New regioregular polythiophenes functionalized with sulfur-containing substituents for bulk heterojunction solar cells

Organic photovoltaic devices fabricated with polythiophenic derivatives and single-walled carbon nanotubes (SWCNT)s have been assembled and tested. For this purpose, some new regioregular polythiophenes with different sulfur-containing groups in the terminal position of a hexamethylenic side chain were prepared using direct and indirect polymerization routes. The optical features of the synthesized polymers were examined and compared by registering their UV-Vis spectra in different solvent/non-solvent systems and in film; their thermal stability, electrical conductivity, cyclic voltammetry and photovoltaic properties were carefully analyzed. In particular, the two samples bearing the sulfinyl group in side chain showed better chromic responses, enhanced self-assembling capabilities, more extended conjugation length, higher electrical conductivity and very promising photovoltaic performances, when compared to those of analogous systems reported on up to now.