Strain enhanced thermoelectric performance of Lu2CF2 MXene

Abstract

The thermoelectric performance of Lu${}_2$CF${}_2$ MXene monolayer under biaxial tensile strain is explored using the first-principles method and Boltzmann transport theory. Biaxial strain enhances the electron–phonon relaxation time, leading to elevated electrical conductivity and increasing the thermoelectric power factor (PF). Specifically, the PF of n-type Lu${}_2$CF${}_2$ rises from 4.6 mW/mK² to 13.7 mW/mK² when subjected to a 4% biaxial tensile strain at 700 K, showing an almost threefold increase. Similarly, for p-type, the PF increases to 8.2 mW/mK² from 3.9 mW/mK², which is more than double. The modulation of lattice thermal conductivity (${\kappa }_l$) also occurs under tensile strain conditions. The ${\kappa }_l$ at 300 K, also decreases to 16.2 Wm⁻¹K⁻¹ from 88 Wm⁻¹K⁻¹ under 6% tensile strain, indicating an approximately 81.5% reduction. The combination of higher PF and lower ${\kappa }_l$ results in a significant enhancement in the thermoelectric figure of merit (ZT), increasing it from 0.07 to 0.68 for n-type and from 0.06 to 0.63 for p-type at 700 K. The ZT sees an almost tenfold increase compared to the strain-free scenario, indicating that biaxial tensile strain can effectively enhance the thermoelectric efficiency of the monolayer of Lu${}_2$CF${}_2$.