Synergetic optimization of electronic and thermal transport for high-performance thermoelectric GeSe–AgSbTe2 alloy

Abstract

Rhombohedral GeSe is a promising p-type thermoelectric material with a multivalley band structure. However, its figure of merit ZT, especially average ZT is still relatively low compared with the state-of-art thermoelectric materials. Here, we show that alloying with AgSbTe₂ can synergistically optimize the electronic and thermal transport properties of GeSe. On one hand, alloying can tune the crystal field and promote the band convergence between the lower light valence band and higher heavy valence band. The rising light valence band maximum increases both the density of state effective mass and carrier mobility, leading to a significantly improved power factor. On the other hand, the phonon scattering is also enhanced by the alloying effect, resulting in a low lattice thermal conductivity of 0.7 W m⁻¹K⁻¹ at 754 K. A peak ZT of ≈1.0 at 754 K was achieved in GeSeAg_0.2Sb_0.2Te_0.4 and more importantly, the ZT_avg (0.65) between 301 K and 754 K was improved by more than 56% compared to GeSeAg_0.2Sb_0.2Se_0.4 (ZT_avg = 0.41).