Phosphorescent oled having double exciton-blocking layers

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;
• R1 through R8 are independently hydrogen, alkyl, phenyl or substituted phenyl, aryl amine, carbazole, or substituted carbazole and provided that R1-R8 do not contain aromatic hydrocarbon fused rings.