Patent ID: 8810125
Filing Date: 2014-08-19
Classification: H01L

Abstract:
1. A light emitting element comprising: an anode; a first layer over the anode; a second layer over the first layer; a third layer over the second layer; and a fourth layer over the third layer, wherein the first layer comprises a first substance having a light emitting property and a first host material, wherein the second layer comprises a second substance having a light emitting property and a second host material, wherein the third layer comprises a third substance having a light emitting property and a third host material, wherein the fourth layer comprises a fourth substance having a light emitting property and a fourth host material, wherein triplet excitation energy of the second host material is higher than or equal to triplet excitation energy of the first host material, wherein triplet excitation energy of the third host material is higher than or equal to triplet excitation energy of the fourth host material, wherein triplet-excitation energy generated in the second layer is transferred to the first layer to emit a light from triplet excited state of the first substance having the light emitting property, and wherein triplet-excitation energy generated in the third layer is transferred to the fourth layer to emit a light from triplet excited state of the fourth substance having the light emitting property.