Optimization of annealing conditions to enhance thermoelectric performance of electrodeposited p-type BiSbTe thin films

In this work, we report the optimization of annealing process to improve the thermoelectric properties of pulse electrodeposited bismuth antimony telluride (Bi-Sb-Te) films by varying the annealing time-temperature profile. The innovative approach of sandwiched Te in between the Bi-Sb-Te layers aids in compensating the loss of tellurium during the annealing of BiSbTe thin films. An optimized Seebeck coefficient of 90.5 μV/K along with a power factor of 240 μW/mK² is achieved for samples annealed at 350 °C for 1 h under N₂ atmosphere with controlled heating and cooling rates. These improvements are attributed to a significant decrease in the carrier concentration as substantiated by the Hall measurements and to the increase in the crystallite size at the elevated temperatures as indicated by the X-ray diffraction pattern data. A comprehensive study on the annealing parameters reveals that the Seebeck coefficient and the electrical conductivity are considerably more sensitive to the annealing temperature than compared to the annealing time.