Thermally-activated delayed fluorescence in polymer-small molecule exciplex blends for solution-processed organic light-emitting diodes.

The photophysics of an exciplex state, formed between a small molecule and a polymer, is investigated in this work. The results obtained with this blend show the strong potential of polymer-small molecule blends for triplet harvesting in organic light emitting diodes (OLEDs) via thermally-activated delayed fluorescence. The exciplex formed between poly(N-vinylcarbazole) (PVK) and 2,4,6-tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine (PO-T2T) shows yellow-green emission and is applied in solution processed OLEDs. The excellent film forming properties in this blend allow easy spin-coating and potential use in other solution-processing techniques, such as slot die coating. In this work we critically address the reverse intersystem crossing mechanism in the presented exciplex system, including the role of the local triplet state. Moreover, we bring a clear physical meaning to the exciplex emission decay components, including the decay occurring in a power-law fashion that is often ignored in the literature