Strain engineering on the thermoelectric performance of monolayer AlP₃: A first-principles study

Recently, the two-dimensional semiconductor AlP₃ has been proved to be a promising thermoelectric material with high carrier mobility and low thermal conductivity. By using first-principles methods combined with Boltzmann transport theory, we investigate the effect of biaxial tensile strain on the thermoelectric properties of monolayer AlP₃. Through calculating electronic transport properties, we find that the electron mobility first increases and then drops with the increase of tensile strain. Furthermore, the power factor of monolayer AlP₃ under a 4% tensile strain has been significantly improved, indicating that strain engineering could enhance the power factor of monolayer AlP₃. Moreover, the tensile strain will increase the electronic and lattice thermal conductivities. Compared with unstrained AlP₃, the increase of lattice thermal conductivities of strained monolayer AlP₃ results from a higher phonon lifetime. The ZT and maximum energy conversion efficiency of n-type doping monolayer AlP₃ under a 4% tensile strain can reach 7.13 and 29.4% at 700 K. This study provides an in-depth understanding of the transport properties of monolayer AlP₃ by applying tensile strain and monolayer AlP₃ has a great potential in flexible thermoelectric applications.