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.