Band gap tailoring with octahedral distortion and bader charge analysis for 2D-Ruddlesden-Popper monolayer tin halide perovskites

Intercalation of large organic spacer cations with inorganic layers of octahedral metal halide cages in 2D-Rud-dlesden-Popper (RP) monolayer perovskites (R-NH3)2An-1BnX3n+1 by using a rational design approach has shown structural versatility and energetic stability. A systematic theoretical investigation of the structural, electronic, and mechanical properties was conducted with and without spin-orbit coupling (SOC) under the influence of a range of organic monovalent spacer cations [R-NH3]+ with different inorganic halide anions. This resulted in 12 compositions. Lattice distortion and octahedral tilting provided gradient band gaps that displayed a good linear relationship with equatorial Sn-X-Sn angles in debt of larger halide anions. By fixing halide ions, larger spacer cations reduce the band gap further. The halides function as acceptors, whereas Sn and N function as donors. Intermingled N-atoms of spacer cations incorporate additional charges to axial halide ions of [SnX6]4-with state-of-the-art features of defect tolerance, quantum and dielectric confinement, low effective masses, and high mobility.