van der Waals (vdW) heterodiodes composed of two-dimensional (2D) layered materials led to a new prospect in photoelectron diodes and photovoltaic devices. Existing studies have shown that Type-I heterostructures have great potential to be used as photodetectors; however, the tunneling phenomena in Type-I heterostructures have not been fully revealed. Herein, a highly efficient nn+ WS2/PtS2 Type-I vdW heterostructure photodiode is constructed. The device shows an ultrahigh reverse rectification ratio of 105 owing to the transmission barrier-induced low reverse current. A unilateral depletion region is formed on WS2, which inhibits the recombination of carriers at the interface and makes the external quantum efficiency (EQE) of the device reach 67%. Due to the tunneling mechanism of the device, which allows the co-existence of a large photocurrent and a low dark current, this device achieves a light on/off ratio of over 105. In addition, this band design allows the device to maintain a high detectivity of 4.53 × 1010 Jones. Our work provides some new ideas for exploring new high-efficiency photodiodes.
Keywords: PtS2; Type-I band alignment; heterostructure; photodeterctor; tunneling effect.