Issue 35, 2024

Burstein-moss effect leads to an unusual suppression of bipolar conduction with shrinking bandgap

Abstract

Thermoelectrics have shown promising applications in cooling, temperature management and waste heat recovery. However, the thermoelectric performance deteriorates when bipolar conduction intensifies, making it necessary to suppress this adverse effect for efficient thermoelectrics. Generally, increasing the bandgap (Eg) to inhibit intrinsic excitation through doping is widely accepted as an effective way to suppress bipolar conduction. However, we experimentally observed that intrinsic excitation and bipolar conduction are unusually suppressed as Eg narrows in indium-doped Bi2Te2Se. We attribute this unusual suppression to the Burstein–Moss effect through angle-resolved photoemission spectroscopy (ARPES) and transport tests. The Burstein–Moss effect suggests that the actual energy required for carrier excitation in degenerate semiconductors is the sum of Eg and the Fermi level shift (ΔEshift) rather than Eg alone, as we observed that after indium doping, Eg narrows but Eg + ΔEshift expands, accompanied by the suppression of intrinsic excitation and bipolar conduction. Our work emphasizes that when assessing and predicting the impact of a dopant on bipolar conduction, it is more appropriate to consider Eg + ΔEshift rather than Eg alone as Eg + ΔEshift is the actual energy required for intrinsic excitation. This physical law is important to thermoelectric materials as the Burstein–Moss effect is strongly intensified in narrow-bandgap degenerate semiconductors, which is precisely a common characteristic of typical thermoelectric materials.

Graphical abstract: Burstein-moss effect leads to an unusual suppression of bipolar conduction with shrinking bandgap

Supplementary files

Article information

Article type
Paper
Submitted
13 Jun 2024
Accepted
29 Jul 2024
First published
01 Aug 2024

J. Mater. Chem. A, 2024,12, 23670-23675

Burstein-moss effect leads to an unusual suppression of bipolar conduction with shrinking bandgap

C. Zhao, S. Cui, Y. Li, Y. Wu, T. Li, K. Li, L. Sun, Z. Sun, C. Xiao and Y. Xie, J. Mater. Chem. A, 2024, 12, 23670 DOI: 10.1039/D4TA04110K

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