  Highly oriented polymer films can show considerable anisotropy in the
thermoelectric properties leading to power factors beyond those predicted by
the widely obeyed power law linking the thermopower $S$ and the electrical
conductivity $\sigma$ as $S\propto\sigma^{-1/4}$. This has led to encouraging
practical results with respect to the electrical conductivity, notwithstanding
that the conditions necessary to enhance $\sigma$ and $S$ simultaneously are
less clear. Here, kinetic Monte Carlo simulations are used to study the impact
of structural anisotropy on the thermoelectric properties of disordered organic
semiconductors. We find that stretching is a suitable strategy to improve the
conductivity along the direction of strain, while the effect on the power
factor depends on the morphology the polymer crystallizes. In general,
crystalline polymers show a simultaneous increase in $\sigma$ and $S$ which is
not the case for amorphous polymers. Moreover, we show that the trends
resulting from simulations based on variable-range hopping are in good
agreement with experiments and can describe the different functional
dependencies in the $S$ versus $\sigma$ behaviour of different directions.
