First-principles calculations to investigate thermoelectric efficiency of β-In2S3 under pressure for renewable energy sources

The effect of hydrostatic pressure and temperature on thermoelectric properties of Indium sulfide (β-In2S3) in the tetragonal crystal structure is studied using the first principal calculations and the full potential-linearized augmented plane wave (FP-LAPW) method. The Pedrew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA), local density approximation (LDA) and Tran and Blaha modified Becke-Johnson (TB-mBJ) potential are used for calculation of exchange–correlation potentials. Calculated indirect bandgaps are 0.95, 1.17, and 2.19 eV by LDA, PBE-GGA, and TB- mBJ approximations. Obtained bandgap by TB-mBJ approximation is in good agreement with the experimental result. Calculated density of state spectra show the p orbital of S atoms have significant contribution near the Fermi level. The thermoelectric properties of β-In2S3 under pressure like the Seebeck coefficient SC, the electronic thermal conductivity κe, the electrical conductivity σ, the figure of merit ZT, the electronic specific heat CT,μ and Pauli magnetic susceptibility χT,μ are also calculated. As a result, ZTmax of 0.48 (at 500 K) and 0.41 (at 300 K) are obtained for β-In2S3 at zero pressure. The value of SC for p-type carrier was higher than that of n-type one for β-In2S3. By increasing temperature, electronic thermal conductivity increases but there is no change in electrical conductivity and it remains constant at all temperatures. The maximum values of electronic specific heat and Pauli magnetic susceptibility at zero pressure and room temperature are calculated about 17.168 (J/mol K) and 10.3 × 10−9 (m3/mol), respectively. The electronic specific heat increases with increasing temperature. According to the Curie-Weiss law, the Pauli magnetic susceptibility decrease with increasing temperature. Due to the low lattice thermal conductivity, suitable figure of merit ZT and wide band gap of β-In2S3 have possibilities of applications in the thermoelectric renewable energy sources and solar cells devices.