Extraordinary thermoelectric performance in 2D group III monolayer XP3 (X = Al, Ga, and In)

Recently, two-dimensional (2D) group III monolayer XP3 (X = Al, Ga, and In) have attracted great attention due to their excellent physical properties. We systematically investigate the thermoelectric (TE) properties of monolayer XP3 by combining first-principles calculations and Boltzmann transport theory. It can be confirmed that monolayer XP3 are dynamically stable structures and semiconductors with indirect band gaps. The carrier mobilities of monolayer XP3 are calculated by using the deformation potential theory. Besides, at 300 K, the power factors of n-type doping AlP3, GaP3, and InP3 are 35.51, 12.47, and 18.41 mW m−1 K−2, respectively. Moreover, the phononic transport properties of all monolayers are evaluated, and lattice thermal conductivities of AlP3, GaP3, and InP3 are 0.60, 4.47, and 1.93 W m−1 K−1 at 300 K, respectively, which can be explained by small phonon group velocity and ultra-low phonon lifetime. Finally, the outstanding TE figure of merits (ZT) of AlP3, GaP3, and InP3 with n-type doping are 8.33, 2.09, and 4.22 at 700 K, respectively, which establishes a new record of TE performance of 2D materials. Our work clearly shows the prominent properties of novel 2D material XP3 and will further promote technological development in the TE field.