Highly efficient blue OLEDs based on diphenylaminofluorenylstyrenes end-capped with heterocyclic aromatics

In this paper, we have designed four diphenylaminofluorenylstyrene derivatives end-capped with heterocyclic aromatic groups, such as 9-phenylcabazole, 4-dibenzofuran, 2-benzoxazole, 2-quinoxaline, respectively. These materials showed blue to red fluorescence with maximum emission wavelengths of 476–611nm, respectively, which were dependent on the structural and electronic nature of end-capping groups. To explore the electroluminescent properties of these materials, multilayer OLEDs were fabricated in the following sequence: ITO/DNTPD (40nm)/NPB (20nm)/2% doped in MADN (20nm)/Alq3 (40nm)/Liq. (1nm)/Al. Among those, a device exhibited a highly efficient blue emission with the maximum luminance of 14,480cd/m2 at 9V, the luminous efficiency of 5.38cd/A at 20mA/cm2, power efficiency of 2.77lm/W at 20mA/cm2, and CIEx,y coordinates of (0.147, 0.152) at 8V, respectively.