Phosphorescence of red Os(fptz) 2(PPh 2Me) 2 doped organic light-emitting devices with n and p hosts

Abstract

We have applied a stericly-hindered red phosphorescent dopant Os (fptz)2 (P Ph2 Me)2 [fptz=3 -trifluoromethyl-5-(2-pyridyl)-1,2,4-triazole, P Ph2 Me=phosphine ligand] in p -type 4, 4′ - N, N′ -dicarbazole-biphenyl or n -type bis(2-methyl-8-quinolinolato) (p -phenylphenolato) aluminum host and found that the latter produced higher luminance efficiency at lower doping concentration. We present a model to rationalize this phenomenon in which the n -type host impedes hole transport, which leads to narrower recombination zone near the hole transport layer/emission layer interface than the p -type host, hence, more effective recombination. © 2006 American Institute of Physics.