Use of poly(9-vinylcarbazole) as host material for iridium complexes in high-efficiency organic light-emitting devices

Using poly(9-vinylcarbazole) (PVCz) as a host material for tris(2-phenylpyridine)iridium (Ir(ppy)(3)) guest emitter, double-layer and triple-layer organic light-emitting devices were fabricated. Tris(8-hydroxyquinolino)aluminum (Alq(3)) and 1,3-bis[(4-tert-butylphenyl)-1,3,4-oxadiazolyl]phenylene (OXD-7) were used for electron-transporting layers. The insertion of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) as a hole-blocking layer was also tested. The double-layer device composed of PVCz doped with 6.8 wt% Ir(ppy)(3) and OXD-7 gave the highest external quantum efficiency of 7.5% and power luminous efficiency of 5.8 lm/W at the luminance of 106 cd/m(2) (current density of 0.40 mA/cm(2) and drive voltage of 14.5 V).