Highly Efficient Exciton Modulation in MoSe2/PdSe2 Heterostructures.

We report a pronounced ∼6-fold enhancement of room-temperature A-exciton emission in a type-I MoSe2/PdSe2 van der Waals heterostructure, yielding a photoluminescence quantum yield of 6%, as compared to ∼1% for as-exfoliated monolayer MoSe2. This unusual enhancement is accompanied by strong quenching of the B exciton, consistent with interlayer electronic coupling that redistributes exciton populations toward the radiative A-exciton channel. Power- and temperature-dependent measurements reveal a suppression of exciton-exciton annihilation and a crossover to quenched emission at a low temperature, indicating a redistribution of exciton relaxation pathways. Photoluminescence excitation spectroscopy further reveals a broadband enhancement spanning 450-725 nm. These results demonstrate that interlayer electronic coupling can be used as an efficient means to redirect exciton populations toward radiative channels, enhancing emission efficiency in two-dimensional semiconductors without chemical modification or significant strain.