Multiple Exciton Generation in Chiral Carbon Nanotubes: Density Functional Theory Based Computation

TL;DR

This study employs density functional theory and many-body perturbation theory to model multiple exciton generation in chiral carbon nanotubes, predicting high quantum efficiency within the solar spectrum.

Contribution

It introduces a DFT-based computational approach to analyze exciton dynamics and MEG efficiency in specific chiral SWCNTs, advancing understanding of their optoelectronic properties.

Findings

Efficient MEG predicted in (6,2) and (6,5) SWCNTs within the solar spectrum.

Quantum efficiency reaches approximately 1.6 at about 3 times the electronic gap energy.

MEG onset occurs at twice the electronic gap energy.

Abstract

We use Boltzmann transport equation (BE) to study time evolution of a photo-excited state in a nanoparticle including phonon-mediated exciton relaxation and the multiple exciton generation (MEG) processes, such as exciton-to-biexciton multiplication and biexciton-to-exciton recombination. BE collision integrals are computed using Kadanoff-Baym-Keldysh many-body perturbation theory (MBPT) based on density functional theory (DFT) simulations, including exciton effects. We compute internal quantum efficiency (QE), which is the number of excitons generated from an absorbed photon in the course of the relaxation. We apply this approach to chiral single-wall carbon nanotubes (SWCNTs), such as (6,2), and (6,5). We predict efficient MEG in the (6,2) and (6,5) SWCNTs within the solar spectrum range starting at the $2 E_g$ energy threshold and with QE reaching $\sim 1.6$ at about $3 E_g,$ where $E_g$ is the electronic gap.