The journey of tin chalcogenides towards high-performance thermoelectrics and topological materials

Lead chalcogenides and their alloys belong at the heart of thermoelectrics due to their large thermoelectric figure of merit (zT). However, recent research has shown a limitation in the use of lead (Pb)-based materials due to their toxicity and efforts have been made to produce non-toxic analogues of lead chalcogenides. Tin chalcogenides have been predicted to be promising for this purpose due to their unique electronic structure and phonon dispersion properties. Here, we discuss the journey of tin chalcogenides in the field of thermoelectrics and topological materials with the main emphasis on the bonding, crystal structures, electronic band structures, phonon dispersion and thermoelectric properties. The thermal transport properties of tin chalcogenides are explained based on lattice dynamics, where resonant bonding and local structural distortion play an important role in creating lattice anharmonicity, thereby lowering the lattice thermal conductivity. Since thermoelectric and topological materials, especially topological insulators and topological crystalline insulators, share similar material features, such as a narrow band gap, heavy constituent elements and significant spin-orbit coupling, we have discussed the thermoelectric properties of several topological tin chalcogenides from a chemistry perspective. This feature article serves as a useful reference for researchers who strive to improve the properties of tin chalcogenides and advance the field of thermoelectric and topological materials.