Exploring Thermoelectric Properties Enhancement Through Creation of Defects and Doping

Selenium incorporation provides an effective means of modifying the structural and thermoelectric response of CuS while preserving the characteristic host crystal framework. XRD measurements indicate that the CuS phase remains dominant across the investigated Se concentrations, whereas peak displacement and broadening reveal progressive lattice perturbation. Williamson–Hall analysis shows that the microstrain increases from approximately 4.9 × 10−5 to 8.8 × 10−5 while the crystallite size decreases from about 35.3 to 29.3 nm with increasing Se content. The structural disorder introduced by Se is accompanied by changes in both electronic and thermal transport. The 0.10 Se–CuS composition provides the most favorable overall response, with a Seebeck coefficient of approximately 52 μV K−1, electrical conductivity of 830.6 S cm−1, and power factor of 224.6 μW m−1 K−2 at 300 K. Its thermal conductivity is reduced to approximately 1.85 W m−1 K−1 at 300 K, and the calculated ZT reaches about 0.143 at 500 K. Finite-element simulations further show that the optimized Se–CuS element can sustain a substantial temperature gradient while developing an electrical potential, and the modeled Peltier configuration exhibits a corresponding electrothermal response. The lower performance of the 0.15 composition indicates that excessive dopant-induced disorder can begin to impair charge transport. Overall, the results demonstrate that controlled, rather than maximum, Se incorporation is beneficial for balancing electronic and phononic transport in CuS and provides a useful basis for further development of CuS-based thermoelectric materials.

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