4.8 Article

Enabling High Quality Factor and Enhanced Thermoelectric Performance in BiBr3-Doped Sn0.93Mn0.1Te via Band Convergence and Band Sharpening

Journal

ACS APPLIED MATERIALS & INTERFACES
Volume 14, Issue 28, Pages 32236-32243

Publisher

AMER CHEMICAL SOC
DOI: 10.1021/acsami.2c06822

Keywords

band convergence; band sharpening; carrier mobility; thermoelectric; SnTe

Funding

  1. National Key Research and Development Program of China [2017YFF0204706]
  2. Fundamental Research Funds for the Central Universities [FRF-MP-18-005, FRF-MP-19-005]
  3. Micronano Fabrication Technology Department, Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China

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Lead-free SnTe-based materials, achieved through alloying with Mn and doping with BiBr3, demonstrate significantly improved power factor and quality factor, making them promising alternatives to PbTe.
ABSTRACT: Lead-free SnTe-based materials are expected to replace PbTe and have gained much attention from the thermoelectric community. In this work, a maximum ZT of -1.31 at 873 K is attained in SnTe via promoting a high quality factor resulting from Mn alloying and BiBr3 doping. The results show that Mn alloying in SnTe converges the L band and the n-ary sumation band in valence bands to supply enhanced valley degeneracy and the density of states effective mass, giving rise to a high power factor of -21.67 mu W cm-1 K-2 at 723 K in Sn0.93Mn0.1Te. In addition, the subsequent BiBr3 doping can sharpen the top of the valence band to coordinate the contradiction between the band effective mass and the carrier mobility, thus enhancing the carrier mobility while maintaining a relatively large density of states effective mass. Consequently, a maximum power factor of 23.85 mu W cm-1 K-2 at 873 K is achieved in Sn0.93Mn0.1Te-0.8 atom % BiBr3. In addition to band sharpening, BiBr3 doping can also effectively suppress the bipolar effect at elevated temperatures and reduce the lattice thermal conductivity by strengthening the point defect phonon scattering. Benefitting from doping BiBr3 in Sn0.93Mn0.1Te optimizes the carrier mobility and suppresses the lattice thermal conductivity, resulting in a dramatically enhanced quality factor. Accordingly, an average ZT of -0.62 in the temperature range of 300-873 K is obtained in Sn0.93Mn0.1Te-0.8 atom % BiBr3, -250% increase compared with that in Sn1.03Te.

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