Highly efficient polymer phosphorescent light emitting devices

We fabricated two kinds of phosphorescent polymer light emitting devices us ing two different phosphorescent emitters doped in a host polymer poly (vin ylcarbazole) (PVK). Octaethylporphine platinum(II) (PtOEP) and tris(2-pheny lpyridine) iridium [Ir(ppy)(3)] were used as the guest emitters in the devi ces, respectively. The doping concentrations of the PtOEP and [Ir(ppy)(3)] were 6 and 8%, respectively. The emission spectra of the devices exhibited no emission from PVK, indicating that the energy transfer from PVK to guest molecules is efficient. The maximum quantum efficiency was 0.6 and 1.9% at low current for PtOEP and [lr(ppy)(3)] doped devices, respectively. The ef ficiency decreased as the current increased for both devices. However, the decreasing rate was slower for the [Ir(ppy)(3)] doped device, which may res ult from the shorter triplet exciton life time of [Ir(ppy)(3)] than that of PtOEP. The devices showed maximum brightness of 240 and 2500 cd m(-2) for the PtOEP and [Ir(ppy)(3)] doped devices, respectively. (C) 2001 Elsevier S cience B.V. All rights reserved.