Exciton diffusion and annihilation in nanophotonic Purcell landscapes

Excitons spread through diffusion and interact through exciton-exciton annihilation. Nanophotonics can counteract the resulting decrease in light emission. However, conventional enhancement treats emitters as immobile and noninteracting. Here, we go beyond the localized Purcell effect to exploit exciton dynamics. As interacting excitons diffuse through optical hotspots, the balance of excitonic and nanophotonic properties leads to either enhanced or suppressed photoluminescence. We identify the dominant enhancement mechanisms in the limits of high and low diffusion and annihilation to turn their detrimental impact into additional emission. Our guidelines are relevant for efficient and high-power light-emitting diodes and lasers based on monolayer semiconductors, perovskites, or organic crystals.