Monolayer Sc2I2S2: An Excellent n-Type Thermoelectric Material with Significant Anisotropy

In recent years, FeOCl-type monolayers regarded as promising thermoelectrics (TE) have attracted a lot of attention. On the basis of first-principles calculations, this work reports excellent TE performance of two-dimensional (2D) Sc2I2S2 with strong anisotropy. At 700 K, 2D Sc2I2S2 exhibits anisotropic lattice thermal conductivities (κl) of 2.41 (x-direction) and 3.33 (y-direction) W/mK. In addition, high and anisotropic n-type PF values were also found in 2D Sc2I2S2, 20.9 (x-direction) and 0.65 (y-direction) mW m–1 K–2. The ZT value of 2.54 is found to be the largest in the x-direction based on n-type doping, which is 7 times higher than in the y-direction (0.35). The big difference in PF and κl reveals the origin of its anisotropy. Our results suggest that FeOCl-type monolayer Sc2I2S2 has excellent TE performance and exhibits strong anisotropy.