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.
Convenient generation of stable superatomic silver clusters and their systematic site-specific tailoring and directional assembly present an enduring and significant challenge. In this work, we prepared a face-centered cubic (fcc) array of Ag superatoms protected by face-capping 1,2-dithiolate-o-carborane (CBHS) ligands, each produced from 1-thiol-o-carborane in crystallization with simultaneous reduction of Ag to Ag. We find that the corner N-donor ligands contribute predominately to the stability and luminescence of the Ag superatom. As the first-formed nanocluster [Ag(CBHS)(CHCN)]·4CHCN (NC-1) with labile vertex-coordinated CHCN ligands is highly unstable, monodendate pyridine ligands were used to replace these CHCN species site-specifically, giving [Ag(CBHS)(pyridine/p-methylpyridine)] (NCs-2,3) in gram scale with its core structure intact, which features ultrastability up to 150 °C in air. Moreover, using bidentate N-containing ligands to bridge the superatomic Ag building blocks, we constructed an unprecedented hierarchical series of 1D-to-3D superatomic silver cluster-assembled materials (SCAM-1,2,3,4), and SCAM-4 is air-stable up to 220 °C. Furthermore, this series of stable solid-state superatomic-nanocluster materials exhibit tunable dual emission with wide-range thermochromism. The present study constitutes a major step toward the development of ligand-modulation of the structure, stability, assembly, and functionality of superatomic silver nanoclusters.
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.
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