• • InBr3 doping elevates carrier mobility to ~20.64 cm2 V−1 s−1 in n-type polycrystalline SnSe, a critical improvement for electrical conductivity and power factor.
• • Lattice thermal conductivity is suppressed to ~0.25 W m−1 K−1 via multi-scale defects (dislocations and Br-rich nanowires), enhancing phonon scattering and thermal insulation.
• • A peak ZT of ~1.41 at 823 K is achieved, representing a significant advancement for medium-temperature thermoelectric applications.
• • An average ZT of ~0.42 over 323–823 K indicates stable performance across a wide temperature range, essential for practical device operation.