title: Codoping in SnTe: Enhancement of Thermoelectric Performance through Synergy of Resonance Levels and Band Convergence.
abstract: We report a significant enhancement of the thermoelectric performance of p-type SnTe over a broad temperature plateau with a peak ZT value of ∼1.4 at 923 K through In/Cd codoping and a CdS nanostructuring approach. Indium and cadmium play different but complementary roles in modifying the valence band structure of SnTe. Specifically, In-doping introduces resonant levels inside the valence bands, leading to a considerably improved Seebeck coefficient at low temperature. Cd-doping, however, increases the Seebeck coefficient of SnTe remarkably in the mid- to high-temperature region via a convergence of the light and heavy hole bands and an enlargement of the band gap. Combining the two dopants in SnTe yields enhanced Seebeck coefficient and power factor over a wide temperature range due to the synergy of resonance levels and valence band convergence, as demonstrated by the Pisarenko plot and supported by first-principles band structure calculations. Moreover, these codoped samples can be hierarchically structured on all scales (atomic point defects by doping, nanoscale precipitations by CdS nanostructuring, and mesoscale grains by SPS treatment) to achieve highly effective phonon scattering leading to strongly reduced thermal conductivities. In addition to the high maximum ZT the resultant large average ZT of ∼0.8 between 300 and 923 K makes SnTe an attractive p-type material for high-temperature thermoelectric power generation.
authors: Gangjian
authors: G
authors: Tan
authors: Fengyuan
authors: F
authors: Shi
authors: Shiqiang
authors: S
authors: Hao
authors: §Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, United States.
authors: Hang
authors: H
authors: Chi
authors: Li-Dong
authors: LD
authors: Zhao
authors: §Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, United States.
authors: Ctirad
authors: C
authors: Uher
authors: Chris
authors: C
authors: Wolverton
authors: Vinayak P
authors: VP
authors: Dravid
authors: ∥Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States.
authors: Mercouri G
authors: MG
authors: Kanatzidis