Color-stable white-light-emitting diodes doped with phosphorescent dopants via enhanced energy transfer through homogeneous morphology

We demonstrate that white light-emitting diodes using polyfluorene-based blue-emitting conjugated copolymer and small molecule as co-host doped with green and red-emitting phosphorescent dyes. The energy transfer from co-host to phosphorescent dyes is enhanced by blending with small molecule due to the suppressed phase separation between conjugated polymer and Ir complexes as well as the high triplet state of co-host. We obtained voltage-independent pure white light emission with homogeneous morphology in the blended single active layer system by reducing charge trapping in Ir complexes and enhancing the efficient Förster energy transfer.