An organic light-emitting device comprising: a) an anode; b) a cathode; c) a phosphorescent light-emitting layer disposed between the anode and the cathode, wherein the phosphorescent light-emitting layer includes at least one host and at least one phosphorescent dopant; d) a first hole-blocking layer disposed in contact with the phosphorescent light-emitting layer at the cathode side, wherein the first hole-blocking layer includes a first hole-blocking material having a triplet energy greater than the triplet energy of the predominant host in the phosphorescent light-emitting layer; and wherein the HOMO energy of the first hole-blocking material in the first hole-blocking layer is lower than that of the predominant host in the phosphorescent light-emitting layer; e) a second hole-blocking layer disposed in contact with the first hole-blocking layer at the cathode side, wherein the second hole-blocking layer includes a second hole-blocking material having a triplet energy greater than the triplet energy of the dopant in the phosphorescent light-emitting layer, and wherein the HOMO energy of the second hole-blocking material in the second hole-blocking layer is lower than that of the predominant host in the phosphorescent light-emitting layer; and f) an electron-transporting layer disposed between the second hole-blocking layer and the cathode, wherein the electron-transporting layer includes at least one electron-transporting material; wherein there is a LUMO energy difference between the predominant host in the phosphorescent light-emitting layer and the first hole-blocking material in the first hole-blocking layer, and wherein the LUMO energy difference is less than 0.5 V; and wherein the first hole-blocking material in the first hole-blocking layer and the second hole-blocking material in the second hole-blocking layer are different electron-transporting materials. a) an anode; b) a cathode; c) a phosphorescent light-emitting layer disposed between the anode and the cathode, wherein the phosphorescent light-emitting layer includes at least one host and at least one phosphorescent dopant; d) a first hole-blocking layer disposed in contact with the phosphorescent light-emitting layer at the cathode side, wherein the first hole-blocking layer includes a first hole-blocking material having a triplet energy greater than the triplet energy of the predominant host in the phosphorescent light-emitting layer; and wherein the HOMO energy of the first hole-blocking material in the first hole-blocking layer is lower than that of the predominant host in the phosphorescent light-emitting layer; e) a second hole-blocking layer disposed in contact with the first hole-blocking layer at the cathode side, wherein the second hole-blocking layer includes a second hole-blocking material having a triplet energy greater than the triplet energy of the dopant in the phosphorescent light-emitting layer, and wherein the HOMO energy of the second hole-blocking material in the second hole-blocking layer is lower than that of the predominant host in the phosphorescent light-emitting layer; and f) an electron-transporting layer disposed between the second hole-blocking layer and the cathode, wherein the electron-transporting layer includes at least one electron-transporting material;