Highly efficient and flexible photodetector based on MoS2–ZnO heterostructures

Plasmonic MXene Nanoparticle-Enabled High-Performance Two-Dimensional MoS2 Photodetectors

Two-dimensional (2D) molybdenum disulfide (MoS₂) has emerged as a prospective candidate for photodetection. However, due to the surface defects formed during the synthesis, the low photoresponse of 2D MoS₂ photodetectors restricts its practical applications. Here, we developed a hybrid plasmonic structure that integrates MXene nanoparticles (MNPs) and 2D MoS₂. With the introduction of MNPs, light waves are concentrated on MoS₂ nanosheets via a strong localized surface plasmon resonance. Consequently, MNPs-decorated MoS₂ photodetectors exhibit an improved photoresponse, including a higher responsivity (20.67 A/W), a larger detectivity of 5.39 × 10¹² Jones, and a maximum external quantum efficiency of over 5000%. A 150-fold enhanced detectivity (2.33 × 10¹² Jones) was achieved under 635 nm light illumination in the optimized device. These results provide an alternative approach for improving the photoresponse of MoS₂ photodetectors.

Enhanced photocatalytic performance of Cu2O/MoS2/ZnO composites on Cu mesh substrate for nitrogen reduction

Cu₂O nanoparticles and MoS₂nanoflowers decorated with ZnO nanospheres were successfully co-deposited on Cu mesh via a mild electrodeposition method to build a dual direct Z-scheme heterostructure. The prepared materials can effectively synthesize ammonia with N₂and H₂O in the liquid membrane reactor under simulated visible light. The results indicate that 3D nanomaterials exhibit better performance compared to a pure semiconductor due to the synergistic effect of enhanced visible light absorption, longer photogenerated carrier lifetime and the specific charge transfer path of dual direct Z-scheme structure. Meanwhile, the hydrophilicity of Cu₂O/MoS₂/ZnO rapidly makes the surface of the catalyst wet when it participates in the photo reaction, which promotes the contact between the reactant and exciton. This work proposes the electron transfer and possible reaction mechanism corresponding to the designed catalyst, which can provide a reference for other photocatalytic applications using a semiconductor heterojunction as a catalyst.

MoS2 Based Photodetectors: A Review

Photodetectors based on transition metal dichalcogenides (TMDs) have been widely reported in the literature and molybdenum disulfide (MoS2) has been the most extensively explored for photodetection applications. The properties of MoS2, such as direct band gap transition in low dimensional structures, strong light-matter interaction and good carrier mobility, combined with the possibility of fabricating thin MoS2 films, have attracted interest for this material in the field of optoelectronics. In this work, MoS2-based photodetectors are reviewed in terms of their main performance metrics, namely responsivity, detectivity, response time and dark current. Although neat MoS2-based detectors already show remarkable characteristics in the visible spectral range, MoS2 can be advantageously coupled with other materials to further improve the detector performance Nanoparticles (NPs) and quantum dots (QDs) have been exploited in combination with MoS2 to boost the response of the devices in the near ultraviolet (NUV) and infrared (IR) spectral range. Moreover, heterostructures with different materials (e.g., other TMDs, Graphene) can speed up the response of the photodetectors through the creation of built-in electric fields and the faster transport of charge carriers. Finally, in order to enhance the stability of the devices, perovskites have been exploited both as passivation layers and as electron reservoirs.

Transparent and flexible ZnO nanorods induced by thermal dissipation annealing without polymer substrate deformation for next-generation wearable devices

The fabrication of a transparent and flexible ultraviolet photodetector based on hydrothermally grown ZnO nanorods requires an annealing step to render the sol–gel spin-coated ZnO seed layer crystalline. As high-temperature annealing deforms low-melting-point polymer substrates, we herein devised a thermal dissipation annealing (TDA) method in which heat transfer to ZnO thin films is synchronized with heat release from the polymer substrate to crystallize the ZnO seed layer without polymer substrate deformation and melting. ZnO nanorods (NRs) were hydrothermally grown on non-annealed and annealed ZnO seed layers, and NR density and diameter were shown to be higher in the latter case, as the crystallized ZnO seed layer provided heterogeneous nucleation sites for NR growth. In addition, the larger density and diameter of ZnO NRs grown on the annealed ZnO seed layer were confirmed by analysis of O 1s signal intensities. A transparent and flexible UV photodetector based on ZnO NRs grown on the annealed ZnO seed layer exhibited a higher photocurrent/dark current ratio, photosensitivity, and photoresponsivity than that fabricated using a non-annealed seed layer. Taken together, the above results suggest that the TDA method is an effective way of fabricating transparent and flexible UV photodetectors with high photosensitivity, photoresponsivity, and photocurrent stability and it means that the next generation wearable devices can be easily realized by using the TDA method.

A transparent and flexible ultraviolet (UV) photodetector based on ZnO nanorods grown onto the thermal dissipation annealed ZnO seed layer exhibited high photosensitivity, photoresponsivity, and photocurrent stability without substrate deformation.

