Devices using red phosphorescent dye as dopant with exciton blocking layer were constructed. The device structure is ITO/CuPc/NPB/TPBi:Btp2Ir(acac)/TPBi/Alq/LiF/Al. The EL spectra, luminance-current, efficiency-current characteristics of the device have been investigated. At the CIE coordinates x=0.62，y=0.35，efficiency 2.43cd /A has been achieved. At 20mA/cm2 and 400mA/cm2, luminance is 431cd/m2 and 4798 cd/m2, respectively. The effects of the emitting layer thickness on efficiency and EL spectra of the device have been studied also. With the decrease of the emitting layer thickness, efficiency decreases and the blue band of the El spectra increases. For the thickness d2Ir(acac) HOMO energy level. For the thickness d>20nm, the decrease of the efficiency is attributed to the added invalid emitting-layer and more annihilation centers.