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Photodetectors based on two-dimensional/three-dimensional (2D/3D) semiconducting heterostructures have attracted tremendous attention in recent years due to their novel performance. Here, we found that the photodetection performance of the graphene (Gr)/Si 2D/3D heterostructure can be very broadly enhanced by introducing an optimized ultrathin WS2 film prepared by sulfidation as an interfacial layer. The fabricated Gr/WS2(10.9 nm)/Si photodetector shows a wide spectralresponse from 400 to 1800 nm with a maximum photoresponsivity of 8.96 × 104 A W−1 and photodetectivity of 8.86 × 1011 Jones at 690 nm, which are more than three orders of magnitude higher than that of the Gr/Si photodetector. Such a high photoresponsivity can be attributed to the strong photogain induced by the hole trap states that exist in the WS2 film. With the increase in the WS2 film thickness, the photoresponsivity increases firstly owing to the increase of hole trap states, and then decreases due to the decrease in light transmittance through WS2. The device also shows a high responsivity of 0.735 A W−1 at 1550 nm by forming type-II interlayer excitation. Our results indicate that 2D transition metal dichalcogenides (TMDCs) could be a good candidate functioning as an interfacial layer for high performance Gr/Si photodetectors, which provide a facile way for enhancing the photodetection performance of van der Waals 2D/3D heterostructure photodetectors.

Semiconducting two-dimensional (2D) layered materials have shown great potential in next-generation electronics due to their novel electronic properties. However, the performance of field effect transistors (FETs) based on 2D materials is always environment-dependent and unstable under gate bias stress. Here, we report the environment-dependent performance and gate-induced instability of few-layer p-type WSe2-based FETs. We found that the hole mobility of the transistor drastically reduces in vacuum and further decreases after in situ annealing in vacuum compared with that in air, which can be recovered after exposure to air. The on-current of the WSe2 FET increases with positive gate bias stress time but decreases with negative gate bias stress time. For the double sweeping transfer curve, the transistor shows prominent hysteresis, which depends on both the sweeping rate and the sweeping range. Large hysteresis can be observed when a slow sweeping rate or large sweeping range is applied. In addition, such gate-induced instability can be reduced in vacuum and further reduced after in situ vacuum annealing. However, the gate-induced instability cannot be fully eliminated, which suggests both gases adsorbed on the device and defects in the WSe2 channel and/or the interface of WSe2/SiO2 are responsible for the gate-induced instability. Our results provide a deep understanding of the gate-induced instability in p-type WSe2 based transistors, which may shed light on the design of high-performance 2D material-based electronics.

Since the discovery of graphene in 2004, it has become a worldwide hot topic due to its fascinating properties. However, the zero band gap and weak light absorption of graphene strictly restrict its applications in optoelectronic devices. In this regard, semiconducting two-dimensional (2D) materials are thought to be promising candidates for next-generation optoelectronic devices. Infrared (IR) light has gained intensive attention due to its vast applications, including night vision, remote sensing, target acquisition, optical communication, etc. Consequently, the generation, modulation, and detection of IR light are crucial for practical applications. Due to the van der Waals interaction between 2D materials and Si, the lattice mismatch of 2D materials and Si can be neglected; consequently, the integration process can be achieved easily. Herein, we review the recent progress of semiconducting 2D materials in IR optoelectronic devices. Firstly, we introduce the background and motivation of the review. Then, the suitable materials for IR applications are presented, followed by a comprehensive review of the applications of 2D materials in light emitting devices, optical modulators, and photodetectors. Finally, the problems encountered and further developments are summarized. We believe that milestone investigations of IR optoelectronics based on 2D materials beyond graphene will emerge soon, which will bring about great industrial revelations in 2D material-based integrated nanodevice commercialization.

In this study, using gadolinium (Gd) as a dopant, Gd-WO3/Ag/Gd-WO3 (WGd–Ag–WGd) transparent conductive films with improved electrochromic (EC) and energy storage performance were fabricated on glass substrates by reactive sputtering. The EC performance and sheet resistance of WGd–Ag–WGd are shown to be sensitive to the concentration of the Gd dopant. The optimized structure for transparent conducting (TC) coating is obtained to be Gd-WO3 (52 nm)/Ag (12 nm)/Gd-WO3 (42 nm) with a luminous transmittance of 82.7% and a sheet resistance of 3.4 Ω sq−1 at a modest Gd doping concentration of 0.29 at%. Such a film (sample size of 1 cm × 3 cm) exhibits luminous transmittance modulation (ΔTlum = 49.6%), high coloration efficiency (71.4 cm2 C−1 at 633 nm), fast switching time (1.6 s for coloring and 3.2 s for bleaching time), and long-term cycling stability (2000 cycles) with an applied potential of ±1.0 V. By combining the film structure characterization and electrochemical analysis, such a decent performance can be attributed to the embedded island structured monoclinic Gd2O3 on the surface of WO3 which enhanced charge capacity and reaction kinetics compared with undoped amorphous WO3 films. Moreover, the WGd–Ag–WGd films showed superior capacitive capability with a maximum specific capacitance of 124.7 F g−1 at 2 A g−1, suggesting their potential application in electrochemical energy storage (ECES) devices.

