Highly efficient green and red phosphorescent OLEDs using novel bipolar blue fluorescent materials as hosts

We investigated highly efficient green and red phosphorescent organic light-emitting diodes (OLEDs) based on two kinds of iridium complexes as the guests and two novel 1,3,5-triazine derivatives as the host materials, respectively. For comparison, the devices using a common fluorescent host 4,4'-N,N'-dicarbazolebiphenyl (CBP) have also been fabricated. Results show that all devices using 1,3,5-triazine derivatives as host have better performance than that of CBP. This may be attributed to the adoption of the hosts, which have suitable HOMO/LUMO levels enabling excitons to form on host and hence favoring efficient energy-transfer from host to guest. In addition, the high bipolar carrier mobility of the host is found to be critical to this kind of doping system, which would balance the injection of both carriers and improve efficiency. (C) 2014 Elsevier B.V. All rights reserved.