Effective atomic interface engineering in Bi2Te2.7Se0.3 thermoelectric material by atomic-layer-deposition approach

Grain boundaries play a critical role in the carrier/phonon transport in thermoelectric materials. It remains a big challenge to control over both chemical composition and dimension of grain boundary precisely by traditional approaches. Herein, an bottom-up grain boundary engineering strategy based on atomic layer deposition (ALD) is first introduced to atomically control and modify the grain boundary of Bi2Te3-based thermoelectric materials. To demonstrate the effect of this strategy, ultrathin ZnO interlayer is deposited on the Bi2Te2.7Se0.3 (BTS) grain boundaries to optimize of the carrier/phonon transport for achieving high thermoelectric performance. In situ TEM experiments upon heating reveals that the ZnO interlayer will give rise to the precipitation of Te nanodot at ZnO/BTS interface, which can be atomically controlled by adjusting the thickness of ZnO layer. Benefited from the atomically precise modified grain boundary, a maximum ZT of 0.85 is obtained, approximately 1.8 times higher than that of the pure BTS. As a powerful interfacial modification strategy, ALD-based approach can be extended to other thermoelectric material system simply, which may contribute to the development of high performance thermoelectric material of great significance.