Side-chain Tunability of Furan-containing Low Band-Gap Polymers Provides Control of Structural Order in Efficient Solar Cells

摘要

The solution-processability of conjugated polymers in organic media has classically been achieved by modulating the size and branching of alkyl substituents appended to the backbone. However, these substituents impact structural order and charge transport properties in thin-film devices. As a result, a tradeoff must typically be found between material solubility and insulating alkyl content. Here, we report the design, synthesis, and characterization of the first example of a furan-containing low band-gap polymer, PDPP2FT, with substantial power conversion efficiency. Inserting furan moieties in the backbone of the conjugated polymer enables the use of less-bulky solubilizing side-chains, owing to the significant contribution of the furan rings to overall polymer solubility in organic solvents. Tuning side-chain design is shown to affect thin-film nanostructural order. Bulk heterojunction solar cells fabricated from furan-containing polymers and the electron-acceptor PC71BM exhibit power conversion efficiencies exceeding 5.0%.