Extracting Charge Carrier Scattering Information in Thermoelectric Materials within the Framework of a Single Parabolic Band Model

Charge carrier scattering in thermoelectric (TE) materials at room temperature and above is typically assumed to be due to acoustic phonons. However, recent studies indicate that this assumption needs to be taken with caution in many thermoelectric materials, as mechanisms such as polar optical phonon scattering and ionized impurity scattering can play an important role. In this work, we show that scattering information can be extracted from temperature-dependent TE data (Seebeck coefficient, electrical conductivity, and Hall coefficient) using standard multivariable optimization algorithms. Investigation of the scattering processes relies on the differences in their temperature and energy dependencies, which manifest as a variation of the absolute values and temperature slopes of the TE properties. Four major scattering processes, namely, scattering due to acoustic phonons, alloying, ionized impurities, and polar optic phonons, have been explored in this study. Standard analytical expressions for the scattering processes have been implemented within the framework of the Boltzmann transport equation, with the refined variables of interest being density of states mass, acoustic deformation potential, alloy scattering potential, and polar-optical phonon cutoff frequency. For the current study, we have analyzed materials with charge transport dominated by a single parabolic band. The accuracy of the predicted data was checked for a large range of parameters and carrier concentration values. Results indicate that the mean deviation in all of the parameters is less than 1%. Since no prior information about the refined parameters is necessary, the proposed technique can be a handy tool for identifying the dominant carrier scattering mechanisms in thermoelectric materials.