Theory and it ab initio calculation of radiative lifetime of excitons in semiconducting carbon nanotubes

TL;DR

This paper combines theoretical analysis and first-principles calculations to determine the radiative lifetime of excitons in semiconducting carbon nanotubes, revealing intrinsic and effective lifetimes influenced by exciton momentum and dark states.

Contribution

It provides the first ab initio calculations of exciton radiative lifetimes in carbon nanotubes, accounting for dark-bright exciton interactions and temperature effects.

Findings

Intrinsic lifetime of ~10 ps for bright excitons

Effective lifetime of ~10 ns at room temperature

Dark excitons significantly influence measured lifetimes

Abstract

We present theoretical analysis and first-principles calculation of the radiative lifetime of excitons in semiconducting carbon nanotubes. An intrinsic lifetime of the order of 10 ps is computed for the lowest optically active bright excitons. The intrinsic lifetime is however a rapid increasing function of the exciton momentum. Moreover, the electronic structure of the nanotubes dictates the existence of dark excitons nearby in energy to each bright exciton. Both effects strongly influence measured lifetime. Assuming a thermal occupation of bright and dark exciton bands, we find an effective lifetime of the order of 10 ns at room temperature, in good accord with recent experiments.