Ultra-low thermal conductivity and high zT in multi-doped AgInSe2: A high-entropy approach to n-type thermoelectric materials

Abstract

The escalating global energy demand and the need for sustainable energy solutions highlight the importance of advancing thermoelectric technologies for efficient waste heat recovery and refrigeration. Although diamond-like chalcogenides are promising high-performance thermoelectric materials, the development of high-efficiency n-type counterparts remains a major challenge. This study introduces a multi-doping approach to synthesize high-entropy diamond-like chalcogenides Ag_xCd_yIn_1-zZn_zSe₂, achieving an ultra-low lattice thermal conductivity of 0.2 W/m.K at 800 K in AgCd_0.2In_0.9Zn_0.1Se₂.This is attributed to the formation of Ag-rich nanoclusters and strong phonon scattering induced by lattice strain and point defects. In parallel, carrier concentration is optimized through excess Ag and multi-doping, which enhances the power factor. As a result, a peak zT of 1.15 at 800 K and an average zT of 0.82 over 370–800 K are achieved, which represents the highest reported values for n-type diamond-like chalcogenides within this temperature range. In addition, a prototype thermoelectric module was fabricated by combining the developed n-type AgCd_0.2In_0.9Zn_0.1Se₂ with p-type Cu_0.8Ag_0.2[Ga_0.8In_0.2]_0.99Zn_0.01Te₂. These results demonstrate the potential of high-entropy diamond-like chalcogenides for next-generation thermoelectric applications while also underscoring the need for further optimization of module integration.