Semiconducting single-walled carbon nanotubes (SWCNTs) are attractive earth-abundant materials for solar energy conversion because they offer a wide range of band gaps to harness the solar spectrum. Absorption of light in a SWCNT creates delocalized, bound electron hole pairs (excitons), which must be efficiently separated into charges by dissociation at a Type II (donor:acceptor) heterojunction. SWCNT:fullerene bilayers are useful as donor-acceptor model systems to study the kinetics and energetics of exciton dissociation and photoinduced electron transfer. In this work, time resolved microwave conductivity was used to link the amount of free charges generated at different SWCNT/fullerene bilayer heterojunctions with the driving force for exciton dissociation as a function of SWCNT diameter and fullerene cage modification. By modifying the fullerene cage with different numbers of CF<sub>3</sub> groups the resulting electron affinity and driving force for exciton dissociation was tuned. A clear inverted region was observed for two SWCNT thin films with dramatically different average diameter (linked to the band gap, electron affinity, and ionization potential), indicating the reorganization energy plays an important role in the energetics of exciton dissociation. Garnering the full potential of SWCNTs as solar absorbers will rely on a strong understanding of exciton dissociation in these novel material systems.

Time resolved microwave conductivity on single-walled carbon nanotube fullerene heterojunctions

249th National Meeting (2015)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.