US Patent 7847479 Organic electroluminescence element

An organic electroluminescence element including an organic layer including a light-emitting layer between a pair of electrodes, wherein the light-emitting layer contains at least two light-emitting materials having different Ea values and at least one host material, a concentration of a light-emitting material having a larger Ea value in the light-emitting layer gradually decreases from a cathode side toward an anode side, and a concentration of a light-emitting material having a smaller Ea value in the light-emitting layer gradually decreases from the anode side toward the cathode side.