FIRST-PRINCIPLES OF ALL-INORGANIC LEAD-FREE HALIDE PEROVSKITES FOR PHOTOVOLTAIC APPLICATIONS
Keywords:
lead-free perovskite, CsSnX₃, density functional theory, PBEsol, WIEN2k, band gap, dielectric function, optical absorptionAbstract
Lead-free inorganic halide perovskites are attractive candidates for photovoltaic and optoelectronic applications because they can combine strong light absorption with tunable electronic structures while avoiding the environmental concerns associated with Pb-containing materials. In this work, first-principles calculations are used to investigate the structural, electronic, and optical properties of cubic CsSnX3 (X = Br, I). The calculations were performed within density functional theory using the full-potential linearized augmented plane-wave approach implemented in the WIEN2k code, with the generalized-gradient-approximation PBEsol functional. Structural optimization was carried out by fitting the total-energy versus volume data with an equation-of-state approach. The calculated equilibrium structural characteristics are consistent with the reported experimental behavior, and substitution of Br by the larger I anion increases the optimized volume and lattice dimensions while reducing the bulk modulus. The calculated band structures show that the valence-band maximum and conduction-band minimum occur at the M symmetry point, indicating direct-gap semiconducting behavior. The calculated gaps are in the visible-energy range, approximately 2.1–2.3 eV, and decrease when Br is replaced by I. Total density-of-states results indicate that the valence region is dominated by Sn-s and halide-p states, whereas Sn-p, halide-p, and Cs-d states contribute strongly to the conduction region. Optical calculations further show finite static dielectric response, pronounced interband transitions, refractive indices near 1.8 at zero photon energy, and strong absorption above the optical threshold. The results indicate that cubic CsSnX3 compounds possess electronic and optical characteristics relevant to visible-light optoelectronic and photovoltaic applications and provide a theoretical basis for further investigation of lead-free tin-halide perovskites.
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Copyright (c) 2025 Tawsif Ahmad, Musa Khan, Moneeb Ahmad, Waqar Ahmad (Author)
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