  We theoretically and numerically investigate the capability of disordered
media to enhance the optical path length in dielectric slabs and augment their
light absorption efficiency due to scattering. We first perform a series of
Monte Carlo simulations of random walks to determine the path length
distribution in weakly to strongly (single to multiple) scattering,
non-absorbing dielectric slabs under normally incident light and derive
analytical expressions for the path length enhancement in these two limits.
Quite interestingly, while multiple scattering is expected to produce long
optical paths, we find that media containing a vanishingly small amount of
scatterers can still provide high path length enhancements due to the very long
trajectories sustained by total internal reflection at the slab interfaces. The
path length distributions are then used to calculate the light absorption
efficiency of media with varying absorption coefficients. We find that maximum
absorption enhancement is obtained at an optimal scattering strength,
in-between the single-scattering and the diffusive (strong multiple-scattering)
regimes. This study can guide experimentalists towards more efficient and
potentially low-cost solutions in photovoltaic technologies.
