Manipulation of charge transport in thermoelectrics

While numerous improvements have been achieved in thermoelectric materials by reducing the lattice thermal conductivity ( κ L ), electronic approaches for enhancement can be as effective, or even more. A key challenge is decoupling Seebeck coefficient ( S ) from electrical conductivity ( σ ). The first order approximation - a single parabolic band assumption with acoustic scattering - leads the thermoelectric power factor ( S 2 σ ) to be maximized at a constant reduced Fermi level ( η ~ 0.67) and therefore at a given S of ~167 μV/K. This simplifies the challenge of maximization of σ at a constant η , leading to a large number of degenerate transport channels (band degeneracy, N v ) and a fast transportation of charges (carrier mobility, μ ). In this paper, existing efforts on this issue are summarized and future prospectives are given.