Efficient electroluminescent hybridized local and charge-transfer host materials with small singlet-triplet splitting to enhance exciton utilization efficiency: excited state transition configuration.

A series of efficient electroluminescent materials with dual carrier transport properties shows enhanced singlet exciton utilization ( ) due to small singlet-triplet splitting (Δ ). The strong orbital-coupling transitions of -(4-(1-(1-(2,3-dihydrobenzo[][1,4]dioxin-6-yl)-4,5-diphenyl-1-imidazol-2-yl)naphthalen-4-yl)phenyl)--phenyl benzenamine (DDPB) exhibit deep blue emission at 435 nm (CIEy, 0.07) with an external quantum efficiency of 2.01%. The electroluminescent efficiencies of 2-(1-(9-carbazol-9-yl)naphthalen-4-yl)-1-(2,3-dihydrobenzo[][1,4]dioxin-6-yl)-1-phenanthro[9,10-]imidazole (CDDPI) ( - 3992 cd m; - 3.01%; - 2.56 cd A; - 2.12 lm W) are higher than those of the -(4-(1-(1-(2,3-dihydrobenzo[][1,4]dioxin-6-yl)--phenanthro[9,10-]imidazole-2-yl)naphthalen-4-yl)phenyl)--phenylbenzenamine (DBDPA) based device ( - 3015 cd m; - 2.85%; - 2.01 cd A; - 1.92 lm W). The blue emissive materials CDDPI and DBDPA are used as a host to construct green and red phosphorescent OLEDs: the green device based on CDDPI:Ir(ppy) exhibits higher efficiencies ( - 8812 cd m; - 19.0%; - 27.5 cd A; - 33.0 lm W) at 2.7 V and the red device based on CDDPI:Ir(MQ)(acac) exhibits a maximum luminance of 39 661 cd m with excellent EL efficiencies [ - 19.2%; - 27.9 cd A; - 29.2 lm W; CIE (0.64, 0.34)] compared with those of the DBDPA:Ir(MQ)(acac) based device [ - 37 621 cd m; - 18.5%; - 25.2 cd A; - 25.8 lm W; CIE (0.64, 0.34)].