Abstract
The crystal structure,mechanical stability,phonon dispersion,electronic transport properties and thermoelectric(TE)perfor-mance of the Bi2Sn2Te6 monolayer are assessed with the first-principles calculations and the Boltzmann transport theory.The Bi2Sn2Te6 monolayer is an indirect semiconductor with a band gap of 0.91 eV using the Heyd-Scuseria-Ernzerhof(HSE06)functional in consideration of the spin-orbit coupling(SOC)effect.The Bi2Sn2Te6 monolayer is high thermodynamically and mechanically stable by the assessments of elastic modulus,phonon dispersion curves,and ab initio molecular dynamics(AIMD)simulations.The hybrid bonding characteristics are discovered in Bi2Sn2Te6 monolayer,which is advantageous for phonon scattering.The antibonding interactions near the Fermi level weaken the chemical bonding and reduce the phonon vibrational frequency.Due to the short phonon relaxation time,strong anharmonic scattering,large Grüneisen parameter,and small phonon group velocity,an ultralow lattice thermal conductivity(0.27 W/(m·K)@300 K)is achieved for the Bi2Sn2Te6 monolayer.The optimal dimensionless figure of merit(ZT)values for the n-type and p-type Bi2Sn2Te6 monolayers are 2.68 and 1.63 at 700 K,respectively,associated with a high TE conversion efficiency of 20.01％at the same temperature.Therefore,the Bi2Sn2Te6 monolayer emerges as a promising candidate for TE material with high conversion efficiency.
万方数据