Semiconducting Conjugated Copolymer Series for Organic Photonics and Electronics

Abstract

Donor–acceptor copolymer series containing 4,6-di (thien-2′-yl) thieno [3,4-c][1,2,5] thiadiazole or its derivatives serving as electron-acceptor units and various electron-donor units such as 9,9-bis (alkyl) fluorene, benzene, bithiophene or carbazole derivatives is reported. These copolymers possess narrow optical band gap in the range of 1.0 - 1.5 eV depending on the character of the donor units. They exhibit relatively high electron affinity. Absorption of copolymer thin films covers the whole visible spectral region extended up to NIR for some copolymers. The influence of side chain nature and molecular weight on their photophysical properties is shown. Selected copolymers are used in the blends with fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester ([60]PCBM) as active layers in bulk heterojunction photovoltaic devices. The results are discussed in relation to the copolymer structure, side chain nature and molecular weight.