Toward Ultrahigh Thermoelectric Performance of Cu 2 SnS 3 -Based Materials by Analog Alloying.

Cu 2 SnS 3 is a promising thermoelectric candidate for power generation at medium temperature due to its low-cost and environmental-benign features. However, the high electrical resistivity due to low hole concentration severely restricts its final thermoelectric performance. Here, analog alloying with CuInSe 2 is first adopted to optimize the electrical resistivity by promoting the formation of Sn vacancies and the precipitation of In, and optimize lattice thermal conductivity through the formation of stacking faults and nanotwins. Such analog alloying enables a greatly enhanced power factor of 8.03 µW cm -1 K -2 and a largely reduced lattice thermal conductivity of 0.38 W m -1  K -1 for Cu 2 SnS 3 - 9 mol.% CuInSe 2 . Eventually, a peak ZT as high as 1.14 at 773 K is achieved for Cu 2 SnS 3 - 9 mol.% CuInSe 2 , which is one of the highest ZT among the researches on Cu 2 SnS 3 -based thermoelectric materials. The work implies analog alloying with CuInSe 2 is a very effective route to unleash superior thermoelectric performance of Cu 2 SnS 3 .