Synthesis, photophysical and optoelectronic properties of quinazoline-centered dyes and their applications in organic light-emitting diodes

Quinazoline-centered derivatives with benzoimidazole, carbazole, and triphenylene moieties, were synthesized. Their relationships between electrochemical, photophysical, and optoelectronic properties and structure were discussed in detail. Efficient red phosphorescent organic light-emitting diodes with low turn-on voltage were demonstrated by using them as host materials, and achieved maximum external quantum efficiencies, current efficiencies, and power efficiencies of 19.2%, 18.3 cd/A, 21.7 lm/W for 4-[4-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl]-2-[3-(tri-phenylen-2-yl)phen-3-yl]quinazoline, of 18.4%, 17.6 cd/A, 19.3 lm/W for 4-(9-phenyl-9H-carbazol-3-yl)-2-[3-(triphenylen-2-yl)phenyl]quinazoline, of 15.6%, 14.4 cd/A, 16.7 lm/W for 2,4-bis[4-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl]quinazoline, and of 17.4%, 16.7 cd/A, 15.7 lm/W for 2,4-bis(9-phenyl-9H-carbazol-3-yl)quinazoline, respectively. Moreover, improving the electron-injection/transport abilities of host materials could ideally improve the performance of organic light-emitting diodes under low operation voltage, while enhancement of hole-transporting abilities by using bipolar materials could balance the carriers to maintain high efficiency under high operating voltage. These materials exhibited high glass-transition temperature of 146–154 °C and decomposition temperature of 400–447 °C.