Defect-Mediated Interlayer Charge Transfer and Prolonging Radiative Lifetime in Porous h-BN Fiber-Encapsulated MoS ₂ Heterojunctions

Semiconductor heterojunctions composed of stacked two-dimensional (2D) materials hold great promise for electronics and optoelectronic devices. Hexagonal boron nitride (h-BN) serves as the encapsulation layer that enhances the optical properties of heterojunctions by suppressing interfacial charge scattering and enabling quantum-confined energy transfer. Nevertheless, a mechanistic understanding of the modulation effect of interlayer coupling and interfacial charge dynamics in these heterostructures remains insufficient. Here, we report the in situ growth of ultrathin MoS₂ flakes encapsulated within porous h-BN fibers and construct high-quality h-BN/MoS₂ heterojunctions, demonstrating defect-mediated interactions and tunable optoelectronic properties. The cross-sectional architecture with the encapsulating sites in porous h-BN confirmed intimate interlayer contact, and investigations via femtosecond transient reflectance spectroscopy revealed the exciton radiative lifetime and defect-mediated charge transfer in the heterojunctions. The photoexcited carriers transfer between long-lived defect states in h-BN and the MoS₂, which induces the defect-related PL quenching in h-BN and prolonged radiative lifetime of MoS₂ excitons by 3-fold. This was attributed to defect-mediated charge transfer in MoS₂ and the dielectric screening from h-BN. This work elucidates the critical role of defect-engineered interfacial charge transfer in h-BN/MoS₂ heterostructures, offering valuable insights for advancing optoelectronic devices based on 2D heterojunctions.