Strain-tuned structural, optoelectronic and dielectric properties of cubic MAPbI3 perovskite driven by SOC using first-principles theory

In this report, we used first-principles density functional theory calculations to investigate the effect of compressive and tensile strains ranging from −6% to +6 % on the consideration of structural, optical, and electronic properties of CH₃NH₃PbI₃ (Methylammonium lead triiodide, hereafter MAPbI₃) perovskite. At the R-point of electronic band structures, the unstrained planar CH₃NH₃PbI₃ molecule exhibited a direct electronic bandgap of 1.6744 eV and 0.5187 eV without and with spin-orbit coupling (SOC) effect, respectively. Due to the SOC effect, the bandgap of CH₃NH₃PbI₃ perovskite increased as the tensile strains rose. On the contrary, the bandgap decreases with increasing compressive strains. The density of states (DOS) and projected density of states (PDOS)/total density of states (TDOS) described that the valence bands and the conduction bands of MAPbI₃ perovskite are controlled by I-p orbitals and Pb-p orbitals, respectively. The CH₃NH₃PbI₃ perovskite also has strong absorption capabilities in the photon energy region of 2 eV–2.75 eV, as evidenced by the optical studies. The main peak of the dielectric function shifts toward the lower photon energies with increasing compressive strains (redshift effect). However, the dielectric function peaks were blue-shifted by incorporating the tensile strains. The study exposed that SOC significantly modifies the electronic band structure, leading to modifications in phenomena of the perovskite structure. Furthermore, SOC-induced changes in the dielectric response highlight its role in shaping the material's characteristics. This comprehensive investigation provided fundamental insights into the potential manipulation of MAPbI₃ perovskite for enhanced device performance in photovoltaic and optoelectronic applications.