  Organic materials have attracted recent interest as thermoelectric (TE)
converters due to their low cost and ease of fabrication. We examine the
effects of disorder on the TE properties of semiconducting polymers based on
the Gaussian disorder model (GDM) for site energies while employing Pauli's
master equation approach to model hopping between localized sites. Our model is
in good agreement with experimental results and a useful tool to study hopping
transport. We show that stronger overlap between sites can improve the
electrical conductivity without adversely affecting the Seebeck coefficient. We
find that positional disorder aids the formation of new conduction paths with
an increased probability of carriers in high energy sites leading to a
simultaneous increase in electrical conductivity and Seebeck coefficient. On
the other hand, energetic disorder leads to increased energy gap between sites,
hindering transport, and adversely affects both conductivity and Seebeck.
Furthermore, positional correlation primarily affects conductivity, while
correlation in energy has no effect on TE properties of polymers. Our results
also show that the Lorenz number increases with Seebeck coefficient, largely
deviating from the Sommerfeld value, in agreement with experiments and in
contrast to band conductors. We conclude that reducing energetic disorder while
increasing positional disorder can lead to higher TE power factors.
