Electronic structure and thermoelectric properties of uniaxial strained SnSe from first-principles calculations

Abstract

SnSe is a promising candidate of thermoelectric material for its high ZT value. To further optimize its thermoelectric performance, we systematically investigate the uniaxial strain dependence of electronic structure and thermoelectric properties for both p- and n-type SnSe based on first-principles calculations and Boltzmann transport equation. The band gap of SnSe can be significantly tuned by the uniaxial strain along b-axis. The momentum alignment and energy convergence of band structure induced by uniaxial strains are observed. The Seebeck coefficient, electrical conductivity and power factor can be significantly improved by applying suitable uniaxial strains. In particular, for p-type SnSe at 300 K, the peak value of PFxx/τ for εa = −6% is 7.6 times as large as that of unstrained SnSe. The peak values of PFxx/τ, PFyy/τ and PFzz/τ in p-type SnSe at 300 K under εb = −6% are 2.6, 2.0 and 2.3 times as large as those of unstrained SnSe, respectively. At 750 K, the peak value of PFzz/τ increases by 96.9% under εc = −6% in p-type SnSe and the peak value of PFyy/τ increases by 73.2% under εb = 6% in n-type SnSe. Our findings indicate that uniaxial strain can be an efficient strategy to modulate the thermoelectric properties of SnSe and provide a helpful perspective for its practical applications.