Temperature effects on femtosecond transient absorption kinetics of semiconducting single-walled carbon nanotubes.

We report femtosecond transient absorption kinetics measured for selected semiconducting single-walled carbon nanotubes at different temperatures between 77 and 290 K. The nanotubes are embedded in a thin polymethylmethacrylate film, and the dominance of individual species enabled to probe selectively the kinetics associated with two desired tube types, the (6,5) and (7,5) tubes. A strikingly similar temperature dependence is found between the maximum change in the amplitude of transient absorption kinetics, the overall decay time and steady-state fluorescence emission intensity. The simplest explanation for our data is that the temperature dependence of the fluorescence intensity and the exciton decay kinetics are dominated by nonradiative decay and that the radiative decay rate is weakly temperature dependent.