Dithienopyrrole-based Donor-acceptor Copolymers: Low Band-gap Materials for Transport and Photovoltaics

摘要

Here, we report on the synthesis and characterization of a series of donor-acceptor conjugated copolymers based on dithieno[3,2-b:2',3'- d]pyrrole donors linked through thienylene bridges to benzothiadiazole- based acceptors. Both quantum-chemical calculations, and the optical and electrochemical properties of these copolymers suggest that the energy of the HOMO is only weakly dependent upon the choice of the acceptors, while the energy of the LUMO and the energy of the low- energy absorption band is strongly influenced by the acceptor. Both theory and experimental data indicate that the acceptor strength increases in the order benzothiadiazole < thiadiazolo[3,4-g]quinoxaline < benzobisthiadiazole. The low-energy absorption bands have considerable donor-to-acceptor charge-transfer character and, in the case of the compound with a benzobisthiadiazole acceptor, this band is found at ca. 1.2 μm. To our knowledge, this material is the lowest band-gap solution-processible polymer.