Blue electroluminescent materials based on 2,7-distyrylfluorene for organic light-emitting diodes

摘要

A series of blue fluorescent 9,9-diethyl-2,7-distyryl-9H-fluorene derivatives with various capping moieties such as diphenylamino; diphenylphosphino; triphenylsilyl; phenoxy; phenylmercapto; phenylselenoxy; and triphenymethyl groups were synthesized using the Honor-Emmons reaction. The highest occupied molecular orbital-lowest unoccupied molecular orbital energy levels were characterized with a photoelec-tron spectrometer and rationalized with quantum mechanical density functional theory calculations. The electroluminescent properties were explored through the fabrication of multilayer devices with a structure of Indium-tin-oxide/N,N'-diphenyl-N,N'-(1-napthyl)-(1,1'-phenyl)-4,4'-diamine/2-methyl-9,10-di(2-naphthyl)anthracene:blue dopants (5-15 wt.%)/4,7-diphenyl-1,10-phenanthroline/lithium quinolate/Al. All devices, except that using NPh_2, exhibited a Commission Internationale de I'Eclairage (CIE) y value less than 0.19. The best luminous efficiency of 3.87 cd/A and external quantum efficiency of 2.65% at 20 mA/cm~2 were obtained in a device comprising the 4-phenylsulfanyl capped 9,9-diethyl-2,7-distyrylfluorene derivative with CIE coordinates (0.16, 0.18).