Materials and architectures for efficient harvesting of singlet and triplet excitons for white light emitting OLEDs

An organic light emitting device comprising:

• a cathode,
• an emissive region, and
• an anode
• wherein,
• the emissive region consists of:
• a fluorescent layer comprising a fluorescent emitting dopant, and a charge-transporting dopant in a host material,
• one or more phosphorescent layers, each comprising a phosphorescent emitting dopant, and a charge-transporting dopant in a host material, and
• an optional spacer layer between the fluorescent layer and a phosphorescent layer comprising a charge-transporting dopant in a host material,
• wherein the host material for the fluorescent layer, the host material for the phosphorescent layers and the host material for the spacer layer, if present, are the same material;
• and
• wherein the charge-transporting dopant is a hole-transporting dopant or the charge-transporting dopant is an electron-transporting dopant, wherein if the charge-transporting dopant is a hole-transporting dopant, the HOMO level of the hole-transporting dopant is above and closer to the vacuum energy level than the HOMO level of the fluorescent emitting dopant and the HOMO level of the phosphorescent emitting dopant or if the charge-transporting dopant is an electron-transporting dopant, the LUMO level of the electron-transporting dopant is below the LUMO level of the fluorescent emitting dopant and the LUMO level of the phosphorescent emitting dopant, and wherein the triplet energy of the charge-transporting dopant is higher than the triplet energy of the host material.