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

This study reports a strategy to enhance the thermoelectric performance of Bi₂Te_2.7Se_0.3 (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.