Boron-Mediated Interface Engineering for Enhancing The Thermoelectric Performance of Bi₂Te_2.7Se_0.3 Films

Nanostructuring has become one of the most practically proven and effective strategies in enhancing the thermoelectric figure of merit, which significantly propels thermoelectric materials to the forefront of progress in fundamental research and advanced applications. Accompanied by nanostructuring, heterogenization, which frequently shows excellent synergistic effects with nanostructures, has appeared as an appendable and feasible solution for a further breakthrough.<br/>Hexagonal boron nitride (h-BN), exhibiting remarkable thermal and chemical stability, is a potential candidate as the heterogeneous additive since the thermal conductivity of a single h-BN is much lower than that of graphene. In this work, to improve the thermoelectric properties of Bi₂Te_2.7Se_0.3 (BTS) thin films, BTS and h-BN were co-deposited on a SiO₂/Si substrate by a dual-beam laser system. The BN addition is expected to synergistically optimize the thermoelectric properties and stability of the BTS films.<br/>According to the x-ray diffraction, the crystal structure of the formed BTS:BN hetero-nanostructured films deposited at a temperature higher than 400 °C shows a preferred orientation of (00<i>l</i>), which significantly improves the carrier mobility (~105 cm²V^-1s^-1). The optimized Seebeck coefficient is −197 μVK^-1, and the corresponding power factor is 29 µWcm^-1K^-2. Raman spectroscopy was performed to analyze the thermal transporting of the formed BTS:BN films. A non-local thermal equilibrium phenomenon of Raman signal collapse at lower laser energy was found, indicating that introducing the BN additive can effectively reduce the thermal conduction of the BTS films and, thus, can effectively improve the thermoelectric performance.