High p-type thermoelectric performance driven by a nearly flat band in single-layer CdSbS₃

In this study, using both first-principles calculations and semiclassical Boltzmann transport theory, we have studied the thermoelectric properties of single-layer (1L) CdSbS₃. The first-principles molecular dynamics simulations and phonon dispersion calculations are used to confirm the thermal and dynamic stabilities of 1L-CdSbS₃. In addition, 1L-CdSbS₃ is confirmed to be a semiconductor, displaying indirect bandgaps of 1.238 eV and 2.408 eV obtained from the GGA-PBE and HSE06 functionals, respectively. We also find that 1L-CdSbS₃ exhibits a low lattice thermal conductivity of approximately 4 W m^-1 K^-1 at room temperature. We further show that the p-type Seebeck coefficient, originating from its electronic structure (nearly flat valence band), is higher than those of other two-dimensional thermoelectric materials. Based on the results, 1L-CdSbS₃ achieves a high figure of merit ZT value of up to 1.71 with optimal p-type doping at 450 K. Therefore, this work offers valuable insight into thermoelectric applications and is anticipated to stimulate further theoretical and experimental research.