Improving the thermoelectric performance of p-type (BixSb1−x)2Te3 thin films via tuning the BixSb1−x layer

Abstract

The intrinsic defects and growth orientation dominate the thermoelectric performance of (Bi_xSb_1−x)₂Te₃ thin films. In this work, a facile method, thermally assisted conversion (TAC), has been employed. All the samples have good crystallization and (0 0 l) growth orientation. Through annealing the precursor layer Bi_xSb_1−x with varying thickness, the Seebeck coefficient and electrical conductivity are decoupled in (Bi_xSb_1−x)₂Te₃. The Seebeck coefficient is dominated by the microstructures. For instance, the annealing-induced pores and thickness-optimized grain boundaries increase the Seebeck coefficient by 21.6% due to the energy filtering. The electrical conductivity is determined by the intrinsic defects. It has to be noted that, with the increase of the film thickness, the charge carrier concentration and Hall mobility increase simultaneously. The resultant electrical conductivity increases by more than 2 times. The highest power factor (PF) of 37.78 μW cm⁻¹ K⁻² is achieved when the annealing temperature is 200 °C and the thickness is 54.2 nm. This work demonstrates that by appropriately tuning Bi_xSb_1−x one can improve the thermoelectric performance of (Bi_xSb_1−x)₂Te₃ effectively, and suggests that TAC is a facile way to synthesize thin films with high crystallization and thermoelectric performance.