Anomalous thermoelectric nature in disordered AgSbTe₂-Sb₂Te₃ hetero-phase alloys for room temperature applications

This work focuses on the improvement of the thermoelectric performance of binary antimony telluride (Sb₂Te₃) by co-deposition of silver with antimony telluride. Silver antimony telluride (AgSbTe) thin films are electrodeposited at room temperature by varying Ag concentrations. Silver incorporation in the Sb-Te collapses the crystal structure and turns the films into amorphous AgSbTe₂-Sb₂Te₃ heterostructure. Increased silver in the film increases the Ag (-Te/-O) induced antisite or vacancy defects in the Sb-Te matrix. Addition of silver contributes to the disorder in the heterostructure and increases the density of states near the Fermi level. Valence band analysis confirms that the Fermi level of disordered heterostructure resides within the conduction band minimum, which is responsible for n-type characteristics. This change in electronic states enhances the Seebeck coefficient while decreasing the carrier concentration. An optimum power factor of 236.4 µW m⁻¹ K⁻² is achieved due to the high Seebeck coefficient (-348.45 µVK⁻¹) of the as-deposited ternary film. Thereby, defect-induced structural modification could be an innovative way to enhance the thermometric performance of the materials.