Highly efficient polymer phosphorescent light emitting devices

Abstract

We fabricated two kinds of phosphorescent polymer light emitting devices using two different phosphorescent emitters doped in a host polymer poly (vinylcarbazole) (PVK). Octaethylporphine platinum(II) (PtOEP) and tris(2-phenylpyridine) iridium [Ir(ppy)(3)] were used as the guest emitters in the devices, 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 efficiency decreased as the current increased for both devices. However, the decreasing rate was slower for the [Ir(ppy)(3)] doped device, which may result 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 Science B.V. All rights reserved.