Solar cells convert electricity from the solar spectrum to more than 60%. Researchers focused on this promising field because of the most demanding renewable source of electrical energy. Based on the demand, we focused our study on bismuth-doped tin chalcogenide materials for the optoelectronic and solar cell applications. The effect of bismuth concentration on structural, electronic, thermodynamic and optical properties of Sn[Formula: see text]Bi[Formula: see text]Te and Sn[Formula: see text]Bi[Formula: see text]Te materials is studied based on density functional theory (DFT). Generalized gradient approximation (GGA) was proposed to calculate structural parameters, density of states and band structure. Here the lattice parameter increases when increasing bismuth concentration. The parent binary SnTe is in semiconducting behavior with a narrow direct bandgap of 0.234 eV (L-L). From the calculated thermal and optical results, the Gruneisen parameter is maximum for Sn[Formula: see text]Bi[Formula: see text]Te and Debye temperature is maximum for Sn[Formula: see text]Bi[Formula: see text]Te. The studied materials are consistent in IR, visible and UV regions and they are adorable for IR optical detectors and solar cell applications.
By means of Density Functional Theory (DFT) study, we have performed the structural, electronic, optical and thermoelectric properties calculations of tin doped Mg2Si (Mg2Si1−xSnx, x = 0, 0.125, 0.25, 0.5, 0.75, 0.875, 1) using Full Potential Linearized Augmented Plane Wave (FP-LAPW) Method. The DFT study yields satisfactory results for electronic and thermoelectric properties of Sn doped Mg2Si compared with experimental values. With semiclassical Boltzmann transport theory, the transport properties of Mg2Si and Sn doped Mg2Si alloys has been investigated systematically. According to the calculated band structure, density of states and electron density, the parent Mg2Si/Sn materials having indirect energy gap (Γ−x) with ionic bonding; Sn doped ternary combinations Mg2Si1−xSnx, x = 0.125, 0.25, 0.5, 0.75, 0.875 having direct band gap (Γ−Γ) with a mixed covalent and ionic bonding nature. Band gap decreases linearly with the increase of Sn-concentration in each alloy system except for Mg2Si0.75Sn0.25 combination. The optical properties calculations have been performed for the energy range between 0–13.5 eV. The thermoelectric properties have been calculated for the temperature range 100 K to 800 K. Out of the five studied materials, Mg2Si0.75Sn0.25 found to be a better thermoelectric material with increased Power factor, Seebeck coefficient, electrical conductivity and corresponding thermal conductivity at high temperature range.
Lead-free SnTe compound is an alternative material for thermoelectric devices offering suitable band gap, non-toxicity, and mechanical stability. Here the structural, electronic, mechanical, thermal, thermoelectric, and optical properties of parent binary SnTe and ternary SnTe0.125Se0.875, SnTe0.25Se0.75, SnTe0.5Se0.5, SnTe0.75Se0.25, SnTe0.875Se0.125 materials are discussed at ambient conditions using full-potential linearized augmented plane wave method based on density functional theory. To make an accurate band gap we have used the mBJ scheme for the parent compound. The stability of the materials was confirmed using their calculated elastic constants. From the calculated mechanical properties, we have noted that the SnTe0.25Se0.75 material is more ductile and the SnTe0.875Se0.125 material has more hardness and a more brittle nature compared to other materials. We have computed the Seebeck coefficient, electrical conductivity, and power factor value in the temperature range of 300 to 1000 K in steps of 100 K using Boltzmann transport theory interfaced with the Wien2k program. From the thermoelectric properties, the ternary SnTe0.5Se0.5 havs a high power factor due to maximum electrical conductivity and is identified as a potential compound for thermoelectric applications. From the calculated optical results, the series of SnTe combinations are deemed suitable materials for optoelectronic applications. Our theoretical results are agreed well with available experimental results.
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