Effect of concentration of electrolyte on thermoelectric properties of electrodeposited Bi₂Te₃ thin films

The current thread of study focuses on tuning the properties of nanostructured Bi₂Te₃ films for thermoelectric applications, by optimizing electrodeposition conditions, such as the deposition potential, pH of the electrolyte, temperature, and concentration of the precursors in the solvent. In this paper, small coagulated masses of Bi₂Te₃ dendritic nanostructures were electrodeposited on a stainless-steel substrate for six different concentrations of Bi³⁺ ions in the electrolyte (varied from 2.5 to 15 mM) at previously optimized deposition potential and pH conditions. Systematic testing of electrodeposited films has been carried out to analyze the effect of variation of Bi³⁺ ions. Cyclic voltammetry studies revealed irreversible electrodeposition of Bi₂Te₃ films. A series of scanning electron micrographs revealed the evolution of small coagulated masses of dendritic nanostructures. Thermoelectric properties such as a Seebeck coefficient up to -45.81 μV/K and power factor up to 311 μW/cmK² have been achieved for the deposited films. The results reveal significant variation in the thermoelectric properties as a function of the concentration of Bi³⁺ in the electrolyte through changes in the surface morphology and stoichiometry of the films. The analysis also revealed ideal concentrations of precursor ions to obtain Bi₂Te₃ as the dominant phase.