US Patent 8476823 Organic electroluminescent device

An organic electroluminescence device including at least an anode, an emitting layer, an electron-transporting region and a cathode in sequential order, wherein the emitting layer contains a host and a dopant which gives fluorescent emission of which the main peak wavelength is 550 nm or less; the affinity Ad of the dopant is equal to or larger than the affinity Ah of the host; the triplet energy ETd of the dopant is larger than the triplet energy ETh of the host; and a blocking layer is provided within the electron-transporting region such that it is adjacent to the emitting layer, and the triplet energy ETb of the blocking layer is larger than ETh.