2-diphenylaminofluoren-7-ylstyrene derivatives with various aromatic end-capping groups for highly efficient blue and white organic light-emitting diodes

Highly efficient blue fluorescent materials with a 2-diphenylaminofluoren- 7-ylstyrene emitting unit and various aromatic end-capping groups were synthesized and characterized. A 2-methyl-9,10-bis(2-naphthyl)anthracene host was doped with these blue materials as the blue dopants in the emitting layer of organic light-emitting diode (OLED) devices. All devices exhibited highly efficient blue electroluminescence with high external quantum efficiency (4.38-6.2 % at 20 mA cm^-2). In particular, two deep blue OLEDs using 7-[3,5-bis(naphthalen-1-yl)styryl]-9,9-diethyl-2-N,N-diphenylamino-9H-fluorene (1f) and 7-{4-[1′-(2′,3′,4′,5′-tetraphenyl)phenyl] styryl}-9,9-diethyl-2-N,N-diphenylamino-9H-fluorene (1g) as dopants in the emitting layer showed high external quantum efficiencies of 4.63 and 5.96 % at 20 mA cm^-2 with the color coordinates (0.148, 0.134) and (0.147, 0.144), respectively. A sky-blue OLED using7-{4-[9,9′-spirobi(fluoren)-2- yl]styryl}-9,9-diethyl-2-N,N-diphenylamino-9H-fluorene (1e) exhibited a high quantum efficiency of 6.20 % at 20 mA cm^-2 with the color coordinates (0.148, 0.195). Moreover, efficient white OLEDs with an external quantum efficiency, luminous efficiency, and color coordinates of 6.50 %, 10.3 cd A ^-1 at 20 mA cm^-2 and (0.357, 0.310) at 1000 cd m ^-2 were demonstrated by exploiting this highly efficient blue fluorescent material (1e) as a dopant in the blue-emitting layer.