High temperature charge and thermal transport properties of the n-type thermoelectric material PbSe

TL;DR

This study investigates charge, optical, and thermal transport in n-type PbSe, revealing complex electron-phonon interactions, deviations in thermal conductivity at high temperatures, and promising thermoelectric performance at 700K.

Contribution

It provides new insights into high-temperature transport mechanisms and optical properties of n-type PbSe, highlighting complex electron-phonon interactions and optical phonon contributions to thermal conductivity.

Findings

Mobility-limiting scattering mechanism above 500 K.

Deviation from classical high-temperature thermal conductivity behavior.

Thermoelectric figure of merit of ~0.8 at 700K.

Abstract

We present a detailed study of the charge transport, optical reflectivity, and thermal transport properties of n-type PbSe crystals. A strong scattering, mobility-limiting mechanism was revealed to be at play at temperatures above 500 K. The mechanism is indicative of complex electron-phonon interactions that cannot be explained by conventional acoustical phonon scattering alone. We applied the first order non-parabolicity approximation to extract the density of states effective mass as a function of doping both at room temperature and at 700 K. The results are compared to those of a parabolic band model and in the light of doping dependent studies of the infrared optical reflectivity. The thermal conductivity behavior as a function of temperature shows strong deviation from the expected Debye-Peierls high temperature behavior (umklapp dominated) indicating an additional heat carrying channel, which we associate with optical phonon excitations. The correlation of the thermal conductivity observations to the high temperature carrier mobility behavior is discussed. The thermoelectric figure of merit exhibits a promising value of ~0.8 at 700K at 1.5 x 10^{19}$ cm^-3.