Realizing enhanced thermoelectric properties in Cu2S-alloyed SnSe based composites produced via solution synthesis and sintering

Abstract SnSe emerges as one of the most promising Te-free thermoelectric materials due to its strong anharmonicity and multiple valence bands structure. Recently, compositing has been proven effective in optimizing thermoelectric performance of various metal chalcogenides. Herein, a series of SnSe-xCu2S (x = 0, 0.5%, 1%, 3%, 5%) materials have been fabricated via solution synthesis, particle blending, and spark plasma sintering in sequence. After incorporating Cu2S, the materials become SnSe based composites with Cu doping, S substitution and Cu2SnSe3 secondary phase. We elucidate that the power factor of polycrystalline SnSe can be tuned and enhanced at varied temperature ranges through adjusting the addition amount of Cu2S. Additionally, the composites achieve suppressed lattice thermal conductivity when compared to SnSe itself, as the introduced point defects and SnSe/Cu2SnSe3 interfaces intensify phonon scattering. Consequently, SnSe-0.5%Cu2S and SnSe-3%Cu2S achieve a peak zT of 0.70 at 830 K (intermediate temperature range) and a highly increased zT of 0.28 at 473 K (low temperature range), respectively, which are ∼130% and 200% of values reached by SnSe at the corresponding temperatures. The study demonstrates that our approach, which combines compositing with elemental doping and substitution, is effective in optimizing the thermoelectric performance of SnSe at varied temperature ranges.