Temperature behavior of the photoluminescence decay of semiconducting carbon nanotubes: The effective lifetime

Abstract

The temperature dependence of the photoluminescence decay of excitons in single-walled carbon nanotubes was measured for two nanotube species, (7,6) and (7,5), representative of the two nanotube $(n\ensuremath{-}m)\mathrm{mod}\phantom{\rule{0.2em}{0ex}}3$ families. A monotonic increase of the photoluminescence lifetime with decreasing temperature is observed. The external strain induced by lowering the temperature below the freezing point of the solution leads to an overall lowering of the photoluminescence lifetime. This effect indicates that the measured lifetime is defined by the intrinsic electronic properties of carbon nanotubes and could be understood as an exchange interaction between bright and dark excitonic states. We find the lifetime to vary between 223 and $319\phantom{\rule{0.3em}{0ex}}\mathrm{ps}$ between 290 and $5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, obtained by a multiexponential fit, well in agreement with previous experiments.