High Thermoelectric Performance in n-doped Silicon-Based Chalcogenide Si₂Te₃

Silicon-based thermoelectric materials would be of great significance due to the huge dependence of electronic industry on silicon. Bulk silicon is not a good thermoelectric material due to its very high thermal conductivity, thereby limiting its thermoelectric efficiency. Nanostructuring and alloying are alternative solutions to reduce thermal conductivity, but the techniques involved are complex and costly. Recently, a silicon-based chalcogenide Si₂Te₃ has been experimentally synthesized. Si₂Te₃ exhibits layered structure, in which Te atoms form hexagonal sub-lattice and Si atoms can occupy any of the octahedral voids. Due to uncertainty in Si positions, previously unknown ground state structure of Si₂Te₃ was obtained using the Wyckoff positions of space group P-31c. The minimum energy configuration exhibits combination of desirable electronic and transport properties. In particular, n-doped Si₂Te₃ has an unprecedented figure of merit of 1.86 at 1000 K, which is comparable to some of the best state-of-the-art thermoelectric materials. Hence, n-doped Si₂Te₃ can be a long-sought silicon-based thermoelectric material which could be integrated to the existing electronic devices.
Reference: R. Juneja, T. Pandey, and A. K. Singh, Chem. Mater. 29, 3723-3730, 2017