A novel π-conjugated starburst molecule, 4,4′,4″-tris(3-methylphenylphenylamino)triphenylamine (m-MTDATA), which forms a stable amorphous glass, functions as an excellent hole transport material for organic electroluminescent devices. An electroluminescent device consisting of double hole transport layers of m-MTDATA and 4,4′-bis(3-methylphenylphenylamino)biphenyl and an emitting layer of tris(8-quinolinolato)aluminum exhibits a high luminance efficiency and significant durability.

Multilayer organic light-emitting devices with phosphorescent guest emitter, tris(2-phenylpyridine) iridium doped in a host 4,4′-N,N′-dicarbazol-biphenyl layer were prepared. The device with the 6.5 wt% guest emitter exhibited external quantum efficiency and power luminous efficiency of 13.7% and 38.3 lm/W, respectively at the luminance of 105 cd/m2 driven at the voltage of 4.0 V and current density of 0.215 mA/cm2. The half decay lifetime under continuous constant-current driving for the initial luminance of 500 cd/m2 was 170 h.

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