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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 by 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 semi-classical Boltzmann theory. When the zigzag-direction strain is applied, the Seebeck coefficient and electrical conductivity in zigzag direction can be greatly enhanced simultaneously at the critical strain of 5% where the band convergence is achieved. The largest ZT value of 1.65 at 300 K is then achieved 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.