wanglin

Abstract

Two-dimensional (2D) transition metal dichalcogenide (TMDC) monolayers, a class of ultrathin materials with a direct bandgap and high exciton binding energies, provide an ideal platform to study the photoluminescence (PL) of light-emitting devices. Atomically thin TMDCs usually contain various defects, which enrich the lattice structure and give rise to many intriguing properties. As the influences of defects can be either detrimental or beneficial, a comprehensive understanding of the internal mechanisms underlying defect behaviour is required for PL tailoring. Herein, recent advances in the defect influences on PL emission are summarized and discussed. Fundamental mechanisms are the focus of this review, such as radiative/nonradiative recombination kinetics and band structure modification. Both challenges and opportunities are present in the field of defect manipulation, and the exploration of mechanisms is expected to facilitate the applications of 2D TMDCs in the future.

Abstract

The emerging micro-nano-processing technologies have propelled significant advances in multifunctional systems that can perform multiple functions within a small volume through integration. Herein, we present an on-chip multifunctional system based on a 1T/2H-MoS₂/graphene fishnet tube, where a micro-supercapacitor and a gas sensor are integrated. A hybrid three-dimensional stereo nanostructure, including MoS₂ nanosheets and graphene fishnet tubes, provides K⁺ ions with a short diffusion pathway and more active sites. Owing to the large layer spacing of 1T-MoS₂ promoting fast reversible diffusion, the on-chip micro-supercapacitor exhibits excellent electrochemical properties, including an areal capacitance of 0.1 F·cm⁻² (1 mV·s⁻¹). The variation in the conductivity of 2H-MoS₂ when ammonia molecules are adsorbed as derived from the first-principles calculations proves the Fermi level-changes theory. Driven by a micro-supercapacitor, the responsivity of the gas sensor can reach 55.7% at room temperature (27 °C). The multifunctional system demonstrates the possibility of achieving a two-dimensional integrated system for wearable devices and wireless sensor networks in the future.

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