Orthorhombic lead-free hybrid perovskite CH₃NH₃SnI₃ under strain: an ab initio study

We report a computational study where we explore the possibility of tuning the electronic properties of orthorhombic methylammonium tin iodide CH₃NH₃SnI₃ using strains. According to our findings, a moderate [001] strain, smaller than 2%, would open the band gap up to 1.25 eV and enhance the exciton binding energy, opening up new possibilities for the use of CH₃NH₃SnI₃ in technological applications. To better understand the impact of strain, we also examined its influence on bonding properties. The results reveal that the directional pnictogen and the hydrogen bonding are not altered by strains and that the tuning of the electronic properties is the result of changes induced in the orbital contributions to states near the Fermi level and the tilting of the SnI₆ octahedral units.