Employing multi-functional SnSe inclusions to boost the thermoelectric performance of the shear-exfoliated Bi₂Te_2.7Se_0.3

Owing to the high near-room-temperature thermoelectric performance, Bi₂Te_2.7Se_0.3 (BTS)-based semiconductors have gained significant attention and acted as n-type materials in practical thermoelectric devices. To achieve higher thermoelectric performance in polycrystalline BTS, in this work, we employ SnSe as multifunctional micro/nanoinclusions via co-shear-exfoliating SnSe and BTS ingots and sintering the as-achieved hybrid powders into bulk materials. Experimental results indicate that the 2D-structured SnSe reduces the average size of shear-exfoliated BTS powders, leading to strengthened anisotropy of the as-sintered bulk materials, which can significantly improve the carrier mobility and in turn, the electrical conductivity. As well, introducing p-type SnSe into n-type BTS enhances the bipolar temperature of BTS, leading to higher Seebeck coefficients at higher temperatures, which contributes to a boosted power factor of >32 μW cm⁻¹ K⁻² at 448 K. Besides, the introduced SnSe micro/nanoinclusions with intrinsic low lattice thermal conductivities suppress the overall thermal conductivity of the hybrid bulk materials by providing denser phase boundaries in the matrix, and in turn strengthen the phonon scattering, which contributes to a competitive figure-of-merit ZT of ∼1.04 at 448 K and a high average ZT of 0.92, indicating the great potential for applying to practical devices.