1-(N-phenylamino)naphthalene oligomers as novel hole transport materials for highly efficient green electrophosphorescence

摘要

Two hole transport materials, N-(4-carbazol-9-yl-phenyl)-N'-naphthalen-1-yl-N,N'-diphenyl-naphthalene-1,4-diamine and N-(4-carbazol-9-yl-phenyl)-N'-(4-N,N- phenyl-naphthalene-naphthalen-1-y1)-N,N'-diphenyl-naphthalene-1,4-diamine, were synthesized by the addition of a carbazole moiety on to the dimer or trimer of N-phenyl-1-naphthylamine. Both of these hole transport materials have high glass transition temperatures of 135 and 167 degrees C, respectively. The green phosphorescent organic light-emitting diodes (PHOLEDs) of ITO (indium tin oxide)ew hole transport material (50 nm)/Ir(tfmppy)2(tpip) (tfmppy = 4-trifluoromethylphenyl-pyridine, tpip = tetraphenylimidodiphosphinate, 8 wt%): mCP (N,N'-dicarbazoly1-3,5-benzene, 25 nm)/TmPyPB (1,3,5-trim-pyrid-3-yl-phenyl)benzene, 50 nm)/LiF(1 nm)/Al (100 nm) exhibit high efficiency (maximum current efficiency (eta(c,max)) of 113.9 and 108.8 cd A(-1), maximum external quantum efficiency (EQE) of 29.8% and 28.5%, respectively) with a low efficiency roll-off. At 3000 cd m(-2) brightness, the eta(c) values still remain as high as 1093 and 105.3 cd A(-1), respectively. The device performances proved that these new materials derived from N-phenyl-1-naphthylamine would be promising hole transport materials for PHOLEDs. (C) 2015 Elsevier Ltd. All rights reserved.