<p>This study presents enhanced thermoelectric performance in 4% Sb-doped CuInS₂ thin films through optimized annealing. The films were deposited using thermal evaporation method at ambient temperature, 373, and 473 K, followed by characterization employing the photothermal deflection (PTD) technique. Increasing the annealing temperature to 473 K led to significant improvements in electrical conductivity (from 4.5 to 13.9 S&#xa0;cm⁻¹) and thermal conductivity (reaching 0.075 W m⁻¹&#xa0;K⁻¹), alongside a reduction in thermal diffusivity (to 0.65 10^–6&#xa0;m²&#xa0;s⁻¹). These enhancements are attributed to improved crystallinity, reduced grain boundary scattering, and optimized carrier dynamics. The thin films exhibited an estimated Seebeck coefficient of + 52 µV K⁻¹ (p-type) and achieved a figure of merit (zT) of 0.015 at 300 K. Notably, a substantial reduction in thermal conductivity was observed compared to undoped CuInS₂, accompanied by an improvement in zT. The work establishes low-temperature annealing (≤ 473 K) as a scalable and effective strategy for developing high-performance thermoelectric materials in flexible applications.</p>