Research progress on polycrystalline SnSe-based thermoelectric materials

Abstract

Single-crystal SnSe exhibits outstanding thermoelectric performance; however, its poor mechanical properties, high preparation cost, and limited scalability have hindered its practical application. In contrast, polycrystalline SnSe, which combines intrinsically low lattice thermal conductivity derived from its layered structure, tunable carrier transport characteristics, and superior processability and industrial potential, has emerged as an important research focus in the field of mid-temperature thermoelectric energy conversion. This review systematically summarizes the research progress in polycrystalline SnSe thermoelectric materials over the past five years, with particular emphasis on their fundamental characteristics, preparation process optimization, doping regulation, non-composite structural engineering, and composite/heterointerface engineering. Available studies show that, through the synergistic regulation of coupled electrical and thermal transport via grain-boundary chemistry control, oxide removal, multiscale defect engineering, band-structure modulation, and functional interface design, the thermoelectric performance of polycrystalline SnSe has been markedly improved from its initially modest level. In some systems, the ZT value has exceeded 3.0, demonstrating promising application potential. Meanwhile, current research has shifted from the sole pursuit of peak ZT toward the comprehensive optimization of broad-temperature-range performance, composite design, structural reliability, and device applicability. Finally, this review summarizes the key challenges that remain in polycrystalline SnSe, including doping mechanisms, interface effects, long-term thermal stability, and scalable reproducible fabrication, and provides an outlook on future development directions, with the aim of offering guidance for the design and application of high-performance SnSe-based thermoelectric materials.