Enhancing thermoelectric properties of Sb ₂ Te ₃ flexible thin film through microstructure control and crystal preferential orientation engineering

Preparation of high performance flexible thermoelectric thin films would promote applications of flexible thermoelectric device. In this work, antimony telluride (Sb ₂ Te ₃ ) thin films were directly deposited on polyimide substrate. The crystalline structures and morphologies of the thin films were analyzed, and the mechanism of crystal growth influenced by sputtering pressure was discussed. We also investigated the effects of microstructure on their thermoelectric properties, where Hall effect measurement was conducted to provide further insight into the enhancement of thermoelectric properties. The mean free path of the carrier was calculated on the basis of carrier concentration and mobility. Our results showed that with (015) crystal preferential orientation, the electrical conductivity and Seebeck coefficient of Sb ₂ Te ₃ thin films were simultaneously increased, and a maximum power factor of 6.0 μW cm ⁻¹ K ⁻² was achieved, which was increased by 75% compared with the ordinary thin film. Meanwhile, due to the reduced lattice thermal conductivity and increased power factor, the estimated figure of merit (ZT) value was largely enhanced to 0.42.