Multi-triphenylamine-substituted carbazoles: synthesis, characterization, properties, and applications as hole-transporting materials

A series of triphenylamine-substituted carbazoles, namely TnC (n = 2-4), are synthesized and characterized. By increasing the number of triphenylamine substituents, we are able to reduce the crystallization and improve the thermal stability of the molecule. Their thermal properties and abilities as hole-transporting layers in Alq3-based OLED, especially T4C having four triphenylamine substituents, are greater than both the common hole-transporters, N,N′-diphenyl-N,N′-bis(1-naphthyl)-(1,1′-biphenyl)-4,4′-diamine (NPB) and N,N′-bis(3-methylphenyl)-N,N′-bis(phenyl)benzidine (TPD). A green light-emitting device with a luminance efficiency as high as 5.07 cd/A is achieved.