Issue Date: January 9, 2012
Side-Chain Swap In Conducting Polymers
Scientists who create organic polymers for solar-cell applications can now boost nanostructural order more easily using linear alkyl side chains, rather than branched ones. These researchers have known that linear substituents in polymers used to make photovoltaic devices improve structural order by reducing π-π stacking distances between polymer backbones. But polymers with linear alkyl substituents tend to be less soluble—and therefore less amenable to solution processing—than their branched brethren. A team led by Jean M. J. Fréchet of the University of California, Berkeley, and King Abdullah University of Science & Technology, in Saudi Arabia, now reports that swapping furan units for some of the thiophene units in the backbone of such polymers produces a material that maintains its solubility, even with linear alkyl side chains (J. Am. Chem. Soc., DOI: 10.1021/ja2089662). Using a polymer dubbed PDPP2FT-C14, the researchers created a bulk heterojunction solar cell with an efficiency of 6.5%, which outperforms solar cells with similar polymers containing branched side chains or polymers with entirely thiophene-based backbones.
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