Interface Engineering for Efficient Photocarrier Generation and Transfer in Strongly Coupled Metallic/Semiconducting 1T'/2H MoS2 Heterobilayers.

Abstract

Developing alternative two-dimensional (2D) metallic/semiconducting (M/S) van der Waals heterostructures (vdWHs) along with an understanding of interfacial photocarrier behavior is crucial for designing high-performance optoelectronic devices. Here, we comprehensively explored the photophysical model of photocarrier generation and interfacial transfer in as-grown 2D 1T'/2H MoS₂ vdWHs using various spectroscopic characterizations. We demonstrated the transitions of activated photocarrier transfer trajectories by tuning the pump photon energies across the 2H MoS₂ bandgap. The importance of confined bilayer transfer systems and strong interlayer coupling at vdW interfaces for transfer efficiency was elucidated. Additionally, the fluorophlogopite substrate was found to be an external method for regulating photocarrier generation in individual 2H layers through the p-doping effect at the substrate-2H layer interfaces, and this influence was alleviated after introducing the 2H-1T' vdW interface. Particularly, 1T' MoS₂ as a broadband hot carrier absorber enabled the ultrafast (∼133 fs) injection and extraction of energetic hot carriers into the 2H layer via a photothermionic emission mechanism, achieving a high efficiency of ∼41% under 900 nm photoexcitation at room temperature. Our work offers fundamental insights into the complex interfacial carrier photophysics in 2D M/S vdWHs, providing a way of constructing advanced multifunctional devices by using these emerging materials as active components and interface engineering.