Ab initio modeling of 2D layered organohalide lead perovskites

Abstract

A number of 2D layered perovskites A2PbI4 and BPbI4, with A and B mono- and divalent ammonium and imidazolium cations, have been modeled with different theoretical methods. The periodic structures have been optimized (both in monoclinic and in triclinic systems, corresponding to eclipsed and staggered arrangements of the inorganic layers) at the DFT level, with hybrid functionals, Gaussian-type orbitals and dispersion energy corrections. With the same methods, the various contributions to the solid stabilization energy have been discussed, separating electrostatic and dispersion energies, organic-organic intralayer interactions and H-bonding effects, when applicable. Then the electronic band gaps have been computed with plane waves, at the DFT level with scalar and full relativistic potentials, and including the correlation energy through the GW approximation. Spin orbit coupling and GW effects have been combined in an additive scheme, validated by comparing the computed gap with well known experimental and theoretical results for a model system. Finally, various contributions to the computed band gaps have been discussed on some of the studied systems, by varying some geometrical parameters and by substituting one cation in another's place.

Excitonic Properties of Chemically Synthesized 2D Organic–Inorganic Hybrid Perovskite Nanosheets

“…Both samples exhibit strong excitonic absorption (≈55%) with an extracted absorption coefficient of ≈1.87 × 10 5 cm −1 at the ground exciton resonance (see Supporting Information for calculation method), which is in accordance with the previously reported values . Similar absorption values of the PEPI and C4PI samples suggest that organic moiety plays a minor role in the ground exciton absorption . From the reflectance and transmittance spectra, we obtained the dielectric function of these two samples as shown in Figure d.…”

Quantum and Dielectric Confinement Effects in Lower-Dimensional Hybrid Perovskite Semiconductors

“…For instance, predictions relevant to the room temperature optoelectronic properties of layered perovskites after systematic DFT structure optimization, 293 must be considered with caution.…”

Combined solid-state NMR, FT-IR and computational studies on layered and porous materials

“…band structures, for 2D and 3D perovskites require a careful consideration of spin-orbit coupling (SOC), 223 and possibly also of long-range Coulombic interactions. 224 These contributions are usually computed within plane waves approaches with non-local density functionals, but a discussion of their possible weight on the simulation of FT-IR or NMR spectra is outside the scope of this work. by Coperet et al 225 They investigated the CO2 chemisorption on colloidal Ba1-xSrxTiO3 nanocrystal surfaces using different techniques, including in situ FT-IR, 13 C ssNMR spectroscopy, and DFT calculations.…”