Interplay between metavalent bonds and dopant orbitals enables the design of SnTe thermoelectrics

• Published in: Nature communications Vol. 15; no. 1; pp. 9133 - 13
• Main Authors: Tang, Guodong, Liu, Yuqi, Yang, Xiaoyu, Zhang, Yongsheng, Nan, Pengfei, Ying, Pan, Gong, Yaru, Zhang, Xuemei, Ge, Binghui, Lin, Nan, Miao, Xuefei, Song, Kun, Schön, Carl-Friedrich, Cagnoni, Matteo, Kim, Dasol, Yu, Yuan, Wuttig, Matthias
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 23.10.2024; Nature Publishing Group; Nature Portfolio
• Subjects: 140/58; 147/143; 639/301/299/2736; 639/766/119/1000; Bonding; Brillouin zones; Carrier density; Density of states; Dislocation density; Dopants; Doping; Electron states; Electrons; Fermi level; Humanities and Social Sciences; multidisciplinary; Orbitals; Science; Science (multidisciplinary); Thermoelectric materials; Tin tellurides; Valence band
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-53599-2

Engineering the electronic band structures upon doping is crucial to improve the thermoelectric performance of materials. Understanding how dopants influence the electronic states near the Fermi level is thus a prerequisite to precisely tune band structures. Here, we demonstrate that the Sn-s states in SnTe contribute to the density of states at the top of the valence band. This is a consequence of the half-filled p-p σ-bond (metavalent bonding) and its resulting symmetry of the orbital phases at the valence band maximum (L point of the Brillouin zone). This insight provides a recipe for identifying superior dopants. The overlap between the dopant s- and the Te p-state is maximized, if the spatial overlap of both orbitals is maximized and their energetic difference is minimized. This simple design rule has enabled us to screen out Al as a very efficient dopant to enhance the local density of states for SnTe. In conjunction with doping Sb to tune the carrier concentration and alloying with AgBiTe 2 to promote band convergence, as well as introducing dislocations to impede phonon propagation, a record-high average ZT of 1.15 between 300 and 873 K and a large ZT of 0.36 at 300 K is achieved in Sn 0.8 Al 0.08 Sb 0.15 Te-4%AgBiTe 2 . The occupied anti-bonding states at the Fermi level in metavalently bonded systems stems from the interplay between metavalent bonds and the phase of orbitals. This provides a recipe for identifying superior dopants to improve the thermoelectric performance of metavalently bonded materials.