Enhanced Optical Properties of Single-Walled Carbon Nanotubes (via SP³-Hybridization Defects) from Many-Body Perturbation Theory Based on Density Functional Theory Calculations

The optical consequences of functionalized carbon nanotubes (CNTs) (via a pair of SP³-hybridized functional groups attached to a carbon ring) have been explored in great depth due to their promise of superior electronic properties for tunable emission in infrared energies. These studies have relied on time-dependent density functional theory (TD-DFT) calculations to model the excited states of these particles, but very little work has been completed on multiple exciton generation (MEG) processes within these systems. Here we employ a novel method based in non-equilibrium, finite-temperature, many-body perturbation theory (MBPT) calculations that utilize output from density functional theory (DFT) to accurately model excited states of these systems. We solve the Boltzmann transport equation (BE), including phonon absorption/emission and biexciton formation/recombination terms [1,2]. With this approach we compute an array of CNTs of varying chirality and functionalization scheme. We see that SP³-defect functionalization of pristine CNTs that had high-energy biexciton MEG thresholds (E ≈ 2.4E_g) can be reduced to 2E_g, which drastically increases their value as efficient multiple exciton sources.

[1] J. Chem. Phys. 147, 154106 (2017)
[2] J. Phys. Chem. Lett., 2018, 9, 19, 5759-5764