Alternating Phenylenevinylene Copolymers with Dithienbenzothiadiazole Moieties: Synthesis, Photophysical, and Photovoltaic Properties

Two new soluble alternating phenylenevinylene copolymers S and L which contained dithienbenzothiadiazole moieties were synthesized by Heck coupling. The repeating unit of L was longer than that of S and contained two additional phenylene rings and two cyano-vinylene bonds. Both copolymers were stable up to about 350 degrees C and afforded char yield of 52-66% at 800 degrees C in N-2. Their absorption spectra were broad and extended up to about 600 nm with a longer wavelength maximum at 447-502 nm and optical band gap of similar to 2.0 eV. These copolymers emitted yellow light in solution with PL maximum at 551-580 run and orange-red light in thin film with PL maximum at 588-661 nm. The emission maximum of L was considerably red-shifted relative to S. Photovoltaic cells based on S (or L) as donor and [6,6]-phenyl C61-butyric acid methyl ester as acceptor were investigated. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 2740-2750, 2009