Electrical Control of Excitons in Bare MoSe2 and MoSe2/NbSe2 Heterostructures.

Monolayer transition metal dichalcogenides (TMDCs) are promising materials for next-generation optoelectronic devices owing to their strong excitonic responses and atomic thickness. Controlling their light emission electrically is a crucial step toward realizing practical nanoscale optoelectronic devices, such as light-emitting diodes and optical modulators. However, photoluminescence (PL) quenching in van der Waals TMDC/metal heterostructures, caused by ultrafast interlayer charge or energy transfer, impedes such electrical modulation. Here, we investigate monolayer MoSe2/bulk NbSe2 heterostructures and demonstrate that a vertical electric field tunes the PL intensity by nearly 3 orders of magnitude in bare MoSe2 and by about 1 order of magnitude in the MoSe2/NbSe2 heterostructure. First-principles calculations with spin-orbit coupling reveal stronger electronic coupling and band hybridization in the MoSe2/NbSe2 heterostructure than in conventional graphene-based counterparts. This enhances the sensitivity to a perpendicular electric field and enables a transition between direct and indirect bandgaps, strongly affecting the photoluminescence response. Unlike bare MoSe2, the heterostructure exhibits a pronounced thermal dependence of the enhancement factor, implying that the exciton lifetime dominates over interfacial transfer processes. Our findings demonstrate reversible, electric-field-driven PL control at a TMDC/metal interface, providing a pathway to electrically tunable light emission and improved contact engineering in two-dimensional optoelectronic devices.