As a direct-band-gap transition metal dichalcogenide (TMD), atomic thin MoS has attracted extensive attention in photodetection, whereas the hitherto unsolved persistent photoconductance (PPC) from the ungoverned charge trapping in devices has severely hindered their employment. Herein, we demonstrate the realization of ultrafast photoresponse dynamics in monolayer MoS by exploiting a charge transfer interface based on surface-assembled zinc phthalocyanine (ZnPc) molecules. The formed MoS/ZnPc van der Waals interface is found to favorably suppress the PPC phenomenon in MoS by instantly separating photogenerated holes toward the ZnPc molecules, away from the traps in MoS and the dielectric interface. The derived MoS detector then exhibits significantly improved photoresponse speed by more than 3 orders (from over 20 s to less than 8 ms for the decay) and a high responsivity of 430 A/W after AlO passivation. It is also demonstrated that the device could be further tailored to be 2-10-fold more sensitive without severely sacrificing the ultrafast response dynamics using gate modulation. The strategy presented here based on surface-assembled organic molecules may thus pave the way for realizing high-performance TMD-based photodetection with ultrafast speed and high sensitivity.

In this review, we present an in-depth discussion of the state-of-the-art doping engineering and functionalization of 2D metal chalcogenides for finely tuned material properties and functions in numerous application fields.

Ferroelectric engineered pn doping in two-dimensional (2D) semiconductors hold essential promise in realizing customized functional devices in a reconfigurable manner. Here, we report the successful pn doping in molybdenum disulfide (MoS 2 ) optoelectronic device by local patterned ferroelectric polarization, and its configuration into lateral diode and npn bipolar phototransistors for photodetection from such a versatile playground. The lateral pn diode formed in this way manifests efficient self-powered detection by separating ~12% photo-generated electrons and holes. When polarized as bipolar phototransistor, the device is customized with a gain ~1000 by its transistor action, reaching the responsivity ~12 A W −1 and detectivity over 10 13 Jones while keeping a fast response speed within 20 μs. A promising pathway toward high performance optoelectronics is thus opened up based on local ferroelectric polarization coupled 2D semiconductors.

As an emerging two-dimensional semiconductor, Bi 2 O 2 Se has recently attracted broad interests in optoelectronic devices for its superior mobility and ambient stability, whereas the diminished photoresponse near its inherent indirect bandgap (0.8 eV or λ = 1550 nm) severely restricted its application in the broad infrared spectra. Here, we report the Bi 2 O 2 Se nanosheets based hybrid photodetector for short wavelength infrared detection up to 2 μm via PbSe colloidal quantum dots (CQDs) sensitization. The type II interfacial band offset between PbSe and Bi 2 O 2 Se not only enhanced the device responsivity compared to bare Bi 2 O 2 Se but also sped up the response time to ∼4 ms, which was ∼300 times faster than PbSe CQDs. It was further demonstrated that the photocurrent in such a zero-dimensional−two-dimensional hybrid photodetector could be efficiently tailored from a photoconductive to photogate dominated response under external field effects, thereby rendering a sensitive infrared response >10 3 A/W at 2 μm. The excellent performance up to 2 μm highlights the potential of field-effect modulated Bi 2 O 2 Se-based hybrid photodetectors in pursuing highly sensitive and broadband photodetection.

