High thermoelectric performance of p-type Bi0.5Sb1.5Te3 films on flexible substrate

Abstract

Bi2Te3-based compounds are excellent candidates for the low-temperature thermoelectric application. In the present work, a technology for fabrication of p-Bi0.5Sb1.5Te3 films with high thermoelectric efficiency on a thin flexible polyimide substrate has been developed. The preparation of films was carried out by a flash evaporation method. A systematic study of the transport properties (Hall coefficient, Seebeck coefficient, electrical conductivity, transverse Nernst coefficient) over the entire temperature range of 80–400 K for p-Bi0.5Sb1.5Te3 films has been performed. The power factor (PF) for the Bi0.5Sb1.5Te3 (doped by 0.5 wt % Te) film reaches the value of ~30.4 μW cm−1K−2, which is among the highest values of the PF reported in the literature to date for a film on a flexible polyimide (amorphous) substrate. The measured thermal diffusivity along the film allowed us to accurately estimate the figure of merit Z for p-Bi0.5Sb1.5Te3 films considering the anisotropic effect of Bi2Te3-based materials. A significant enhancement of Z up to ~3.0 × 10−3 K has been obtained for these films, which is state-of-the-art even compared to bulk materials. This research can provide insight into the fabrication of p-type branch of the Film Thermoelectric Modules (FTEM), which could be a candidate for application in micro-scale thermoelectric generators.