Tailoring charge carrier dynamics for improved thermoelectric properties in nickel-incorporated Bi₂S₃

Abstract

Bismuth sulphide (Bi₂S₃) is a V-VI group semiconductor, prominent in mid-temperature (303 K–623 K) thermoelectric applications. The performance of n-type bismuth sulfide is limited by its inherently low carrier concentration. Therefore, tuning the carrier concentration is essential prerequisite to achieve high performance. In this work, Bi₂Ni_xS₃ (x = 0, 0.025, 0.050, and 0.075) samples were prepared through a solution-based hydrothermal method followed by the hot-press sintering technique. Herein, transition metal (Ni) introduction significantly enhances the carrier concentration to −8.08 × 10¹⁸ for Bi₂Ni_xS₃ (x = 0.075) samples that reached the highest electrical conductivity of 9835 Sm^-1 at 623 K. The Bi₂Ni_xS₃ (x = 0.025) sample exhibits a remarkably low lattice thermal conductivity value of 0.53 Wm⁻¹K⁻¹ at 623 K, which is due to the enhanced multiple phonon scattering by edge dislocation, twin boundaries, and stacking faults respectively. Consequently, the addition of Ni enhances the transport properties and reduces the intrinsic defects to achieve a combination of high power factor and low-phonon thermal conductivity to obtain a high thermoelectric zT value of 0.16 at 623 K for Bi₂Ni_xS₃ (x = 0.075) sample.