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.