High Thermoelectric Performance in the Cubic Inorganic Cesium Iodide Perovskites CsBI₃ (B = Pb, Sn, and Ge) from First-Principles

Abstract

Searching thermoelectric materials with high performance and low cost is now receiving special attention and great challenges in the field of material design. In this work, we perform first-principles lattice dynamics combined with temperature-induced anharmonic phonon renormalization and connected to the Boltzmann transport equation to predict thermoelectric performance in the cubic inorganic iodide perovskites CsBI3 (B = Pb, Sn, and Ge) at a high temperature of 700 K. Under stabilization of the cubic phase that exhibits strong anharmonic phonon modes at 0 K, our calculations show that at T = 700 K, these perovskites have ultralow lattice thermal conductivities below 0.6 W m–1 K–1 and high thermopower factors over 1.5 mW m–1 K–2, being comparable or superior to those of GeTe. Moreover, we find that cubic CsGeI3 and CsSnI3 have higher thermoelectric figure of merit ZT over 0.95 upon n-type doping, being attributed to the strong lattice anharmonicity and flat-dispersive electronic bands with high degeneracy.

Superior thermoelectric properties of ternary chalcogenides CsAg5Q3 (Q = Te, Se) predicted using first-principles calculations

“…In the design of promising candidates for high performance TEMs, the primary interest was focused on innovative materials with intrinsically ultralow thermal conductivity. 19 Such ultralow thermal conductivity has been found in complex materials with complicated compositions 7,20,21 or disordered layered structures 22–26 and in simple crystalline materials such as halide perovskites 27–33 and dichalcogenides. 34–37 In these materials, the heat carriers are mostly phonons, being highly anharmonic, and strong phonon–phonon 27,38 or phonon-disorder scattering 39 is the main mechanism for lowering the thermal conductivity.…”

Anisotropic Chalcogenide Perovskite CaZrS3: A Promising Thermoelectric Material

“…For example, the ZT values of SnSe, Bi 2 O 2 Se, and LaCuOSe are reported to be about 2.6 at 923 K, 5.9 at 800 K, and 2.71 at 900 K, 26,28,61 respectively. Furthermore, the ZT value of CaZrS 3 is much higher than that of typical inorganic halide perovskites such as CsPbI 3 , CsSnI 3 , and CsGeI 3 , for which the maximum ZT values are reported to be 0.45, 0.95, and 1.05 at a stable temperature of 700 K, 62 respectively. Therefore, it suggested that the excellent TE performance of orthorhombic CaZrS 3 can be realized by adjusting the carrier concentration, indicating the potential to become an excellent TE material for CaZrS 3 .…”

Recent advances in designing thermoelectric materials

“…2 shows the maximum ZT achieved for bulk thermoelectric materials over the past six years as a function of temperature. 33–234…”