The substitution of lead (Pb) with tin (Sn) at the B-site of halide perovskites offers a compelling approach toward the development of non-toxic, environmentally sustainable optoelectronic materials. In this work, first-principles Density Functional Theory (DFT) calculations are used to examine the structural, electronic, and optical characteristics of CsPbBr3 and CsSnBr3. Structural optimization reveals that both materials stabilize in a cubic Pm 3m (#221) symmetry with a tolerance factor of 0. 83 and 0. 88, underscoring their structural robustness. Remarkably, substituting Pb with Sn leads to a significant reduction in the band gap, from 2. 80 eV in CsPbBr3 to 1. 42 eV in CsSnBr3 (calculated using the TB-mBJ method), transitioning these materials toward better suitability for visible-light absorption. The optical properties reveals that CsSnBr3 exhibits a higher static dielectric constant and refractive index than CsPbBr3, with comparable absorption onset near 0. 63 eV. These results reveal the CsSnBr3 potential for effective optoelectronic applications by providing increased light-matter interaction and enhanced dielectric screening. In this study, the role of B-site cation substitution in tuning key material properties, this work provides critical insights for the design of lead-free, sustainable perovskites, offering a promising pathway toward environmentally friendly technologies that address the growing demand for clean energy.
Choudhary et al. (Thu,) studied this question.