Intrinsic diffusion length of excitons in long single-walled carbon nanotubes from photoluminescence spectra

Abstract

Evaluation of intrinsic diffusion length of excitons in a long single-walled carbon nanotube (SWNT) is reported by analyzing the tube-length dependence of photoluminescence (PL) emission intensity. The PL emission intensities depending on the tube length are all obtained from one individual long SWNT suspended on a groove-patterned substrate. The exciton dynamics is described by a one-dimensional diffusion equation. The diffusion length in the clean and pristine long SWNTs is found to be constant, about 200 nm at a lower laser power regime, indicating an intrinsic diffusion behavior. The threshold laser power that is consistent with the onset of exciton-exciton annihilation is about 10${}^{21}$ photons/(cm${}^{2}$ s) for air-suspended SWNTs.