Exploring a Novel Atomic Layer with Extremely Low Lattice Thermal Conductivity: ZnPSe ₃ and Its Thermoelectrics

We survey the thermodynamic stabilities and properties, electronic transports, and thermoelectric possibilities of two-dimensional (2D) ZnPS ₃ and ZnPSe ₃ , belonging to transition-metal phosphorus trichalcogenides, by employing the first-principles electronic structure calculation. Our first-principles calculation accompanying ab initio molecular dynamics and phonon calculation predicts that a single-layer (1L-) ZnPSe ₃ would be thermodynamically stable; in addition, electron and hole mobilities of 1L-ZnPSe ₃ amount to ∼440 and ∼400 cm ² V ^-1 s ^-1 , respectively, which are comparable to 1L-MoS ₂ . More interestingly, the lattice thermal conductivity of 1L-ZnPSe ₃ is found to be lower than any other 2D material, which could reach the lowest, i.e., ∼0.13 W m ^-1 K ^-1 at room temperature. In contrast, the thermoelectric figure of merit of the pristine 1L-ZnPSe ₃ is just ∼0.8 under optimal condition. Nevertheless, this is a very promising indication for a thermoelectric application of 1L-ZnPSe ₃ because other elements to determine the thermoelectric figure of merit could be possibly engineered through a manipulation of underlying electronic structures. With this finding, 1L-ZnPSe ₃ would be added as a novel promising candidate to a list of 2D thermoelectric materials.