Synthesis and Characterization of a New Series of Blue Fluorescent 2,6-Linked 9,10-Diphenylanthrylenephenylene Copolymers and Their Application for Polymer Light-Emitting Diodes

A series of new 9,10-diphenylanthracene-based, 2,6-linked blue-light-emitting copolymers bearing hole- or electron-transporter as well as bulky substituent were successfully synthesized. Photo-physical, thermal, electrochemical, and electroluminescence (EL) properties of these copolymers were studied and characterized. Bright and efficient blue fluorescence in the solid state was achieved by incorporating bulky substituent into the copolymer backbone. Both hole- and electron-transport-substituted copolymers apparently enhanced the electroluminescent performance of their polymeric light-emitting diodes (PLEDs). A diphenylvinyl-bearing copolymer (pDPV) PLED exhibited sky-blue EL (lambda(EL)(max) = 473 nm, CIEx,y = 0.16, 0.28) with peak luminous efficiency of 2.21 cd/A; a N-carbazole bearing copolymer (pCBZ) PLED displayed a blue EL (lambda(EL)(max) = 469 nm, CIEx,y = 0.15, 0.22) with peak luminous efficiency of 2.15 cd/A. OXD-7 (1,3-bis(2-(4-tert-butylphenyl)-1,3,4-oxadiazol-5-yl)benzene) as an electron-transporting dopant was found to improve the performance of PLED significantly. A better balanced hole/electron charge carrier was ascribed to electron-transporting, 1,3,4-oxadiazole-bearing copolymer (pOXD) PLED. It showed a very mild efficiency rolls off: only 0.13 cd/A luminous efficiency drops from current densities of 10-100 mA/cm(2), corresponding to EL brightness of 169-1558 cd/m(2).