Theory of Energy Transfer in Organic Nanocrystals

TL;DR

This paper presents a new theoretical model for energy transfer in organic nanocrystals that explains experimental results without relying on exciton polaritons, using weak-coupling interactions and electromagnetic simulations.

Contribution

It introduces an alternative weak-coupling model that accurately reproduces experimental fluorescence data and predicts efficient energy transfer at very low acceptor densities.

Findings

Model matches fluorescence lifetime and spectrum measurements.

Predicts dominant acceptor emission at much lower densities.

Provides design guidelines for nanocrystal configurations.

Abstract

Recent experiments have shown that highly efficient energy transfer can take place in organic nanocrystals at extremely low acceptor densities. This striking phenomenon has been ascribed to the formation of exciton polaritons thanks to the photon confinement provided by the crystal itself. We propose an alternative theoretical model that accurately reproduces fluorescence lifetime and spectrum measurements in these systems without such an assumption. Our approach treats molecule-photon interactions in the weak-coupling regime, and describes the donor and acceptor population dynamics by means of rate equations with parameters extracted from electromagnetic simulations. The physical insight and predictive value of our model also enables us to propose nanocrystal configurations in which acceptor emission dominates the fluorescence spectrum at densities orders of magnitude lower than the experimental ones.