  Doping substantially influences the electronic and photophysical properties
of semiconducting single-wall carbon nanotubes (s-SWNTs). Although prior
studies have noted that surplus charge carriers modify optical spectra and
accelerate non-radiative exciton decay in doped s-SWNTs, a direct mechanistic
correlation of trion formation, exciton dynamics and energetics remains
elusive. This work examines the influence of doping-induced non-radiative decay
and exciton confinement on s-SWNT photophysics. Using photoluminescence,
continuous-wave absorption, and pump-probe spectroscopy, we show that
localization of and barrier formation by trapped charges can be jointly
quantified using diffusive exciton transport- and particle-in-the-box models,
yielding a one-to-one correlation between charge carrier concentrations derived
from these models. The study highlights the multifaceted role of exohedral
counterions, which trap charges to create quenching sites, form barriers to
exciton movement, and host trion states. This contributes significantly to
understanding and optimizing the photophysical properties of doped SWNTs.
