  The power factor of a thermoelectric device is a measure of the
heat-to-energy conversion efficiency in nanoscopic devices. Yet, even as
interest in low-dimensional thermoelectric materials has increased,
experimental research on what influences the power factor in these systems is
scarce. Here, we present a detailed thermoelectric study of graphene quantum
dot devices. We show that spin-degeneracy of the quantum dot states has a
significant impact on the zero-bias conductance of the device and leads to an
increase of the power factor. Conversely, we demonstrate that non-ideal heat
exchange within the leads can suppress the power factor near the charge
degeneracy point and non-trivially influences its temperature dependence.
