(Bi)phenyl substituted 9-(2,2-diphenylvinyl)carbazoles as low cost hole transporting materials for efficient red PhOLEDs

Two low-cost 9-(2,2-diphenylvinyl)carbazole-based derivatives with aryl substitutions were synthesized by simple procedure and then investigated. The respective glass transition temperatures of the materials were estimated to be higher than 90 °C, which can provide morphologically-stable amorphous films for applications in organic light emitting diodes. The compounds possess adequate ionization potentials and suitable triplet energies, which make them suitable hole transporting materials for use in red phosphorescent organic light-emitting diodes. The respective peak efficiencies of the red devices with the p-type dopants were recorded at 8.7% (5.6 cd/A and 3.9 lm/W) and at 8.7% (5.4 cd/A and 3.8 lm/W), correspondingly, demonstrating high potential of the material for applications in light emitting diodes. The characteristics indicated that the devices with the aryl substituted 9-(2,2-diphenylvinyl)carbazoles exhibit better performance than those of widely used hole transporting 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) -based device.