Abstract
Novel copolymer derived from ethoxylated fluorene and 4,7-dithienyl-2,1,3-benzothiadiazole was successfully synthesized by palladium(0)-catalyzed Suziki coupling reactions. Optoelectronic properties of the copolymer were characterized by elemental analysis, NMR, UV absorption, photoluminescence (PL), and electroluminescence (EL). The films of the copolymer showed DBT-dominant red emissions. EL devices of the copolymer with a sandwich configuration of ITO/Polymer/Al displayed exclusive DBT emissions peaked at around 655 nm with the CIE coordinate of (0.67, 0.32). The polymer layer contained a conjugated copolymer that emits red light, trimethylolpropane trimethacrylate (TMPTMA), a low vapor pressure highly crosslinkable liquid, and lithium trifluoromethane sulfonate (LiTf) at a weight ratio of 20:40:1. A dynamic p-i-n junction was formed in thin films of light emitting polymers admixed with an ionically conductive medium. The PLEC device was turned on at relative low voltage 3.2 V and the brightness reached up to 1200 cd/m2 at 8 V.