Structural, electronic, and optical study of lead-free perovskite CH3NH3SnBr3 under compressive strain using DFT and DFT plus U

Due to their outstanding efficiency and optoelectronic properties, organic-inorganic lead halide perovskites have attracted considerable interest as light absorbers in photovoltaic cells. However, the presence of toxic lead in the plurality of hybrid perovskites has negative environmental repercussions. This study focused on the structural, electronic, and optical properties of a lead-free organic-inorganic perovskite CH3NH3SnBr3 under different compressive strains. An analysis of results obtained using density-functional theory (DFT) and DFT + U indicated high agreement between the results achieved using the DFT + U with the spin -orbit coupling (SOC) approach and the experimental results. The electronic properties obtained using DFT + U with SOC demonstrated that an increase in compressive strain led to variations in the bandgap in an oscillatory manner, passing through decreasing, increasing, and decreasing phases. Moreover, the optical property results revealed an increase in the static dielectric constant as a function of increasing compressive strain. Furthermore, all structures of the CH3NH3SnBr3 perovskite exhibited high absorption coefficients (approximately 105 cm-1) in the ultraviolet and visible regions, with a shift towards lower energies of the spectrum when the compressive strain increased. Our results could encourage experimenters to develop lead-free materials by considering external factors (e.g., compressive strain) for applications in optoelectronics.