Organic light-emitting devices based on phosphorescent hosts and dyes

Phosphorescent dyes may lead to more efficient electroluminescent devices, since triplets should be formed in a 3-fold excess compared to singlets. Ef ficient devices are presented here that have been constructed using phospho rescent dye-doped layers as both the electron transporting and emitting lay er. Triplet energy transfer from the host Ir(ppy)(3) to the red phosphoresc ent dopant PtOX (see Figure) was observed directly.