Ab initio study of electron mean free paths and thermoelectric properties of lead telluride

By adopting a state-of-art first-principles calculation scheme on electron-phonon interaction in n-type PbTe, we are able to demonstrate the energy-resolved electron mean free path for different temperatures and the power factor obtained by only considering electrons with mean free path up to certain value. There exists a specific mean free path, corresponding to that of the electrons at the chemical potential, below which electrons contribute positively to the power factor while longer mean free path electrons contribute negatively to the power factor. As a result, there is an optimum mean free path which gives rise to the maximum truncated power factor.