Mixed Organic Cation in Chiral Two-Dimensional Organic-Inorganic Hybrid Metal Halides: An ab-initio Study of Nonlinear Optical (NLO) Properties

TL;DR

This study uses ab-initio calculations to explore how mixing organic cations affects the structure and nonlinear optical properties of chiral 2D hybrid metal halides, revealing potential for NLO applications.

Contribution

It provides the first detailed ab-initio analysis of mixed organic cation chiral hybrid metal halides and their nonlinear optical responses.

Findings

Wide bandgaps (~3.5 eV) observed in compounds.

Strong second harmonic generation responses (~0.5-1.5*KDP).

Moderate birefringence (~0.088).

Abstract

The mixing of organic cations represents yet another direction to explore in the field of chiral organic-inorganic hybrid metal halides (OIHMH). Here, we perform structural optimizations, electronic structures, and non-linear optical (NLO) studies using the density functional theory of two recently synthesized chiral OIHMHs, [R-MePEA][C3A]PbBr4, and [R-MePEA][C4A]PbBr4, with mixed chiral arylammonium and achiral alkylammonium cations. We find that the noncovalent weak interactions (e.g. Br...NH interactions) play an important role in the formation of these OIHMHs. Our study further indicates that the two non-centrosymmetric compounds exhibit relative wide bandgaps (~3.5 eV), strong second harmonic generation (SHG) responses (~0.5-1.5*KDP), and moderate birefringence (~0.088), indicating possible applications NLO materials. Atom response theory analysis reveals that the SHG responses are determined mainly by the occupied Br 3p non-bonding orbitals as well as by the unoccupied Pb 5p orbitals which shows the important contribution of the inorganic PbBr4 layer to the nonlinear optical properties.