Pressure induced thermoelectric enhancement in SnSe crystals

SnSe crystals are excellent thermoelectric materials due to their high ZT value (∼2.6 along the b direction) at high temperature ∼923 K. However, in the temperature range of 300-773 K, the ZT values are just 0.1-0.9. To make this material more efficient, its thermoelectric properties should be large in the entire temperature range. Here, we use computational methods to show how pressure intrinsically enhances the thermoelectric properties below 700 K along the three directions (a, b and c) of the crystal (the low-T SnSe-Pnma phase) due to the significant electrical transport boost. The estimated ZT values of p-type materials along the b and c directions can reach as high as 2.5 and 1.7 at 6 GPa and 700 K, respectively. At 6 GPa, the a direction shows potential n-type behavior with a ZT value of 1.7 at 600 K. It is significant that high performance for both n-type and p-type conductors could be available in SnSe just through applying pressure. Our work on SnSe under pressure sheds light on a new mechanism to enhance the thermoelectric properties of materials.