A blue organic light-emitting diode employing perylene as light emitting dopant and 9,10-bis(3’5’-diaryl)phenyl anthracene (DPA) as host has been studied for its decay mechanisms. The device structure is ITO(indium tin oxide)∕CuPc(copper phthalocyanine)∕NPD(α-naphthylphenylbiphenyl diamine)∕DPA:perylene∕Alq3 (8-hydroxy-quinoline aluminum)∕MgAg. In this device, CuPc and NPD are used as hole injection and transporting layers, DPA as a blue host, perylene as a blue emitting dopant, Alq3 as an electron transport layer, MgAg as cathode, respectively. A luminance of 4359cd∕m2 at 15V and a current efficiency of 3cd∕A at 5V have been achieved. The breakdown of the interfaces in the device is found to be one of the factors for the decay and the decomposition of the light emitter is not significantly studied by current–voltage–luminance, photoluminescence, and electroluminescence measurements. The lifetime is not intrinsic for this type of device.