# Electrical Control of Excitons in Bare-MoSe2 and MoSe2/NbSe2 Heterostructure

## TL;DR

This study demonstrates reversible electrical control of photoluminescence in monolayer MoSe2 and MoSe2/NbSe2 heterostructures, enabling tunable light emission for advanced nanoscale optoelectronic devices.

## Contribution

It reveals that electric fields can modulate PL intensity significantly and induce a direct-indirect bandgap transition, advancing electrical control in TMDC-based optoelectronics.

## Key findings

- Electric fields recover up to 80% of PL in heterostructures.
- PL intensity can be tuned by nearly three orders of magnitude.
- Electric-field-induced bandgap transition from direct to indirect.

## Abstract

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 towards 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 can effectively recover the PL intensity up to ~ 80% of bare-MoSe2. Furthermore, our analysis reveals that the room temperature PL intensity can be tuned by nearly three orders of magnitude in bare-MoSe2 and by about one order of magnitude in MoSe2/NbSe2 heterostructures. First-principles calculations incorporating spin-orbit coupling reveal that the perpendicular electric fields drive a transition from a direct to an indirect bandgap, fundamentally altering the optical response in the heterostructure. Unlike bare-MoSe2, the heterostructure exhibits a pronounced thermal dependence of the enhancement factor, implying that 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.