Electroluminescence Characteristics of a New Green-Emitting Phenothiazine Derivative with Biphenyl Benzimidazole Substituent

We report on the synthesis and electroluminescence characteristics of a new green-emitting material, 3,7-bis(1-(biphenyl-4-yl)benzimidazol-2-yl)10-methylphenothiazine (PhBBMP) containing the electron-donating phenothiazine core and the electron-accepting biphenyl benzimidazole substituent. An optimized OLED device with the structure of [ITO/NPB (40 nm)/PhBBMP (30 nm)/BCP (10 nm)/TPBI (30 nm)/LiF (1 nm)/Al (100 nm)] exhibited a luminous efficiency of 4.5 cd/A and an external quantum efficiency of 0.9% at 100 mA/cm2, and the maximum luminance of 12,000 cd/m2 with the CIE 1931 chromaticity coordinates of (0.21, 0.54). A more balanced charge carrier injection and the charge confinement in the emitting layer cooperatively contributed to improve the performance of the device prepared with the PhBBMP emitting layer.