Nanoscale Interface Engineering of Exciton Dynamics in Monolayer MoSe2 through Ground-State Charge Transfer for Ultrafast Optoelectronics

Abstract

Interfacial charge transfer provides an effective route for nanoscale interface engineering of the electronic and optical properties of atomically thin two-dimensional semiconductors without chemical modification or electrostatic gating. Here, we investigate the influence of ground-state interfacial charge transfer on exciton dynamics in monolayer MoSe2 using photoluminescence spectroscopy and ultrafast transient absorption measurements. An atomically thin MoSe2/α-MoO3 van der Waals heterostructure is compared with a hexagonal BN (hBN)-supported control sample, where no ground-state charge transfer is expected. Photoluminescence measurements reveal that the emission intensity of the same monolayer MoSe2 flake decreases by approximately a factor of 10 after transfer from the poly(dimethylsiloxane) substrate onto MoO3, substantially larger than the 2.5-fold reduction observed after transfer onto hBN. Transient absorption measurements show that the exciton lifetime is markedly shortened in the MoO3-supported sample. In addition, the pronounced excitation-density dependence associated with exciton–exciton annihilation in MoSe2/hBN is largely suppressed in MoSe2/MoO3. These observations are attributed to resident holes introduced by charge transfer from MoSe2 to MoO3, which provide an efficient nonradiative recombination pathway through exciton–hole interactions. No evidence for long-lived interlayer excitons is observed, indicating that the primary role of the MoO3 substrate is to modify exciton dynamics through ground-state charge transfer rather than long-lived charge separation. These results establish interfacial charge transfer as a simple and effective strategy for engineering exciton dynamics in atomically thin semiconductors and van der Waals heterostructures, providing opportunities for ultrafast optoelectronic and photonic devices.