Photoconductivity of packed homotype bundles formed by aligned single-walled carbon nanotubes

Photoconductivity properties of aggregated single-walled carbon nanotubes have been studied by performing measurements on macroscopic ribbons, obtained by the aggregation of a large number of SWCNT bundles. Structural analysis performed by electron diffraction revealed that the nanotubes forming each bundle have the same chirality. The experimental results, regarding the region 1.2-3.6 eV and the pressure range 10(3)-10(-3) mbar, suggest that the photoexcitation of nanotubes, packed in bundles and organized in ribbons, generates electron-hole pairs within a band structure and that bond excitons are formed by Coulomb interactions between spatially confined charge carriers.