Diffusive and Unimolecular Nonradiative Decay of Excited States in Doped Carbon Nanotubes

Doping can profoundly affect the electronic- and optical-structure of semiconductors. Here we address the effect of surplus charges on non-radiative (NR) exciton and trion decay in doped semiconducting single-wall carbon nanotubes. The dependence of exciton photoluminescence quantum yields and exciton decay on the doping level, with its characteristically stretched-exponential kinetics, is attributed to diffusion-limited NR decay at charged impurity sites. By contrast, trion decay is unimolecular with a rate constant of $2.0\,\rm ps^{-1}$. Our experiments thus show that charged impurities not only trap trions and scavenge mobile excitons but that they also facilitate efficient NR energy dissipation for both.

Klaus H. Eckstein, Pascal Kunkel, Markus Voelckel, Friedrich Schöppler, Abasi Abudulimu, Larry Lüer, Tobias Hertel · 2021