Promising thermoelectric candidate based on a CaAs₃ monolayer: A first principles study

The CaAs₃ monolayer is a newly predicted two-dimensional material with attractive properties, such as a moderate direct bandgap, high carrier mobility, prominent visible-light absorption, etc. To evaluate its potential applications in thermoelectric (TE) fields, herein, the thermoelectric properties of CaAs₃ monolayers were comprehensively investigated by a first-principles method in combination with Boltzmann transport theory. Our calculated results indicate that the CaAs₃ monolayer has an exceptionally low lattice thermal conductivity of 0.44 W m^-1 K^-1 at 300 K, mainly because of the small group velocity and strong phonon-phonon scattering. The CaAs₃ monolayer also exhibits a high power factor due to the large Seebeck coefficient and electrical conductivity. Therefore, large ZT values of 1.72/1.58 were achieved for the n-type/p-type CaAs₃ monolayer at 800 K. Compared with conventional 2D TE materials, the CaAs₃ monolayer does not contain expensive heavy elements, which is beneficial for its practical applications as a TE material. Our results qualify the CaAs₃ monolayer as a promising candidate for building excellent 2D TE devices.