Design and Integration of a Layered MoS2/GaN van der Waals Heterostructure for Wide Spectral Detection and Enhanced Photoresponse

Molybdenum disulfide (MoS₂) as a typical two-dimensional (2D) transition-metal dichalcogenide exhibits great potential applications for the next-generation nanoelectronics such as photodetectors. However, most MoS₂-based photodetectors hold obvious disadvantages including a narrow spectral response in the visible region, poor photoresponsivity, and slow response speed. Here, for the first time, we report the design of a two-dimensional MoS₂/GaN van der Waals (vdWs) heterostructure photodetector consisting of few-layer p-type MoS₂ and very thin n-type GaN flakes. Thanks to the good crystal quality of the 2D-GaN flake and the built-in electric field in the interface depletion region of the MoS₂/GaN p-n junction, photogenerated carriers can be rapidly separated and more excitons are collected by electrodes toward the high photoresponsivity of 328 A/W and a fast response time of 400 ms under the illumination of 532 nm light, which is seven times faster than pristine MoS₂ flake. Additionally, the response spectrum of the photodetector is also broadened to the UV region with a high photoresponsivity of 27.1 A/W and a fast response time of 300 ms after integrating with the 2D-GaN flake, exhibiting an advantageous synergetic effect. These excellent performances render MoS₂/GaN vdWs heterostructure photodetectors as promising and competitive candidates for next-generation optoelectronic devices.

A review of molybdenum disulfide (MoS2) based photodetectors: from ultra-broadband, self-powered to flexible devices

Two-dimensional transition metal dichalcogenides (2D TMDs) have attracted much attention in the field of optoelectronics due to their tunable bandgaps, strong interaction with light and tremendous capability for developing diverse van der Waals heterostructures (vdWHs) with other materials. Molybdenum disulfide (MoS2) atomic layers which exhibit high carrier mobility and optical transparency are very suitable for developing ultra-broadband photodetectors to be used from surveillance and healthcare to optical communication. This review provides a brief introduction to TMD-based photodetectors, exclusively focused on MoS2-based photodetectors. The current research advances show that the photoresponse of atomic layered MoS2 can be significantly improved by boosting its charge carrier mobility and incident light absorption via forming MoS2 based plasmonic nanostructures, halide perovskites-MoS2 heterostructures, 2D-0D MoS2/quantum dots (QDs) and 2D-2D MoS2 hybrid vdWHs, chemical doping, and surface functionalization of MoS2 atomic layers. By utilizing these different integration strategies, MoS2 hybrid heterostructure-based photodetectors exhibited remarkably high photoresponsivity raging from mA W-1 up to 1010 A W-1, detectivity from 107 to 1015 Jones and a photoresponse time from seconds (s) to nanoseconds (10-9 s), varying by several orders of magnitude from deep-ultraviolet (DUV) to the long-wavelength infrared (LWIR) region. The flexible photodetectors developed from MoS2-based hybrid heterostructures with graphene, carbon nanotubes (CNTs), TMDs, and ZnO are also discussed. In addition, strain-induced and self-powered MoS2 based photodetectors have also been summarized. The factors affecting the figure of merit of a very wide range of MoS2-based photodetectors have been analyzed in terms of their photoresponsivity, detectivity, response speed, and quantum efficiency along with their measurement wavelengths and incident laser power densities. Conclusions and the future direction are also outlined on the development of MoS2 and other 2D TMD-based photodetectors.

Synthesis of a Hybrid Nanostructure of ZnO-Decorated MoS2 by Atomic Layer Deposition

We introduce the synthesis of hybrid nanostructures comprised of ZnO nanocrystals (NCs) decorating nanosheets and nanowires (NWs) of MoS₂ prepared by atomic layer deposition (ALD). The concentration, size, and surface-to-volume ratio of the ZnO NCs can be systematically engineered by controlling both the number of ZnO ALD cycles and the properties of the MoS₂ substrates, which are prepared by sulfurizing ALD MoO₃. Analysis of the chemical composition combined with electron microscopy and synchrotron X-ray techniques as a function of the number of ZnO ALD cycles, together with the results of quantum chemical calculations, help elucidate the ZnO growth mechanism and its dependence on the properties of the MoS₂ substrate. The defect density and grain size of MoS₂ nanosheets are controlled by the sulfurization temperature of ALD MoO₃, and the ZnO NCs in turn nucleate selectively at defect sites on MoS₂ surface and enlarge with increasing ALD cycle numbers. At higher ALD cycle numbers, the coalescence of ZnO NCs contributes to an increase in areal coverage and NC size. Additionally, the geometry of the hybrid structures can be tuned by changing the dimensionality of the MoS₂, by employing vertical NWs of MoS₂ as the substrate for ALD ZnO NCs, which leads to improvement of the relevant surface-to-volume ratio. Such materials are expected to find use in newly expanded applications, especially those such as sensors or photodevices based on a p-n heterojunction which relies on coupling transition-metal dichalcogenides with NCs.