Ultrafast Exciton Energy Transfer in Bundles of Single-Walled Carbon Nanotubes

Excitation energy transfer is a long-lasting issue in the fields of photoscience and materials science encompassing physics, chemistry, and biology. We report femtosecond energy transfer of quasi-one-dimensional excitons in single-walled carbon nanotube bundles, which we investigate using time-resolved luminescence spectroscopy. Luminescence decay times are found to increase with decreasing photon energy from 1.2 to 0.6 eV. The energy-dependent decay behavior is analyzed using a simple rate equation based on the measured diameter distribution of the tubes. The rate of exciton energy transfer per nanotube from an excited semiconducting tube to adjacent semiconducting tubes [1.8−1.9(±0.2) × 10 12 s −1 ] is 1.6 times that of transfer to adjacent metallic tubes [1.1(±0.2) × 10 12 s −1 ]. The observed transfer rates are much lower than those predicted by the Förster model. This finding provides insight into the energy-transfer mechanisms of one-dimensional excitons.