Synthesis of new and fine organic electroluminescent materials and characterization study for light-emitting diodes (LEDs)

Abstract

Star-shaped organic light-emitting materials, CrossTPA and CrossCar, were prepared from palladium-catalyzed vinylation of organic halides. The synthesized materials were characterized by $^1H-NMR$, UV-visible spectroscopy, and etc. The maximum pho-toluminescence (PL) peaks of CrossTPA and CrossCar were found at 510 nm and 500 nm, respectively. The maximum electroluminescence (EL) peaks of CrossTPA and CrossCar were found at 520 nm and 500 nm, which were similar to the PL spectra. Turn-on voltages of CrossTPA and CrossCar were 13.5 V and 19 V when Al/emissive layer/ITO LED structure was fabricated. The fluorene based materials, FluTPA and Flu-Car, were prepared through palladium-catalyzed vinylation of organic halides. The maximum PL peaks of FluTPA and FluCar were found at 500 nm and 495 nm. Poly(di-n-hexylfluorene-2,7-diyl) (PDHF) and random copolymers resulting from the statistical incorporation of 1-[2-(2,5-dibromo-4-{2-[4-(2-ethylhexyloxy)phenyl]vinyl}phenyl)vi-nyl]-4-(2-ethylhexyloxy)benzene (DEP) end-capped with 9-bromoanthracene were synthesized through Ni(0)-mediated polymerization. To suppress excimer formation, comonomer is incorporated into the polymer main chain. The resulting polymers were soluble in common organic solvents. The ratios of the copolymer were varied. A single layer light-emitting diode device was fabricated which has a simple ITO (indium-tin oxide)/polymer/Al configuration. The PFCross13 showed the most luminescence under the same current.