New Fluorene Derivatives for Blue Electroluminescent Devices: Influence of Substituents on Thermal Properties, Photoluminescence, and Electroluminescence

Abstract

A new series of fluorene derivatives with different substituents at the C-2,7- and C-9 positions has been synthesized and characterized with respect to their luminescence and thermal properties. It was found that substitutions at the C-2,7 positions significantly affected the thermal properties and optical properties, whereas substitutions at the C-9 position mainly affected the thermal properties of the fluorene derivatives. Organic light-emitting diodes (OLEDs) with a structure of indium tin oxide (ITO)/copper phthalocyanine (CuPc) (15 nm)/4,4‘-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) (50 nm)/fluorene derivative (30 nm)/tris(8-quinolinolato)aluminum (Alq3) (50 nm)/Mg/Ag (200 nm) were fabricated. OLEDs based on the naphthyl-substituted fluorenes gave saturated blue emission centered at 452 nm, while those based on anthryl-substituted fluorenes showed a blue−green emission with a wider spectrum. OLEDs based on 2,7-dipyrenyl-9‘9-dimethylfluorene (DPF) exhibited blue emission with a maximum efficienc...