Exciplex-forming derivatives of 2,7-di-tert-butyl-9,9-dimethylacridan and benzotrifluoride for efficient OLEDs

Abstract Strongly medium dependent capability to exhibit not only prompt/delayed thermally-activated fluorescence but also aggregation-induced phosphorescence or exciplex emission is demonstrated either for solutions or for solid samples of acridan-based luminophores. Multicolour emissions of different nature were detected and studied for donor-acceptor derivatives of 2- or 4-(trifluoromethyl)benzene and 2,7-di-tert-butyl-9,9-dimethylacridine containing trifluoromethyl groups in ortho and para positions. For the demonstration of one of possible applications, both compounds were tested in the emissive layers of exciplex-based OLEDs. In the best case, their high maximum current, power and external quantum efficiences of 29.5 cd/A, 29.1 lm/W and 8.2% respectively were achieved for the device based on exciplex electroluminescence resulting from recombination of intermolecular charge transfer states formed on the interface of electron-donating and electron-accepting molecules used.