Patent ID: 8034465

Claim:
An organic light-emitting device comprising: a. an anode; b. a cathode; c. a hole-transporting layer disposed between the anode and the cathode; d. a phosphorescent light-emitting layer disposed between the hole-transporting layer and the cathode, wherein the phosphorescent light-emitting layer includes at least one host and at least one phosphorescent dopant; e. a first exciton-blocking layer disposed between the hole-transporting layer and the phosphorescent light-emitting layer; wherein the first exciton-blocking layer includes a first exciton-blocking material that has a triplet energy greater than the triplet energy of the host in the phosphorescent light-emitting layer; and f. a second exciton-blocking layer disposed between the first exciton-blocking layer and the phosphorescent light-emitting layer, wherein the second exciton-blocking layer is in contact with the phosphorescent light-emitting layer, and wherein the second exciton-blocking layer includes a second exciton-blocking material that has a triplet energy less than the triplet energy of the first exciton-blocking material, wherein the first exciton-blocking material and the second exciton-blocking material are different carbazole derivatives represented by formula (J): wherein: n is an integer from 1 to 4; Q is phenyl, substituted phenyl, biphenyl, substituted biphenyl, aryl, or substituted aryl group; R 1 through R 8 are independently hydrogen, alkyl, phenyl or substituted phenyl, aryl amine, carbazole, or substituted carbazole and provided that R 1 -R 8 do not contain aromatic hydrocarbon fused rings.