Predicting plasmonic enhancement of photoluminescence with a multi-scale and multi-physics numerical method

Abstract

Monolayer transition-metal dichalcogenides (TMDs) are promising ultrathin light emitters, but their intrinsically weak light–matter interaction limits achievable radiative efficiency, motivating the use of plasmonic nanostructures to enhance photoluminescence (PL) and electroluminescence (EL). While extensive experimental work has established that such enhancement arises from a combination of near-field excitation enhancement, Purcell-accelerated radiative decay, and charge-transfer-driven exciton/trion redistribution, no existing numerical framework self-consistently couples all three underlying physical timescales to directly predict the resulting emission spectra. Here, we develop a multiscale simulation framework that couples a finite-difference time-domain (FDTD) electromagnetic solver, a semiconductor drift-diffusion transport model, and bright/dark exciton rate equations through an operator-splitting outer loop. Cycle-averaged optical generation rates and Purcell-renormalized radiative lifetimes extracted from the electromagnetic layer drive the exciton population dynamics, which in turn source an incoherent dipole emission current that re-enters the electromagnetic solver. For bare monolayer MoS2 and WSe2, we find that the ∼9-fold difference in peak PL intensity substantially overstates the true emission contrast: once linewidth and population dynamics are accounted for via the total time-integrated PL, WSe2 emits only ∼5.3 times more strongly than MoS2 under identical illumination. Applied to MoS2 coupled to a periodic Au grating, the framework predicts a ∼35-fold PL enhancement, arising from competing effects: a two-orders-of-magnitude gain in bright-exciton population offset by a five-fold reduction in internal quantum yield due to metal-induced non-radiative quenching. This enhancement is accompanied by a Purcell-accelerated population buildup time, which is qualitatively consistent with experimentally measured lifetime reductions in analogous plasmonic geometries. The framework further reproduces the strong polarization dependence intrinsic to plasmonic gratings, showing enhancement only for the polarization supporting localized surface plasmon resonances. These results establish a predictive, self-consistent multiphysics tool for the rational design of plasmonically enhanced light emitters from two-dimensional materials.