Two kinds of blue OLEDs with the structure ITO/CuPc/NPB/JBEM:perylene/Alq/Mg:Ag [Device(J)] and ITO/CuPc/NPB/DPVBi:perylene/Alq/Mg:Ag[Device(D)]

were studied.The maximum luminance were 7526cd/m

2

and 6123cd/m

2

maximum luminous efficiency were 1.45lm/W and 0.831m/W for Device(J) and Device(D)

respectively. The difference of luminance and efficiency was not obvious for the two devices. However

there was remarkable difference for their lifetime. The Device(J) achieved the longer halflife of 1035h at initial luminance of 100cd/m

2

and that of Device(D) was only 255h. According to their energy level diagrams

the difference of stability may originate from light emitting materials in the two devices. It may be attributed to the higher thermal stability of JBEM molecules than that of DPVBi. JBEM may be a promising blue organic light emitting materials.