Exciton-exciton annihilation in organic polariton microcavities

Abstract

We investigate the incoherent diffusion of excitons in thin films ($5.1\ifmmode\pm\else\textpm\fi{}0.1\text{ }\text{nm}$ thick) of a highly absorbing J-aggregated cyanine dye material (${10}^{6}\text{ }{\text{cm}}^{\ensuremath{-}1}$ absorption constant) as the excitonic component of a polariton microcavity. Under high-intensity pulsed laser excitation, the J-aggregated molecular films exhibit significant exciton-exciton annihilation, indicating a large exciton diffusion radius of more than 100 nm. When the material is strongly coupled to a cavity, the polaritonic structure also shows exciton-exciton annihilation, which is a competing process against the establishment of a threshold population of polaritons needed for polariton lasing. This study suggests that exciton-exciton annihilation is a loss process which can significantly increase the lasing threshold in polariton microcavities.