Soluble polynorbornenes with pendant carbazole derivatives as host materials for highly efficient blue phosphorescent organic light-emitting diodes

Abstract

We report novel host polymers for a high-efficiency polymer-based solution-processed phosphorescent organic light-emitting diode with typical blue-emitting dopant bis(4,6-difluorophenylpyridinato-N,C2)iridium(III) picolinate (FIrpic). The host polymers, soluble polynorbornenes with pendant carbazole derivatives, N-phenyl-9H-carbazole (P1), N-biphenyl-9H-carbazole (P2), and 9,9'-(1,3-phenylene)bis-9H-carbazole (mCP) (P3) are efficiently synthesized by vinyl addition polymerization of norbornene monomers using Pd(II) catalyst in combination with 1-octene chain transfer agent. The polymers exhibit high thermal stability with high decomposition (Td5 > 410 degrees C) and glass transition temperatures (T-g approximate to 268 degrees C). The HOMO (ca. -5.5 to -5.7 eV) and LUMO (ca. -2.0 to -2.1 eV) levels with the high triplet energy of about 2.73.0 eV suggest that the polymers are suitable for a host material for blue emitters. Among the solution-processed devices that were fabricated based on the emissive layers containing the P1-P3 host doped with various concentrations of FIrpic (713 wt %), the best device with P3 host exhibits power efficiency of 3.0 lm W-1 and external quantum efficiency of 4.0% at a luminance of 1000 cd m-2 that is outstanding among the polymeric rivals. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012