Probe exciplex structure of highly efficient thermally activated delayed fluorescence organic light emitting diodes.

ABSTRACT: The lack of structural information impeded the access of efficient luminescence for the exciplex type thermally activated delayed fluorescence (TADF). We report here the pump-probe Step-Scan Fourier transform infrared spectra of exciplex composed of a carbazole-based electron donor (CN-Cz2) and 1,3,5-triazine-based electron acceptor (PO-T2T) codeposited as the solid film that gives intermolecular charge transfer (CT), TADF, and record-high exciplex type cyan organic light emitting diodes (external quantum efficiency: 16%). The transient infrared spectral assignment to the CT state is unambiguous due to its distinction from the local excited state of either the donor or the acceptor chromophore. Importantly, a broad absorption band centered at ~2060?cm-1 was observed and assigned to a polaron-pair absorption. Time-resolved kinetics lead us to conclude that CT excited states relax to a ground-state intermediate with a time constant of ~3?µs, followed by a structural relaxation to the original CN-Cz2:PO-T2T configuration within ~14?µs.

SUBMITTER: Lin TC 

PROVIDER: S-EPMC6079109 | biostudies-literature | 2018 Aug

REPOSITORIES: biostudies-literature