Strain effects on the electronic and thermoelectric properties of Bi2Te3: A first principles study

In the present work, the effect of biaxial mechanical strains (pressure and tensile) on the structural, electrical and thermoelectrically properties of bismuth telluride (Bi2Te3) has been studied. Using the first principles calculation through Generalized Gradient Approximation (GGA without spin-orbit), and Boltzmann transport theory, the band structure, density of state, Seebeck coefficient, electrical and thermal conductivities have been investigated. Our results indicate that Bi2Te3 band gap without spin orbit is direct about 0.3 eV. In evaluating a series of mechanical strain values ranging from [-3%-3%], under pressure the band gap increases up to 0.6 eV, while the Seebeck coefficient, the thermal and the electrical conductivities decrease. However, under tensile strain, an opposite behavior is observed, which summarize a sharp decrease in the Seebeck coefficient at 3% accompanied by the overlapping valance and conduction bands. These results of anomalies in the electronic structure produce a change in the transport properties. Finally, the pressure effect is able to improve the thermoelectric properties, which positively enhance the factor of merit ZT.