Blue aggregation-induced emission bipolar materials consisting of diphenylsulfone or benzophenone core and triphenylethene-carbazole fragments for highly efficient OLEDs

Bipolar derivatives having aggregation-induced emission (AIE) properties were synthesized in reactions of 4,4’-difluorobenzophenone, 4-fluorophenyl-phenylsulfone or bis(4-fluorophenyl)sulfone with prepared key starting materials: 1,1,2-triphenyl-2-(9H-carbazol-2-yl)ethylene or 1-(9H-carbazol-2-yl)-4-(1,2,2-triphenylethenyl)benzene. The objective materials have shown high thermal stabilities and can form amorphous layers having high glass transition temperatures in the region of 110 -173 oC. The photoluminescence spectra of the prepared derivatives registered using tetrahydrofuran-water solutions demonstrated strong blue emissions, confirming their AIE property. Thin films of the compounds were tested in multilayer organic light-emitting diodes. The device using bis(4-{2-[4-(1,1,2-triphenylethylenyl)phenyl]carbazol-9-yl}phenyl)sulfone emitter (EM3) outperformed the other devices, achieving a peak efficiencies of 3.4% (5.6 cd/A and 4.7 lm/W) with maximum luminance of about 11000 cd/m2. However OLED using 4-{2-[4-(1,1,2-triphenylethylenyl)phenyl]carbazol-9-yl}phenyl-phenylsulfone (EM2) as emitter demonstrated higher efficiency at higher luminance values. The maximum efficiencies of the device were obtained at a luminance value of about 100 cd/m2 and were recorded as 3.2% (5.2 cd/A and 4.1 lm/W) with luminance of 17515 cd/m2.