Strained induced metallic to semiconductor transitions in 2D Ruddlesden Popper perovskites: A GGA + SOC approach.

First principles-based DFT investigation of strain-influenced 2D-monolayer Ruddlesden-Popper (RP) Phenyl-ammonium Tin Iodide (PH 2 SnI 4) perovskite under biaxial strain ranging from ±2%, ±4%, ±6%, to ±8%) was performed. The compressive (-ve) strain caused band gap reduction while tensile strain produced structural elongation with a higher band gap. The competing effects of structural distortion and octahedral tilting offered a band gap tuning, with compressive-strain (Eg 1), zero-strain (Eg 2), and tensile-strain (Eg 3) following the order of Eg 1 < Eg 2 < Eg 3. Unstrained band gap (1.329 eV) gets reduced to 1.262 eV and 1.235, under compressive strain (-ε xx) of −6% and −8%, respectively. However, tensile strains (+ε xx) of +6% and +8% increased the band gap to 1.331 eV and 1.367 eV, respectively. [Display omitted] • A metallic to semiconductor transition is observed under the effect of strain and spin orbit coupling. • All structures are found mechanically stable, with compression offering enhanced stabilization. • Strain induced states are found defects tolerant states contributing to band edges. • Under compressive forces, average bond lengths (Å) and polyhedral volume (Å3) shrink with a higher in-plane tilting of peripheral octahedrons, thus offering a larger bond angle variance (deg.2) of corner octahedrons than the central one. • For compressive-strained configurations, the smaller exciton binding energy corresponds to easily separated electron − hole pairs. • The high absorption coefficient, low reflectivity, and high optical conductivity make these materials suitable for photovoltaic and other optoelectronic device applications. Based on RP perovskites, we put 2%, 4%, 6%, and 8% biaxial strains on 2D monolayers of phenyl-ammonium tin iodide (PH 2 SnI 4) perovskites. Density functional theory (DFT) is used to study the structural distortion, octahedral tilting, band gap tuning, Bader charge analysis, and mechanical stability of the resulting configurations. Band gaps under the effects of compressive strain (Eg1), zero strain (Eg2), and tensile strain (Eg3) follow a decreasing order of Eg 1 (1.262 eV) < Eg 2 (1.329 eV) < Eg 3 (1.331 eV) for 6%-strain. The absence of trap states in energy band gaps and dominant cation and anion contributions at conduction and valence band edges supports the defect tolerance. All the structures analyzed are mechanically stable. The covalently bonded structures are ductile/brittle under tensile/compressive strain, with a prominent stretching mode. Strain improves the optical performance with dielectric constant increased (red-shifted) under compressive strain and reduced (blue-shifted) under compressive strain. [ABSTRACT FROM AUTHOR]