Strategies for the High Average zT in the Electron-Doped SnTe

Hyunjin Park, Kyu Hyoung Lee, Minsu Heo, Sang Il Kim, Hyun Sik Kim

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We propose a new strategy to achieve a high average zT in electron-doped SnTe by applying the two-band (TB) and single parabolic band (SPB) models to the electronic transport properties of Sn0.97M0.03Te (M=Ga, In, Bi, and Sb) reported in the literature. To achieve a high average zT at temperatures from 300 to 823 K, both zT at 300 and 823 K should be high with a steadily increasing zT over the temperatures. The p-type SnTe is known to have a light valence band and a heavy valence band that are approximately 0.40 eV apart. The Bi-doped SnTe exhibits one of the highest zT among all the other doped samples at 300 K (0.09) and the highest zT at 823 K (0.9), with a steadily increasing zT in between. The TB model confirms the presence of the resonant state at 300 K which is responsible for the high zT at 300 K. The B-factor, which is related to the theoretical maximum zT, calculated by the SPB model indicates a steady increase in zT with increasing temperature. The temperature-dependent B-factor of the Bi-doped SnTe suggests that the initial position of its Fermi level at 300 K calculated by the TB model may be responsible for the temperature coefficient of the B-factor, which determines the zT at 823 K. According to the SPB model, experimental zT of 0.9 of the Bi-doped SnTe can be further improved to 1.03 (14% improvement) at 823 K upon carrier concentration optimization. To achieve a high average zT in SnTe, electron doping with a dopant that forms a resonant state and placing the Fermi level at the light valence band in the vicinity of the heavy valence band maximum are both essential.

Original languageEnglish
Article number5512034
JournalInternational Journal of Energy Research
StatePublished - 2023


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