1,3,5- tris[4'-(1 ''-phenylbenzimidazol-200-yl)phenyl]benzene (BTPBB), was synthesized and its electroluminescence (EL) properties were investigated. In order to enhance the emission efficiency, the device structure was optimized by balancing the charge carrier injection and reducing the barrier height for electron transport to the emitting layer. The OLED device with a structure of [ITO/alpha-NPB (50 nm)/BTPBB (30 nm)/TPBI (10 nm)/Alq3 (20 nm)/LiF (1 nm)/Al (120 nm)] exhibited the luminous efficiency of 2.2 cd/A and the external quantum efficiency of 0.9% at 120mA/cm(2) with the CIE 1931 color coordinates of (0.15, 0.08), which was pure blue and almost invariant within the operating voltage range of 12 similar to 19.5 V.