Recently, due to the excellent and tunable optoelectrical properties, quasi-two-dimensional (quasi-2D) layered perovskites have attracted tremendous attention for next-generation optoelectronic devices. However, fabricating high-quality 2D perovskite films, especially with low trap density, is still a challenge. Here, we successfully incorporate different concentrations of FA and Cs cations (i.e. mixed cations) into the quasi-2D perovskites of (iBA)2(MA)3Pb4I13 (FA = formamidinium; iBA = iso-butylamine; MA = methylamine) to modulate their thin film qualities, improving their subsequently fabricated device performances. When configured into photodetectors on rigid substrates, the optimal mixed cation-incorporated (iBA)2(MA)3Pb4I13 perovskites exhibit impressive photodetection properties, which are comparable or even better than those of other 2D perovskite-based photodetectors previously reported. Once fabricated as a flexible photodetector on polyimide, the quasi-2D perovskite device demonstrates further improved performances, yielding a good responsivity of 400 mA W−1, a high detectivity up to 1.68 × 1012 Jones and fast response speeds (rise and decay time constants of 43 and 22 ms, respectively) under 532 nm illumination. Importantly, the obtained devices possess excellent mechanical flexibility and durability with photocurrent maintaining 82% of the initial value even after 9000 bending cycles. This work can provide valuable design guidelines of 2D perovskites to obtain high-performance flexible photodetectors for next-generation optoelectronics.

Rational design of active and stable bifunctional electrocatalysts for both hydrogen evolution and oxygen evolution reactions is critical for the realization of renewable energy technologies. Although direct growth of active two-dimensional (2D) nanosheets on the current collector is an effective method to improve the exposure of active sites, the inefficient electron transfer and weak electron interaction between 2D nanosheets and current collectors greatly limit their overall electrochemical performance. Herein, a unique sandwich structure of CoMnP/Ni2P/NiFe is successfully designed via introducing a Ni2P interlayer between CoMnP nanosheets and nickel–iron (NiFe) foam to achieve an excellent bifunctional electrocatalyst in alkaline media. The metallic Ni2P interlayer does not only improve the electron transfer from the current collector of NiFe foam to the catalyst of CoMnP, but also enhances the intrinsic activity of each active site via strong electron interaction. Electrochemical studies show that the resulting electrocatalyst exhibits superior electrocatalytic activity, such as giving a low cell voltage of only 1.48 V at 10 mA cm−2 stably for a long time when applied as both the cathode and anode in alkaline solutions. These results evidently indicate the superior electrochemical characteristics of this sandwich structure, which may provide a new insight into the design of electrocatalysts for different utilizations.

Due to their excellent physical and chemical properties, one-dimensional (1D) transparent metal-oxide nanostructures, especially nanowires (NWs), are widely considered to be promising candidates for next-generation high-performance electronics. Meanwhile, with increasing industrial demand for electronics which can reliably function in harsh environments, such as high humidity, high temperature, and robust operating environments, 1D metal-oxide nanostructures with wide bandgaps and high stabilities are attracting increasing interest for devices operating in extreme conditions. In this article, we provide a comprehensive review on the recent advances in high-performance transparent metal-oxide NWs and their corresponding device applications in harsh electronics. We begin with a brief introduction of different methodologies for the controllable synthesis of high-quality metal-oxide NWs, followed by an evaluation of the physical limitations of these nanomaterials and approaches for addressing their electrical contact issues. Importantly, the operating principles of transistors, photodetectors and gas sensors based on these 1D metal-oxide nanostructures as well as some excellent examples will be thoroughly discussed for harsh environment operation. The final section describes the challenges for the practical utilization of 1D metal-oxide nanostructures for industrial applications and concludes with an outlook on the future development of these NWs for harsh electronics.

van der Waals heterostructures built from two-dimensional (2D) materials have attracted wide attention because of their fascinating electrical and optoelectronic properties. Here, we report a highly responsive and broadband photodetector based on WS2–graphene van der Waals epitaxial heterostructures, which were fabricated by directly growing single crystalline few layer WS2 nanosheets on a polycrystalline graphene film. Upon light illumination, the current apparently reduces because of the transfer of photogenerated electrons from WS2 into the underlying p-type graphene and a photo-gating effect induced by the remaining holes, which is in stark contrast to ordinary semiconducting photoconductors. Thanks to the strong and broadband absorption of WS2, the WS2–graphene heterostructure photodetector exhibits a high responsivity with a maximum of 950 A W−1 at 405 nm and a wide spectrum response ranging from 340 to 680 nm. The high performance can be attributed to the internal built-in electric field at the WS2–graphene interface, which leads to the efficient separation of photogenerated electron–hole pairs. The WS2–graphene heterostructure photodetector may have potential applications in low cost, broadband, and flexible optoelectronics.

