Exciton Diffusion and Annihilation in Nanophotonic Purcell Landscapes

摘要

Excitons spread through diffusion and interact through exciton–excitonannihilation. Nanophotonics can counteract the resulting decrease in lightemission. However, conventional enhancement treats emitters as immobileand non-interacting. It neglects exciton redistribution between regions withdifferent enhancements and the increase in non-radiative decay at high excitondensities. Here, the authors went beyond the localized Purcell effect to exploitexciton dynamics and turn their typically detrimental impact into additionalemission. As interacting excitons diffuse through optical hotspots, the balanceof excitonic and nanophotonic properties leads to either enhanced or suppressedphotoluminescence. The dominant enhancement mechanisms areidentified in the limits of high and low diffusion and annihilation. Diffusionlifts the requirement of spatial overlap between excitation and emissionenhancements, which are harnessed to maximize emission from highly diffusiveexcitons. In the presence of annihilation, improved enhancement is predictedat increasing powers in nanophotonic systems dominated by emissionenhancement. The guidelines are relevant for efficient and high-power lightemittingdiodes and lasers tailored to the rich dynamics of excitonic materialssuch as monolayer semiconductors, perovskites, or organic crystals.