Role of electron-phonon scattering on thermoelectric coefficients in pristine Cs2NaYbCl6 perovskite: A full DFT approach

Double-halide perovskites are recently attracting significant interest in the field of thermoelectric research due to the possibility of achieving very low thermal conductivity and retaining relatively high Seebeck coefficient and electrical conductivity. Accurate estimates of the transport related properties are, thus, highly desirable and are strictly linked to an extremely detailed characterization of the microscopic mechanism underlying the transport itself. To address this issue, in this study we conduct a comprehensive theoretical investigation of one of the main process-limiting carrier transports, i.e., electron-phonon scattering, in a typical double-halide perovskite, Cs2NaYbCl6. In order to quantify the specific magnitude of this process, we adopt in this study a comprehensive DFT analysis, with a focus on evaluating the resulting lifetimes (in both hole- and electron-mediated regimes), by solving iteratively the linearized Boltzmann equation. Using the evaluated lifetimes, we found distinct differences in electrical mobilities and Seebeck coefficient as a function of the temperature and carrier concentrations, revealing that the thermoelectric figure-of-merit ZT, while quite low, is significantly higher in the case of electron-mediated regime.