Understanding the electrical transports of p-type polycrystalline SnSe with effective medium theory

SnSe crystal is one of the most potential thermoelectric materials due to its excellent transport properties. The electrical conductivity of p-type SnSe crystal gradually decreases with increasing temperature, while that of the polycrystalline sample shows a completely different trend. We revealed that below 400 K, the existence of plentiful grain boundaries dominates the carrier scattering and determines the electrical transport of p-type polycrystalline SnSe, while at high temperatures, from 400 to 800 K, the electrical transport and conductivity curve still requires a clear understanding. In this study, by conducting the high-temperature synchrotron radiation x-ray diffraction (SR-XRD) measurements and refining the patterns, we obtained the phase fractions of Pnma and Cmcm phases in this temperature range. Using the derived single-phase theoretical electrical conductivity, combined with the self-consistent effective medium theory, the electrical conductivity of p-type polycrystalline SnSe between 400 and 800 K was simulated. This study provides a perspective and simulation method to understand the electrical transport of p-type polycrystalline SnSe.