Remote Steric Effect as a Facile Strategy for Improving the Efficiency of Exciplex-Based OLEDs

This work reports a new strategy of introducing remote steric effect onto the electron donor for giving the better performance of the exciplex-based organic light-emitting device (OLED). The bulky triphenylsilyl group (SiPh 3 ) was introduced onto the fluorene bridge of 4,4′-(9 H -fluorene-9,9-diyl)bis( N, N -di- p -tolylaniline) (DTAF) to create remote steric interactions for increasing the possibility of effective contacts between electron-donating chromophores and acceptor molecules, rendering the resulting exciplex to have a higher photoluminescence quantum yield (PLQY). The green exciplex device based on DSDTAF:3N-T2T (1:1) as an emitting layer exhibits a low turn-on voltage of 2.0 V, high maximum efficiencies (13.2%, 42.9 cd A –1, 45.5 lm W –1 ), which are higher than the device employed DTAF (without SiPh 3 groups) (11.6%, 35.3 cd A –1, 41.3 lm W –1 ) as donor under the same device structure. This strategy was further examined for blue exciplex, where the EQE was enhanced from 9.5% to 12.5% as the electron acceptor PO-T2T mixed with a tert -butyl group substituted carbazole-based donor (CPTBF) as the emitting exciplex in device. This strategy is simple and useful for developing high performance exciplex OLEDs.