Title: Boosting the power factor with resonant states: a model study,
Abstract: A particularly promising pathway to enhance the efficiency of thermoelectric
materials lies in the use of resonant states, as suggested by experimentalists
and theorists alike. In this paper, we go over the mechanisms used in the
literature to explain how resonant levels affect the thermoelectric properties,
and we suggest that the effects of hybridization are crucial yet
ill-understood. In order to get a good grasp of the physical picture and to
draw guidelines for thermoelectric enhancement, we use a tight-binding model
containing a conduction band hybridized with a flat band. We find that the
conductivity is suppressed in a wide energy range near the resonance, but that
the Seebeck coefficient can be boosted for strong enough hybridization, thus
allowing for a significant increase of the power factor. The Seebeck
coefficient can also display a sign change as the Fermi level crosses the
resonance. Our results suggest that in order to boost the power factor, the
hybridization strength must not be too low, the resonant level must not be too
close to the conduction (or valence) band edge, and the Fermi level must be
located around, but not inside, the resonant peak.