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

TL;DR

This study investigates how doping affects non-radiative decay processes of excitons and trions in semiconducting carbon nanotubes, revealing diffusion-limited decay for excitons and unimolecular decay for trions.

Contribution

It provides new insights into the decay mechanisms of excitons and trions in doped carbon nanotubes, highlighting the role of charged impurities in non-radiative energy dissipation.

Findings

Doping influences exciton photoluminescence quantum yields.

Exciton decay exhibits stretched-exponential kinetics due to diffusion-limited processes.

Trion decay is unimolecular with a rate constant of 2.0 ps^{-1}.

Abstract

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.