Ultra-low thermal conductivity and high thermoelectric performance of two-dimensional triphosphides (InP3, GaP3, SbP3 and SnP3): A comprehensive first-principles study
By performing first-principles calculations combined with Boltzmann transport equation, we report a comprehensive study for the thermal and thermoelectric properties of monolayer triphosphides, that is, InP3, GaP3, SbP3 and SnP3. Firstly, we studied the structure, phonon dispersion and discussed the long-range atomic interactions by analyzing second-order interatomic force constants (IFCs). Next, we predicted the corresponding thermal conductivities of the monolayer InP3, GaP3, SbP3 and SnP3 at 300 K to be 0.64 W/mK, 3.02 W/mK, 1.04 W/mK and 0.48 W/mK, respectively. To acquire thermoelectric properties, the carrier mobility and electron relaxation time of the four materials were predicted by the deformation potential theory method and explained by analyzing energy band structures. Then, the Seebeck coefficient, electrical conductivity and thermoelectric figure of merit (ZT) at different temperatures were calculated through the Boltzmann transport equation with relaxation time approximation. At last, we predicted that the maximum ZT values of InP3, GaP3, SbP3 and SnP3 are evaluated up to 2.6, 0.9, 1.9 and 3.7 at 300 K and up to 4.6, 1.6, 3.5 and 6.1 at 500 K, respectively. With ultra-low thermal conductivity and high thermoelectric performance, monolayer triphosphides are considered as the potential candidates for thermoelectric materials.