojunction's energy band engineering is accomplished by manipulating the Fermi level of the bipolar 2D material via gate voltage, resulting in a rectification characteristic that can be adjusted with gate voltage. Under 685 nm laser irradiation, it demonstrates exceptional self-powered photodetection performance, attaining a photoresponsivity of 1.45 A W^-1, an ultrahigh detectivity of 6.8 × 10¹² Jones, and an ultrafast response time of 37/64 μs at zero bias. In addition, a broadband photodetector from 255 to 1064 nm is realized. These results demonstrate the great potential of Nb₂Pd₃Se₈/WSe₂ MD heterostructures for advanced electronic and optoelectronic devices.