Enhanced visible to near-infrared photodetectors made from MoS2-based mixed-dimensional structures

Two-dimensional (2D) photodetectors based on semiconducting transitional metal chalcogenides (TMDs) have attracted much attention because of its unique mechanical and opto-electronic properties which can be integrated into nanoscale-sized opto-electronic devices and complex circuits. However, the photodetection range of 2D TMDs materials based detectors are generally limited within the visible range due to its intrinsic relatively large band-gap. In addition, 2D TMDs materials also suffers from weak light absorption inherited from their atomically thin layers, resulting in a photoresponsivity that can be further improved. Herein, by combining 2D MoS2 with zero-dimensional (0D) PbSe quantum dots (QDs) and Au nanocrystals (NCs), a novel 2D-0D photo detector (i.e., MoS2/PbSe@Au) is fabricated. Our MoS2/PbSe@Au photodetector exploits the 2D MoS2 as the conduction channels and PbSe@Au NCs as light sensitizer, which promote the absorption of the entire device and enable appreciable photodetection extending to the near-infrared (NIR). Prominently, the mixed-dimensional photodetector exhibits high responsivity of 1.22 A/W and detectivity of 1.56*10(9) Jones (cm.Hz(1/2).W-1) at NIR (e.g., 1064 nm) compared with the MoS2 photodetector with PbSe QDs only, which are ascribed to the more efficient two-step charge transfer process between PbSe and MoS2 with the presence of Au NCs. We further identify the new carrier multiplication mechanism when comparing the photoresponse of our photodetectors at 405 nm and 635 nm. We found the extremely high EQE of MoS2/PbSe@Au photodetector at the wavelength of 405 nm (268.1%) could be ascribed to the synergism of carrier multiplication (CM) in PbSe QDs and the photo gating effect induced by Au nanoparticles. Our study demonstrates that the novel mixed-dimensional photodetectors based on CVD-grown MoS2 may provide a new route for designing and realizing high-performance optoelectronic devices with harvesting merits of hybrid nanomaterials.