based on a sole 2D material to have the above two capabilities at the same time. Thus, a crucial issue for the next-generation 2D-material-based photodetectors is to explore a suitable strategy to achieve both high sensitivity and broad-spectrum response.Van der Waals (vdW) heterostructure created by stacking different 2D materials with highly distinct electronic states have shown interesting electronic and optical properties. [7,8] Nowadays, employing vdW heterostructure based on photogating effect demonstrates significant promise for revealing many intriguing physical phenomena and designing optoelectronic devices with superior performance. [8][9][10][11][12][13][14] Rhenium disulfide (ReS 2 ), as a member of the TMDs, has been widely researched due to its high light absorption capability, structural flexibility, and direct bandgap independent of thickness. [15] The photodetectors prepared by a few layers of ReS 2 have shown an ultrahigh responsivity of 88 600 A W −1 , indicating that ReS 2 could serve as a prospective material for future optoelectronic applications. [16] Indium selenide (InSe) has recently been found to display a wide bandgap window ranging from ≈1.25 eV in bulk to ≈2.2 eV in the monolayer. [17][18][19] High carrier mobility (≈10 3 cm 2 V −1 s −1 ) allows for extremely fast response of photodetectors based on InSe and its heterojunctions. [18,20] Thus, it is possible to enhance the overall performance of the photodetector by combining the advantages of InSe and ReS 2 .In this work, a high-performance photodetector based on InSe/ReS 2 vertical heterojunction is fabricated, in which ReS 2 acts as the transport layer, and the top layer InSe serves as the photogate to regulate the channel current. Benefiting from the vertical structure and excellent interface quality, the photodetector demonstrates excellent photodetection ability. On the one hand, the detectivity of the photodetector shows an ultrahigh value of over 10 13 Jones and even over 10 14 Jones at higher drain voltage, which is much higher than other reported photodetectors based on 2D materials. [10,[20][21][22][23][24][25] The photodetector exhibits a high responsivity of 1921 A W −1 , an ultrahigh external quantum efficiency (EQE) of 6.53 × 10 5 %, and a fast response time of 21.6 ms. On the other hand, the photoresponse of photodetectors ranges from the ultraviolet (365 nm) to the near-infrared (965 nm). The ultrahigh sensitivity, broad-spectrum response, and high-efficiency of the photodetector suggest that the InSe/ ReS 2 vertical heterostructure is promising for fast and ultrasensitive broad-spectrum photodetectors. Photogating effect based on vertical structure of 2D materials allows for the realization of a highly sensitive photodetector. A highly sensitive and broadspectrum (365-965 nm) photodetector is reported based on the indium selenide (InSe)/rhenium disulfide (ReS 2 ) vertical heterostructure, where the top layer InSe serves as the photogate to regulate the channel current, enabling a large photoconductive gain of 10 6 . ...

Ambipolar photoresponsivity mainly originates from intrinsic or interfacial defects. However, these defects are difficult to control and will prolong the response speed of the photodetector. Here, we demonstrate tunable ambipolar photoresponsivity in a photodetector built from vertical p-WSe2/n-InSe heterostructures with photogating effect, exhibiting ultrahigh photoresponsivity from −1.76 × 104 to 5.48 × 104 A/W. Moreover, the photodetector possesses broadband photodetection (365–965 nm), an ultrahigh specific detectivity (D*) of 5.8 × 1013 Jones, an external quantum efficiency of 1.86 × 107%, and a rapid response time of 20.8 ms. The WSe2/InSe vertical architecture has promising potential in developing high-performance nano-optoelectronics.