Carrier concentration control and thermoelectric enhancement of n-type Bi2Te3-based materials via atomic-layer-deposited In2O3 interfacial layers

Abstract

This study reports a strategy to enhance the thermoelectric performance of Bi2Te2.7Se0.3 (BTS) by introducing ultrathin In2O3 interfacial layers via atomic layer deposition (ALD). Conformal In2O3 coatings were preserved after spark plasma sintering, thereby suppressing grain growth. A small interfacial energy barrier (∼0.2 eV) was formed at the BTS/In2O3 interface, enabling carrier filtering that preferentially transmits high-energy electrons, thereby enhancing mobility. At the same time, the coatings suppressed Te volatilization during sintering, leading to reduced carrier concentration and increased Seebeck coefficient. Although electrical conductivity decreased, the power factor remained nearly unchanged, while total thermal conductivity was markedly reduced due to a lower electronic contribution. As a result, the 20-cycle In2O3-coated BTS achieved a maximum zT of 1.02 at 373 K, surpassing the pristine sample. These results highlight ALD-engineered interfacial barriers as an effective approach for carrier concentration control and thermoelectric performance optimization in bulk Bi2Te3-based materials.