Luminescent properties of a novel naphthalimide-fluorene molecule

A novel naphthalimide-fluorene molecule, 4-(N,N-dimethylamino)-N-(2′-fluorenyl)-1,8-naphthalimide (DFN), has been synthesized and characterized, and its luminescent properties have been studied. DFN has an absorption maximum at 420 nm and possesses solvent polarity dependent changes. The environmental sensitivity exhibited the characteristics of an excited state charge transfer complex. DFN also showed strong luminescence, good electron-affinity, and temperature independence of fluorescence. The application of DFN in organic light-emitting diodes (OLEDs) as an electron-transporting electroluminescent material was investigated. The OLED with a structure of ITO/N,N′-bis(3-methylphenyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine/DFN/Al shows a yellow-green emission (chromaticity coordinates: x = 0.424, y = 0.543) with a brightness of 3563 cd/m2. The external quantum efficiency and the highest luminous efficiency of the device reach 0.2% and 0.55 lm/W, respectively.