Patent ID: 8866377

Claim:
An organic light emitting device, comprising: an anode; a cathode; an emissive layer disposed between the anode and the cathode, the emissive layer further comprising: a first organic layer comprising a first phosphorescent material and a first nonemissive material, wherein the concentration of the first phosphorescent material in the first organic layer is 10-90 wt %; and the concentration of the first non-emissive material in the first organic layer is 10-90 wt %; a second organic layer comprising a second phosphorescent material and a second non-emissive material, wherein the concentration of the second phosphorescent material in the second layer is 3-25 wt %; and the concentration of the second non-emissive material in the second organic layer is 75-97 wt %; wherein the concentration of the second phosphorescent material in the second organic layer is lower than the concentration of the first phosphorescent material in the first organic layer; wherein the first non-emissive material and the second non-emissive material may be the same material or different materials, and the first phosphorescent material and the second phosphorescent material may be the same material or different materials; wherein all organic layers between the first organic layer and the anode do not include any materials containing a group selected from the group consisting of triarylamine, napthyl, tri(N-carbazoyl)triphenylamine, tetraarylamine and carbazole; a third organic layer disposed between the first organic layer and the anode; and wherein the first phosphorescent material and the second phosphorescent material are the same material, and the first non-emissive material and the second non-emissive material are the same material.