We use angular-resolved photoluminescence excitation spectroscopy to probe energy relaxation towards the lowest lying states (k â̂¥=0) on the lower polariton branch (LPB) of two different strong-coupled J-aggregate organic semiconductor microcavities. We find that states along the upper polariton branch (UPB) are able to undergo efficient relaxation to populate states around kâ̂¥=0 on the LPB; a process that occurs through the rapid relaxation of UPB polaritons to the exciton reservoir. In contrast, LPB states having a photon fraction >0.5 are not apparently able to undergo further relaxation towards k â̂¥=0, constituting an effective relaxation bottleneck.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 30 Sep 2013|