Short-time synthesis of poly[4,6-bis(3′-(2-ethylhexyl)thien-2′-yl)thieno[3,4-c][1,2,5]thiadiazole-alt-9,9-dioctylfluorene], its photophysical, electrochemical and photovoltaic properties

Abstract

Short-time synthesis of new low-bandgap copolymer, CEHTF8, consisting of 4,6-bis(3′-(2-ethylhexyl)thien-2′-yl)thieno[3,4-c][1,2,5]thiadiazole and 9,9-dioctylfluorene by Suzuki coupling reaction in high-boiling solvents, such as chlorobenzene, dichlorobenzene and xylene is reported. Such synthesis yields high molecular copolymers in short reaction times of about 30 min; compared with these, several days are required using tetrahydrofuran (THF). It is proved that chlorinated solvents do not interfere with the reaction procedure and the final copolymers have the same structure and quality as those prepared in xylene or THF. High-molecular CEHTF8 copolymers of various molecular weights (MW) up to weight-average of MW 220 000 with low polydispersity index PDI 1.4–1.5 are synthesized. Their photophysical and electrochemical properties are reported. Photovoltaic devices with bulk heterojunction made of blends of copolymers possessing various MW and fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester ([60]PCBM) are prepared and characterized.