Anisotropy Control–Induced Unique Anisotropic Thermoelectric Performance in the n-Type Bi₂Te_2.7Se_0.3 Thin Films

Anisotropic Bi₂Te₃-based thermoelectric materials have drawn extensive interest in the past decades. Here, n-type Bi₂Te_2.7Se_0.3 films with superhigh figure of merit are developed through anisotropy control via tuning an external electric field and deposition anisotropy. It is found that the angle of interplanar grain boundaries between (0 1 5) and (0 1 11) planes can be tuned by the applied external electric field, which leads to the strengthened anisotropy of electron mobility and simultaneously maintains low lattice thermal conductivity. Dominated by the unique change in the anisotropy of both lattice thermal conductivity and electron mobility, a record-high zT value of ≈1.6 at room temperature can be achieved in the as-deposited n-type Bi₂Te_2.7Se_0.3 film under 20 V external electric field. This work indicates that the electric field–induced deposition anisotropy control can be used to develop high-performance Bi₂Te₃-based thermoelectric films.