Tuning thermoelectric power factor of InCoSe thin films through post-annealing engineering
摘要
Thermoelectric (TE) thin films have attracted considerable attention for waste heat recovery owing to their compatibility with microelectronic devices and tunable transport properties. In this work, InCoSe ternary chalcogenide thin films were deposited via thermal evaporation and post-annealed at 650 K for 1–4 h to investigate the influence of annealing duration on their structural, morphological, electrical, and thermoelectric properties. X-ray diffraction revealed progressive improvement in crystallinity up to 3 h of annealing, accompanied by increase in crystallite size from 19.5 to 32.8 nm and reductions in microstrain and dislocation density. Scanning electron microscopy showed enhanced grain growth, improved surface densification, and better grain connectivity after annealing, while prolonged annealing for 4 h resulted in structural deterioration. Hall-effect measurements demonstrated that the carrier concentration, Hall mobility, and electrical conductivity increased with annealing duration up to 3 h owing to reduced defect density and improved carrier transport. The Seebeck coefficient remained positive the entire temperature range (300–500 K), confirming p-type conduction, and reached maximum value of 276.67 μV K⁻1 for the 3-h annealed film at 500 K. The highest electrical conductivity (4.8 × 104 S m⁻1) and power factor (3.67 × 10⁻4 W m⁻1 K⁻2) were obtained for the 3-h annealed sample. The enhanced thermoelectric performance is attributed to the optimized microstructure, improved crystallinity, reduced lattice defects, and enhanced carrier transport achieved through controlled post-annealing. These findings demonstrate that post-annealing engineering is effective approach for tailoring the thermoelectric performance of InCoSe thin films and highlights their potential for medium-temperature thermoelectric energy harvesting applications.