Proceedings Article | 27 February 2002
KEYWORDS: Electroluminescence, Telescopic pixel displays, Electron transport, Thin films, Quantum efficiency, Glasses, Organic light emitting diodes, Luminescence, External quantum efficiency, Oxidation
A novel class of amorphous molecular materials, 1,3,5- tris(4-biphenylyl)benzene (TBB), 1.3.5-tris(4- fluorobiphenyl-4'-yl)benzene(F-TBB), 1,3,5-tris(9,9- dimethylfluoren-2-yl)benzene(TFB), and 1,3,5-tris[4-(9,9- dimethylfluoren-2-yl)phenyl]benzene(TFPB), were found to function as hole-blocking materials in organic electroluminescent (EL) devices. 1.3.5-Tris[5- (dimesitylboryl)thiophen-2-yl]benzene(TMB-TB) was also found to function as an electron transporter with better hole- blocking properties relative to tris(8- quinolinolato)aluminum. These materials, which readily form stable amorphous glasses with well-defined glass-transition temperatures, are characterized by relatively high oxidation potentials and large HOMO-LUMO energy gaps. The use of these materials as hole blockers in multilayer organic EL devices permitted efficient blue-violet emission from emitters with hole transporting properties, e.g., N,N'bis(e- methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (TPD), N,N'-bis(4-biphenylyl)-N,N'-diphenyl-[1,1'-biphenyl]- 4,4'-diamine(p-BPD), N,N-bis(9,9-dimethylfluorene-2- yl)aniline (F2PA), N,N'-bis[9,9-dimethylfluoren-2-yl]- N,N'-diphenyl-9,9-dimethylfluorene-2,7-diamine (PFFA), and N,N,N',N'-tetrakis(9,9-dimethylfluoren-2-yl)-[1,1'- biphenyl]-4,4'-diamine(FFD).
