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) was introduced onto the fluorene bridge of 4,4'-(9H-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, 45.5 lm W), which are higher than the device employed DTAF (without SiPh groups) (11.6%, 35.3 cd A, 41.3 lm W) 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.

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A spiro-configured bipolar molecule (CSC) that possesses high triplet energy, suitable energy levels, and balanced ambipolar carrier mobilities was successfully applied as an efficient host material, compatible with various iridium-based green phosphors, to realize highly efficient single-layer PhOLEDs of a maximum external quantum efficiency up to 8.3% (31.4 cd A(-1)) at a practical brightness of 1000 cd m(-2) (8 V).

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