Patent ID: 8829504

Claim:
A white organic light emitting device comprising: an anode and a cathode opposing each other on a substrate; a charge generation layer between the anode and the cathode; a first stack interposed between the anode and the charge generation layer, the first stack including a first hole transport layer, a first light emitting layer emitting blue light and a first electron transport layer; and a second stack interposed between the charge generation layer and the cathode, the second stack including a second hole transport layer, a second light emitting layer formed by doping one host with a phosphorescent dopant, and a second electron transport layer, wherein at least one of the first hole transport layer and the second hole transport layer has a triplet energy level higher than a triplet energy level of the light emitting layer adjacent thereto, and a difference (ΔEst) between a triplet energy level and a singlet energy level of 0.35 eV to 0.6 eV, wherein the first hole transport layer has a triplet energy level that is 0.01 eV to 0.4 eV higher than a triplet energy level of the first light emitting layer and, wherein the triplet energy level of the first hole transport layer is 2.6 eV to 2.73 eV and wherein the band gap energy of the first hole transport layer is 3.0 eV to 3.4 eV.