The role of functional moieties on carbon nanotube surfaces in solar energy conversion.

An easily dispersible multiwalled carbon nanotube (MWCNT) derivative is prepared, and provides a platform for the synthesis of the phenyl butyric acid methyl ester (PCBM) analog. The carbene addition reaction of MWCNTs makes derivatives that are less soluble in organic solvents; by exploiting this differential solubility, PCBM analogs can be separated from the unreacted functionalized MWCNTs. Our experimental evidences indicate that it is the unique properties of the butyric acid methyl ester moiety that makes the acceptor material perform better in organic photovoltaics (OPVs). Studying the combination of the butyric acid methyl ester moiety and the deagglomerated functionalized MWCNT structures provides us an insight into nanoscale charge transfer and transportation inside the donor-acceptor domain. It is demonstrated that a strong structure-property relationship exists for the functionalized MWCNTs, which enables us to correlate the functionality on the carbon nanostructures with performance in OPVs.