Main-Chain Fullerene Polymers for Photovoltaic Devices

International audienceA prototype for a new class of macromolecules with a high fraction of fullerene is proposed. Their facile synthesis, modular structure, electronic activity, and novel solid-state behavior make them promising materials for photovoltaic applications. Controlled reversible-deactivation radical additions of the sterically bulky 1,4-bis(methylcyclohexyl ether)-2,5-dibronlomethyl benzene to fullerene are indicated by GPC, NMR, and TGA Studies to yield oligomers and polymers containing C-60 in the main chain. UV and cyclic voltammetry indicate that the C60 undergoes mainly 1,4-additions and a minority (ca. 20%) of 1,2-additions to make a regio-irregular macromolecule. The same reaction performed in the presence of 1,4-bis(methylcyclohexyl ether)-2-bromomethyl benzene, resulting in macromolecules with bromomethyl-tree chain ends, permitted confirmation of the aforementioned characteristics. The unusual reptation of the poly {(1,4-fullerene)-alt-[14-dimethylene-2,5-bis(cyclohexylmethyl ether) phenylene]}s (PFDP) in an Al/Ca/poly(3-hexylthiophene)-blend-PFDP/PEDOT-blend-PSS/ITO/glass structured device is demonstrated by AFM to yield nanoclusters at a scale (ca. 20 run) favorable to exciton capture. Even without optimization of the chemical structure or the device, this prototype reached promising power conversion efficiencies of 1.6%