Remarkable thermoelectric efficiency of cubic antiperovskites Rb3X(Se & Te)I with strong anharmonicity

Abstract

This study reported a novel class of antiperovskites Rb₃X(Se & Te)I, which have strong lattice anharmonicity. Within this type of antiperovskite, we have achieved the separation of phonon and electron transport at the atomic level, allowing it to simultaneously meet low thermal conductivity and high electrical conductivity requirements. At room temperature, considering the quartic anharmonicity correction to phonon frequencies, the lattice thermal conductivities of Rb₃SeI and Rb₃TeI are only 0.44 W m⁻¹ K⁻¹ and 0.16 W m⁻¹ K⁻¹, making them excellent thermal insulating materials. At the same time, the nearly flat band and high degeneracy characteristics of the valence band maximum contribute to a high power factor in Rb₃X(Se & Te)I. At 800 K, the figure of merit ZT values of p-type doped Rb₃SeI and Rb₃TeI can reach 1.91 and 3.07, far exceeding those of traditional thermoelectric (TE) materials. These results not only reveal that Rb₃X(Se & Te)I is a class of high-performance TE materials but also provide new insights for the search and design of high-performance TE materials.