White organic light emitting device

A white organic light emitting device comprising:

• an anode and a cathode opposing each other on a substrate;
• a charge generation layer interposed 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 blocking layer directly contacting the first hole transport layer, a first light emitting layer for emitting blue fluorescent light such that the first light emitting layer directly contacts the first blocking layer and comprises a first host and a fluorescent dopant in the first host, and a first electron transport layer directly contacting the first light emitting 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 blocking layer directly contacting the second hole transport layer, a second light emitting layer directly contacting the second blocking layer and comprising a second host and at least one phosphorescent dopant doped in the second host, and a second electron transport layer directly contacting the second light emitting layer,
• wherein the first light emitting layer and the second light emitting layer are single emitting layers in the first and second stack, respectively,
• wherein a triplet energy level of the first blocking layer is 0.01 eV to 0.4 eV higher than a triplet energy level of the first host to prevent diffusion of excitons from the first light emitting layer,
• wherein a triplet energy level of the first hole transport layer is less than the triplet energy level of the first blocking layer and greater than the triplet energy level of the first host, and
• wherein a hole mobility of the first hole transport layer is 5.0×10−4 cm2/s·V to 9.9×10−3 cm2/s·V.