Broadband photodetectors based on TiO 2 nanotubes (NTs) array have significant prospects in many fields such as environmental monitoring. Herein, a simple spin-coating process is successfully adopted to incorporate MAPbI 3 quantum dots (QDs) onto the surface of TiO 2 NTs to form a heterostructure, extending the response range of TiO 2 NT from ultraviolet to visible. Compared with pure TiO 2 NTs, the heterostructure demonstrates an improvement of responsivity in visible range by three orders of magnitude, and maintains its response performance in the UV range simultaneously. The TiO 2 NTs based heterostructure photodetectors demonstrate a relative fast and stable response in the 300-800 nm range and even have a reponsivity of 0.2 A W −1 at 700 nm. The photoelectric performance of the hybrid photodetector based on TiO 2 NTs maintains well when exposed to moist air for 72 h or heated from room temperature to 100 °C. Moreover, such a TiO 2 NTs/MAPbI 3 QDs heterostructure device demonstrates excellent flexibility and high transparency (85%) in the 400-800 nm range, their photodetecting performance is well retained after 200 cycles of repeated bending at 90°. The present strategy that combines facile electrospinning and solution-processed QDs may open a new avenue for wide range response and flexible devices construction.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201703115.superior photoelectric performance for photovoltaic [9] and photocatalytic [10] applications resulted from improved charge collection efficiency by promoting carrier separation and charge transport. [11][12][13] Recently, TiO 2 NTs array is applied for photodetecting applications primarily due to its high surface-to-volume ratios, which can increase the contact area with oxygen, and the controllable properties by varying dimensions of NTs. [14] However, as a wide band gap (anatase, 3.2 eV; rutile, 3.0 eV) semiconductor, anatase TiO 2 NTs only have absorption in the UV region if directly applied, which limits their photodetecting application in the wide range. [15] Many efforts have been thus devoted in the chemical doping and sensitization of TiO 2 in the past for its sensitivity in the visible spectra. Doping of TiO 2 with carbon, nitrogen, or transition metals tends to reduce the band gap of TiO 2 , whereas the 1D morphologies of resulted nanostructures are hardly maintained. [16] Alternatively filling the NTs with organic dye or polymer, which have a wide absorption range. [17] Nonetheless, the process for doping TiO 2 NTs could not be well controlled, [18] and the process of filling organic into the NTs is pretty complex and the thermal stability is poor for organics. Therefore, achieving wide range photodetecting over an inherent energy band gap of NTs without inducing fatal degradation of other photoelectronic performance is still a challenge. [19] Perovskite (CH 3 NH 3 PbI 3 , MAPbI 3 ) quantum dots (QDs), with the merits of size tunable band gap (from 3.1 to 1.7 eV), hi...

Van der Waals (vdW) dielectrics such as hBN are widely used to preserve the intrinsic properties of twodimensional (2D) semiconductors and support the fabrication of high-performance 2D devices. This is fundamentally attributed to their dangling-bond-free surface, carrying far lower density of charged scattering sources and trap states with respect to the conventional dielectrics (SiO 2 etc.). However, their wafer-scale fabrication and compatible integration with 2D semiconductors remain cumbersome, giving rise to the di culties in scalable fabrication of high-performance 2D devices. Here we report a high-κ vdW dielectric (ε r =11.5) composed of inorganic molecular crystal (IMC) Sb 2 O 3 , allowing for large-scale fabrication and facile integration via standard thermal evaporation process thanks to its particular crystal structure. Similarly, our vdW dielectric also supports remarkably improved 2D devices with respect to the typical conventional dielectric SiO 2 . The monolayer MoS 2 eld effect transistors (FET) supported by our vdW dielectric exhibits high on/off ratio (10 8 ), greatly enhanced electron mobility (from 20 to 80 cm 2 /Vs) and reduced transfer-curve hysteresis over an order of magnitude. Our results may open a new avenue towards compatible fabrication of vdW dielectrics using IMCs and lead to the scalable fabrication of high-performance 2D devices.

ZnO nanostructure‐based photodetectors have a wide applications in many aspects, however, the response range of which are mainly restricted in the UV region dictated by its bandgap. Herein, UV–vis–NIR sensitive ZnO photodetectors consisting of ZnO nanowires (NW) array/PbS quantum dots (QDs) heterostructures are fabricated through modified electrospining method and an exchanging process. Besides wider response region compared to pure ZnO NWs based photodetectors, the heterostructures based photodetectors have faster response and recovery speed in UV range. Moreover, such photodetectors demonstrate good flexibility as well, which maintain almost constant performances under extreme (up to 180°) and repeat (up to 200 cycles) bending conditions in UV–vis–NIR range. Finally, this strategy is further verified on other kinds of 1D nanowires and 0D QDs, and similar enhancement on the performance of corresponding photodetecetors can be acquired, evidencing the universality of this strategy.

By exploiting novel transport phenomena such as ion selectivity at the nanoscale, it has been shown that nanochannel systems can exhibit electrically controllable conductance, suggesting their potential use in neuromorphic devices. However, several critical features of biological synapses, particularly their conductance modulation, which is both memorable and gradual, have rarely been reported in these types of systems due to the fast flow property of typical inorganic electrolytes. In this work, we demonstrate that electrically manipulating the nanochannel conductance can result in nonvolatile conductance tuning capable of mimicking the analog behavior of synapses by introducing a room-temperature ionic liquid (IL) and a KCl solution into the two ends of a nanochannel system. The gradual conductance-tuning mechanism is identified through fluorescence measurements as the voltage-induced movement of the interface between the immiscible IL and KCl solution, while the successful memorization of the conductance tuning is ascribed to the large viscosity of the IL. We applied a nanochannel-based synapse to a handwritten digit-recognition task, reaching an accuracy of 94%. These promising results provide important guidance for the future design of nanochannel-based neuromorphic devices and the manipulation of nanochannel transport for computing.