Improved thermoelectric performance of n-type Bi-Te-Se thin films deposited on flexible polyimide substrates via SnSe cosputtering

Bi2Te2.7Se0.3 (BTS) is currently the most widely used n-type thermoelectric (TE) material at room temperature. However, the narrow bandgap and reduced density of states near the Fermi level limit its TE performance. Various elemental doping, including Sn and Se, has been proven effective to optimize the TE properties of the BTS bulks. Herein, the Sn and Se dopants were simultaneously introduced into the Bi-Te-Se films deposited on flexible polyimide substrates through magnetron cosputtering Bi2Te2.7Se0.3 and SnSe targets. The induced lattice distortions and compositional variation enhanced the carrier concentration, altered the electronic structure, and resulted in a distinct enhancement in the electrical transport properties. Finally, the Bi-Te-Se film containing 1.48 at. % Sn reveals the highest power factor of 523.8 μW m−1 K−2 at 500 K, representing a 24.1% enhancement compared to that in the undoped Bi-Te-Se film.