Synergistic effect of CuInSe2 alloying on enhancing the thermoelectric performance of Cu2SnSe3 compounds

Abstract

Cu₂SnSe₃ based compounds with a diamond-like structure are promising thermoelectric materials. However, the relatively high lattice thermal conductivity limits further improvement in their thermoelectric performance. In this work, two compounds including In₂Se₃ and CuInSe₂ are employed to alloy with Cu₂SnSe₃ aiming to decrease lattice thermal conductivity and their corresponding effects are compared. It is found that alloying with CuInSe₂ is more beneficial to reduce lattice thermal conductivity and maintain the power factor, as evidenced by a higher quality factor B. Subsequently, both In and Ga doping is performed to regulate the carrier concentration of (Cu₂SnSe₃)_0.80(CuInSe₂)_0.2. Finally, (Cu₂Sn_0.97Ga_0.03Se₃)_0.80(CuInSe₂)_0.20 displays a decent zT of ∼0.98 at 823 K, a nearly six-fold higher value compared to that of the pristine sample. Additionally, a zT_ave of ∼0.35 over 300–823 K is obtained in (Cu₂Sn_0.97Ga_0.03Se₃)_0.80(CuInSe₂)_0.20, which is among the best reported p-type Cu₂SnSe₃ based compounds. The result proves that alloying with CuInSe₂ combined with carrier concentration optimization is a valid strategy to improve the thermoelectric performance of Cu₂SnSe₃ based compounds.