  Luminescent solar concentrators (LSCs) are devices that trap a portion of the
solar spectrum and funnel it towards photon harvesting devices. The modelling
of LSCs at a quantum chemical level however, remains a challenge due to the
complexity of exciton and photon dynamic modelling. This study examines singlet
exciton dynamics occurring within a typical LSC device. To do this, we use a
rejection-free kinetic Monte Carlo method to predict diffusion lengths,
diffusion coefficients, substrate anisotropy, and average exciton lifetimes of
perylene diimide (PDI) and tetracene based substrates in the low concentration
scheme. \textit{Ab initio} rate constants are computed using time-dependant
density functional theory based methods. PDI type substrates are observed to
display enhanced singlet exciton transport properties when compared to
tetracene. Simulations show that substrates with dipole-aligned chromophores
are characterised by anisotropic exciton diffusion, with slightly improved
transport properties. Finally, a PDI-tetracene substrate is simulated for both
disordered and dipole-aligned chromophore configurations. In this multi-dopant
substrate transport is predominantly mediated by PDI due to the asymmetry in
the transport rates between the two dyes considered. We conclude discussing the
properties of multi-dopant substrates and how they can impact the design of
next generation LSCs.
