Superior Plasmonic Photodetectors Based on Au@MoS₂ Core–Shell Heterostructures

Abstract

Integrating plasmonic materials into semiconductor media provides a promising approach for applications such as photosensing and solar energy conversion. The resulting structures introduce enhanced light-matter interactions, additional charge trap states, and efficient charge-transfer pathways for light-harvesting devices, especially when an intimate interface is built between the plasmonic nanostructure and semiconductor. Herein, we report the development of plasmonic photodetectors using Au@MoS heterostructures-an Au nanoparticle core that is encapsulated by a CVD-grown multilayer MoS shell, which perfectly realizes the intimate and direct interfacing of Au and MoS. We explored their favorable applications in different types of photosensing devices. The first involves the development of a large-area interdigitated field-effect phototransistor, which shows a photoresponsivity ∼10 times higher than that of planar MoS transistors. The other type of device geometry is a Si-supported Au@MoS heterojunction gateless photodiode. We demonstrated its superior photoresponse and recovery ability, with a photoresponsivity as high as 22.3 A/W, which is beyond the most distinguished values of previously reported similar gateless photodetectors. The improvement of photosensing performance can be a combined result of multiple factors, including enhanced light absorption, creation of more trap states, and, possibly, the formation of interfacial charge-transfer transition, benefiting from the intimate connection of Au and MoS.

High‐Performance Ultraviolet‐Visible Light‐Sensitive 2D‐MoS2/1D‐ZnO Heterostructure Photodetectors

“…According to the equations above, the R λ and EQE of p‐MoS 2 /n‐ZnO heterostructure PD are calculated to be 24.36 A/W and 8.28×10 3 %, respectively, under an irradiation of 365 nm (5.7 mW/cm 2 ) at +5 V. On the other hand, under an illumination of 532 nm (0.525 mW/cm 2 ) at +5 V, the R λ and EQE are estimated to be 0.35 A/W and 80.9 %. These performance data are superior or comparable to other PDs reported for 2D‐MoS 2 flakes or 1D‐ZnO nanowires, as shown in Table S1 . The R λ and EQE as a dependence of light intensity under 365 nm and 532 nm light illumination are plotted in Figure e and f, respectively.…”

“…Obviously, the t rise and t decay of the devices under UV and green light irradiations are dramatically reduced as compared with individual n‐ZnO nanowire (t rise =3.4 s and t decay =2.2 s) and p‐MoS 2 flake (t rise =18.7 s and t decay =112.9 s), as shown in Figure S5, due to the fast separation of photogenerated electron and hole pairs by the built‐in electric field between 2D‐MoS 2 flake and 1D‐ZnO nanowire. The response time of p‐MoS 2 /n‐ZnO PD is also more competitive to those reported 2D‐MoS 2 flake PDs and 1D‐ZnO nanowire PDs, further demonstrating the advantage of designed p‐MoS 2 /n‐ZnO PD. In addition, similar fast response speed is also observed in as‐prepared n‐MoS 2 /n‐ZnO heterostructure PD under 365 nm (t rise =1.7 s and t decay =2.7 s,) and 532 nm (t rise =1.3 s and t decay =2.2 s) illumination (see Figure S6), indicating the general feature and merits of our designed 2D‐MoS 2 /1D‐ZnO heterostructures.…”

Photoexcited charge carrier behaviors in solar energy conversion systems from theoretical simulations

“…In cases of MoS 2 /WS 2 vdW heterostructures, the VBM resides in WS 2 and CBM MoS 2 , typically a type‐II band alignment, with the valence and conduction band offsets being 0.39 and 0.35 eV, respectively. MoS 2 /WS 2 vdW heterostructures show direct band gap of 1.097 eV, fairly smaller than the band gap of the constituent monolayers . In previous experiment, it has been already illustrated that hole transfer across the MoS 2 /WS 2 geometry gap occurs within 50 fs.…”

“…In MoS 2 , S adatom and S vacancy are the most energetically favorable point defects . On account of introducing trap states, defects will, in principle, destroy the stability and lead to charge carrier loss . It is therefore conclusive that defects will accelerate the nonradiative electron–hole recombination.…”

“…(a) Plasmonic Ag/MoS 2 heterostructures, SEM of Ag nanodiscs, and the corresponding PL maps . (b) Au/multilayer MoS 2 core–shell structure, electric field distribution for Au@MoS 2 from simulations, and the pathways of photoexcited charge carrier generation …”