Two-dimensional (2D) materials have attracted wide attention due to their exotic properties. In particular, the lack of dangling bonds makes it possible to build highly lattice mismatched heterostructures composed of 2D materials and conventional semiconductors. Here, we report that by simply stacking a chemical vapor deposition grown monolayer WS2 film onto the surface of a room temperature sputtered ZnO film, significant enhanced ultra-violet (UV) photoresponse can be achieved. In this heterostructure of ZnO–WS2, the ZnO film acts as a light harvesting layer while the WS2 monolayer functions as a carrier transport layer which facilitates the photocarrier transport and reduces its recombination. Such a mechanism was confirmed by the observation of further photoresponsivity improvement of the ZnO–WS2 heterostructure under vacuum which removes the surface absorbates and thereby increases the carrier mobility of WS2. The strategy presented here can be applied to other wide band-gap semiconductors, shedding light on high sensitivity and flexible UV photodetectors based on van der Waals heterostructures.

Single-crystalline GeS nanoribbons were synthesized by chemical vapor deposition for the first time. Structural characterization revealed that the nanoribbons grow along the [01] direction with a thickness of 20–50 nm, a width of several micrometers and a length of hundreds of micrometers. The GeS nanoribbons show a p-type behavior verified from the field effect transport measurement. The nanoribbon photodetectors respond to the entire visible incident light with a response edge at around 750 nm consistent with the band gap absorption of GeS. A strong nonlinear light-intensity-dependent response was observed between the measured illumination intensity from 0.25 to 212 μW cm−2. Under 530 nm light illumination, the maximum responsivity and external quantum efficiency are 139.9 A W−1 and 32730%, respectively. These results indicate that GeS nanoribbon is a promising semiconducting nanomaterial for high performance broadband visible-light sensing applications.

We demonstrate the synthesis of large-area monolayer WS2 films by chemical vapor deposition (CVD) and investigate their photoresponse properties by fabricating n-type field effect transistors (FETs) with Al as the ohmic contact. Our CVD-grown monolayer WS2 shows an electron mobility of 0.91 cm2 V−1 s−1 and an ON/OFF ratio of 106, indicating its comparable electronic properties to the mechanically exfoliated flake sample. In a vacuum, by applying a gate bias (60 V), the responsivity of the monolayer WS2 phototransistor can increase up to 18.8 mA W−1 and a decent sub-second level response time can be maintained. In contrast, in air, it shows a very fast response time of less than 4.5 ms, but at the cost of responsivity reduction to 0.2 μA W−1. Such a distinctive ambient-sensitive photo-detecting performance can be well-explained by the pronounced effect of charge-acceptor-like O2/H2O molecule adsorption/desorption on the photocarrier transport. Our CVD-grown high quality monolayer WS2 may pave the way for developing industrial-scale optoelectronic devices for photo-detecting and chemical sensing applications.

ZnS nanocombs were fabricated via a two-step growth method. By annealing Au coated ZnS nanobelts with the help of SnO2/C, comb-like nanostructures would be formed. In the absence of SnO2/C, Au coated ZnS nanobelts would be evaporated completely at the same temperature. As revealed by high resolution transmission microscopy, the growth direction of the ZnS nanobelts was [210] while that of the branches was [001], which epitaxially grew on the (00 ± 1) side surfaces of the ZnS nanobelts. Self-evaporation was used to explain the formation of the ZnS nanocombs. Photoluminescence spectrum reveals that the ZnS nanocombs had two emission bands at 570 and 635 nm.

Correction for ‘Large-area synthesis of monolayer WS2 and its ambient-sensitive photo-detecting performance’ by Changyong Lan et al., Nanoscale, 2015, 7, 5974–5980.

String-like ZnS/SnO nanowire/nanosheet hierarchical nanoheterostructures were synthesized by a two-stage vapor transport and condensation method. X-Ray diffraction, scanning electron microscopy, and transmission electron microscopy were used to characterize and analyze the as-synthesized products. The results indicated that the synthesized products consisted of numerous rectangular single crystalline SnO nanosheets threaded by single crystalline ZnS nanowires. A growth mechanism for the growth of the string-like nanoheterostructures has been proposed. Room temperature photoluminescence properties of the nanostructures were investigated. Both the emissions from ZnS nanowires and SnO nanosheets were observed in the PL spectrum of the string-like nanoheterostructures. These special heterostructures may find applications in nanoelectronic and photonic devices.