Efficient, long-life and Lambertian source of top-emitting white OLEDs using low-reflectivity molybdenum anode and co-doping technology

A top-emitting white organic electroluminescent device (TWOLED) established on low-reflectivity molybdenum (Mo) anode (R similar to 58% in visible range) for alleviating the undesirable microcavity effect and achieving broad as well as similar emission spectra at different viewing angles has been demonstrated based on a dual-layer emitter composed of doped blue and yellow dopant in the same blue host. The electroluminescent (EL) efficiency and operational lifetime of TWOLED can be further enhanced by a factor of 1.2 and 3.4, respectively, when a co-doping technology of adding another blue dopant into the yellow emitter was incorporated. The enhanced efficiency is attributed to the improved energy transfer from blue host to yellow dopant by cascade process. (C) 2007 Elsevier B.V. All rights reserved.