Alcohol-soluble heteroalkylthiophene derivatives: inside the role of cathode interlayers for green energy production

The inorganic photovoltaic technology currently available on the market presents high production, purchase and installation costs, thus leading the research to focus on the development of alternative semiconductor materials, such as π-conjugated polymers. However, although the advantages of these polymers are several, they are often soluble in toxic and harmful solvents with a high environmental impact. Consequently, the development of water/alcohol-soluble conjugated polymers (WSCPs) has become the subject of extensive study, as they combine excellent optical properties with solubility in “green” solvents. This work is therefore focused on the synthesis of two different class of thiophene-based copolymers, both containing different content of oxygen directly connected to the ring. Specifically, dye-sensitized (P1a-TPP and P2a-TPP) and push-pull (P1b-Bz and P2b-Bz) copolymers were synthesized by oxidative coupling with iron trichloride and Suzuki cross-coupling reaction, respectively. Then, by post-functionalization approach with tributyl phosphine, ionic alcohol-soluble polymers were prepared. All these materials were thoroughly characterized by means of spectroscopic techniques and subsequently tested as cathode interlayers, in halogen-free photovoltaic organic solar cells of BHJ configuration.