Robin Nicholas

Abstract:

We have investigated the ultrafast far-infrared transmission of isolated single-walled carbon nanotubes using optical-pump THz-probe spectroscopy. The THz dielectric response is dominated by excitons with an initial, rapid decay due to Auger recombination followed by a slow decay of isolated single excitons. Frequencydependent analysis of the photomduced dielectric function suggest an internal excitonic excitation at ∼11 meV with further low-frequency (∼0.6 and 1.4 THz) absorption features at high densities ascribed to exciton complexes. A featureless conductivity bleaching is attributed to an exciton-induced reduction in the mobility of free carriers caused by phase-space filling. © 2009 American Chemical Society.

Abstract:

We report a study of the electronic properties of the heterojunction between regioregular poly(3-hexylthiophene) (rrP3HT) and single-walled carbon nanotubes (SWNTs). Comparison of the spectroscopic data of nanotube dispersions in a range of polymers indicates significant changes in the nature of the observed SWNT excitons only in combination with rrP3HT. A detailed analysis concludes that a type II heterojunction between rrP3HT and small diameter s-SWNTs is formed, making these particular nanohybrids a promising material for organic photovoltaics.