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

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,C 2 )iridium(III) picolinate (FIrpic). The host polymers, soluble polynorbornenes with pendant carbazole derivatives, N ‐phenyl‐9 H ‐carbazole ( P1 ), N ‐biphenyl‐9 H ‐carbazole ( P2 ), and 9,9′‐(1,3‐phenylene)bis‐9 H ‐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 ( T d5 > 410 °C) and glass transition temperatures ( T g ≈ 268 °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 2.7–3.0 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 (7–13 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.