Abstract
Optical, electrochemical and photovoltaic properties of novel donor-acceptor copolymers containing dithienylthienothiadiazole derivatives and 9,9-bis(2-ethylhexyl)fluorene or 2,5-diisopentoxybenzene units were studied. The copolymers exhibited long-wavelength absorption, and possess small optical bandgap in the range of 1.1 - 1.4 eV depending on copolymer units and alkyl side-chain nature and length. They exhibited ambipolar redox properties and electrochromism. Photovoltaic devices with bulk heterojunction made of blends of copolymers and fullerene derivatives were prepared. Effects of side-chain nature and length on photophysical properties are discussed.