Assembly of carbon nanotubes and alkylated fullerenes: nanocarbon hybrid towards photovoltaic applications

Taking advantage of the non-covalent interaction between alkyl chains and the sidewalls of a single-walled carbon nanotube (SWCNT), a nanocarbon hybrid of SWCNT and a fullerene (C-60) derivative with long alkyl chains was constructed as a donor-acceptor pair for photovoltaics and nanodevice investigations. It was found that SWCNT could be mostly unbundled by the alkylated C-60 (1) and was well-dispersed in organic solvents. As a photoactive material, the resultant nanocarbon hybrid, 1-SWCNT, performed well in light-energy harvesting applications in photoelectrochemical cells and nanoscale field-effect transistors (FET). Moreover, the 1-SWCNT assembly exhibited superhydrophobicity, providing an interesting opportunity to fabricate nanocarbon-based waterproof optoelectronic devices. In order to understand the photoexcitation process, the 1-SWCNT assembly was electrochemically and spectroscopically characterized. The electrochemical results showed that the SWCNT facilitated electronic communication between 1 and the electrode. The steady-state and time-resolved fluorescence and the photoluminescence excitation studies suggested efficient quenching of the singlet excited state of C-60. Nanosecond transient absorption data revealed the one-electron reduction of fullerene, C-60(center dot-), thereby demonstrating the photoinduced electron transfer from SWCNT to the C-60 unit in the 1-SWCNT assembly.