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