Thermoelectric Properties of Lead-free Ba₃NBr₃ Perovskites: Insights from DFT Calculation

In recent years, perovskites have attracted considerable interest in the field of thermoelectric owing to their outstanding properties, such as excellent carrier mobility, high power factors, and very low thermal conductivity. In this study, we investigate the thermoelectric performance of Ba₃NBr₃ perovskites through first-principles calculations. The optimized lattice parameter is found to be 6.65 Å. The band structure analysis confirms the semiconducting nature of the material with a direct bandgap of 1.17 eV. The material exhibits a peak Seebeck coefficient of 0.809 mV=K. We also evaluated the relaxation times and observed that p-type carriers have a longer relaxation time than n-type carriers under certain temperature conditions. The electrical and thermal conductivity demonstrate intriguing trends — around the Fermi level, n-type conductivity initially dominates at a specific temperature; however, with increased doping, the p-type conductivity surpasses that of n-type carriers. At 300 K, the lattice thermal conductivity is found to be 1.5 W=m·K. The synergy of high Seebeck coefficient, substantial electrical conductivity, and relatively low thermal conductivity leads to a promising figure of merit (ZT) of 0.724 for Ba₃NBr₃. These results suggest that Ba₃NBr₃ holds strong potential for use in thermoelectric applications, making it a valuable material for further research and practical implementation.