Enhanced thermoelectric performance of phosphorene by strain-induced band convergence

The newly emerging monolayer phosphorene was recently predicted to be a promising thermoelectric material. In this work, we propose to further enhance the thermoelectric performance of phosphorene using the strain-induced band convergence. The effect of the uniaxial strain on the thermoelectric properties of phosphorene was investigated by using the first-principles calculations combined with the semiclassical Boltzmann theory. When the zigzag-direction strain is applied, the Seebeck coefficient and electrical conductivity in the zigzag direction can simultaneously be greatly enhanced at the critical strain of 5%, at which the band convergence is achieved. The largest $ZT$ value of 1.65 at 300 K is then conservatively estimated by using the bulk lattice thermal conductivity. When the armchair-direction strain of 8% is applied, the room-temperature $ZT$ value can reach 2.12 in the armchair direction of phosphorene. Our results indicate that strain-induced band convergence could be an effective method to enhance the thermoelectric performance of phosphorene.