Electronic and Optical Properties of CH₃NH₃SnI₃ and CH(NH₂)₂SnI₃ Perovskite Solar Cell

Using first-principles calculations, a study on the electronic and optical characteristics of perovskite solar cells containing the orthorhombic phases CH₃NH₃SnI₃ and CH(NH₂)₂SnI₃ is conducted. The analysis includes the examination of relaxed geometry structures, electronic band structures, charge density distributions, and van Hove singularities in the density of states to thoroughly examine the orbital hybridizations in chemical bonds. The optical properties of the materials with and without excitonic effects by analyzing dielectric functions, energy loss functions, absorption coefficients, and reflectance spectra are also studied. The findings identify the close connections between the initial and final orbital hybridizations, as well as prominent optical excitations. Based on the computational predictions, It is believed that lead-free materials such as CH₃NH₃SnI₃ and CH(NH₂)₂SnI₃ are promising candidates for photovoltaic applications and are worth experimental testing.