Thermally stable organic electroluminescent device using novel amorphous molecular charge-transport materials, 4,4',4''-tris[bis(4'-tert-butylbiphenyl-4-yl)amino]triphenylamine and 4,4',4''-tri(N-carbazolyl)triphenylamine

For the purpose of developing an amorphous molecular material with a high glass-transition temperature (Tg) and a low ionization potential for use as a charge-transport layer in organic electroluminescent (EL) devices, a novel starburst molecule, 4,4',4 ''-tris[bis(4'-tert-butylbiphenyl-4-yl)amino] triphenylamine (t-Bu-TBATA), was designed and synthesized. t-Bu-TBATA was found to form readily a stable glass with a Tg of 203 degrees C. A multilayer EL device consisting of double hole-transport layers of t-Bu-TBATA and 4,4',4 ''-tri(N-carbazolyl)triphenylamine and an emitting layer of tris(8-quinolinolato)aluminum was fabricated and its performances were examined. The device was found to exhibit good performances and to be thermally stable, operating even at 170 degrees C.