Novel copolymers consisting of the alternating push-pull comonomers fluorene and thieno[3,4-b]pyrazine/quinoxaline were synthesized by a palladium-catalyzed Suzuki cross-coupling reaction in 60-80% yields. The structure of the deeply colored copolymers was confirmed with H-1 and C-13 NMR. All the new materials were characterized with spectroscopic and electrochemical methods. Bulk heterojunction organic solar cells based on some of the novel polymers in combination with the well-known fullerene acceptor [6,6]phenyl C-61-butyric acid methyl ester were fabricated, and their photovoltaic parameters were measured. (c) 2006 Wiley Periodicals, Inc.