Thermal and thermoelectric properties of monolayer indium triphosphide (InP3): a first-principles study

Monolayer indium triphosphide (InP3) is a newly predicted 2D material with a quasi-direct electronic band gap which is predicted to exhibit fascinating adsorption efficiency, foreshadowing its potential applications in the photovoltaic and optoelectronic communities. To achieve a combination of photovoltaic and thermoelectric technologies and further boost the energy utilization rate, in this paper we systematically investigate the thermal and thermoelectric properties through combining first-principles calculations and semiclassical Boltzmann transport theory. Our calculations show that the average lattice thermal conductivity of monolayer InP3 is about 0.63W mK(-1) at room temperature, which is comparable to that of classical thermoelectric materials. Such a poor phonon transport property mainly originates from its smaller group velocity and stronger phonon-phonon scattering (including both scattering magnitude and channels). Unlike the isotopic phonon transport property, the electronic conductivity and electronic thermal conductivity of monolayer InP3 present obvious anisotropic behavior. Meanwhile, a high Seebeck coefficient is also predicted in monolayer InP3 with both n- and p-type doping due to the large electronic band gap and sharp increase in electronic conductivity. By using the electron relaxation time estimated from deformation potential theory, the room temperature thermoelectric figure of merit of monolayer InP3 is found to be as high as 2.06 (with p-type doping) and 0.61 (with n-type doping) along the armchair and zigzag directions, which are substantially larger than for black phosphorene (ZT similar to 0.4 at room temperature). The results presented in this work shed light on the thermoelectric performance of monolayer InP3 and qualify its potential application in a multifunction device that contains both photovoltaic and thermoelectric technologies.