(C₄H₁₀NO)PbX₃ (X = Cl, Br): Design of Two Lead Halide Perovskite Crystals with Moderate Nonlinear Optical Properties

Abstract

Introducing electronegative species into organic constituents was considered to be one effective strategy for adjusting crystal symmetry and designing new nonlinear optical (NLO) materials. By substitution of C4 in piperidine (C 5 H 11 N) with electronegative oxygen, organic morpholine (C 4 H 9 NO) was easily obtained. Therefore, to design NLO crystals, we focused on combinations of stereochemically active lone-pair (SCALP) cation (Pb 2+ )-based chloride and bromide with morpholine molecules. In this work, two lead halide hybrid perovskite (C 4 H 10 NO)PbX 3 (X = Cl, Br, abbreviated as MPbCl 3 and MPbBr 3 , respectively) single crystals with moderate nonlinear optical properties were synthesized by a slow evaporation method. The two title crystals belong to orthorhombic space group P2 1 2 1 2 1 with one-dimensional (1D) chainlike perovskite structures. Theoretical calculations revealed that the second harmonic generation (SHG) responses mainly originate from distorted {PbX 6 } octahedrons of the inorganic framework. Remarkably, moderate phase-matching SHG effects of about 0.70 and 0.81 times KH 2 PO 4 , large birefringences of 0.098 and 0.111 at 1064 nm, and large laser damage thresholds (LDTs) of 19.94 and 46.82 MW/cm 2 were estimated for MPbCl 3 and MPbBr 3 , respectively. This work provides a novel strategy for new purpose-designed hybrid NLO crystals by adjustment and modulation of chemical modification.

Polarizable Anionic Sublattices Can Screen Molecular Dipoles in Noncentrosymmetric Inorganic–Organic Hybrids

“…A recent report by Shen et al offers deeper insight into this phenomenon. Their report on noncentrosymmetric morpholinium lead chloride and bromide systems shows phase-matching SHG effects of 0.70 and 0.81 times KDP, respectively, which would seem to contradict what is seen in the MDA hybrids . However, in contrast to the materials we report, the dipole in their hybrids primarily arises from the acentric coordination environment of the metal halide octahedra.…”

“…Their report on noncentrosymmetric morpholinium lead chloride and bromide systems shows phase-matching SHG effects of 0.70 and 0.81 times KDP, respectively, which would seem to contradict what is seen in the MDA hybrids. 12 However, in contrast to the materials we report, the dipole in their hybrids primarily arises from the acentric coordination environment of the metal halide octahedra. Therefore, while we believe the local electric field on the MDA molecules serves to polarize the charge cloud of the inorganic sublattice to produce a screening effect, the dipole of the morpholinium compounds is actually expected to increase in more polarizable lattices as this allows for greater displacement of lead from the center of its octahedra, in good agreement with their observations.…”

“…While these phases exhibit exceptional photovoltaic performance, their functionality can be largely attributed to the inorganic portion of the hybrid, − with the organic molecules serving primarily as structural building blocks. Attempts to introduce organic moieties with optical properties in the more desirable visible range have demonstrated that the increased size typically required to achieve these properties results in crystal structures with reduced dimensionality in the inorganic connectivity through sheet and chain-like topologies. ,− While the reduced connectivity between the metals and ligands in these phases makes them less attractive for photovoltaic applications, in which high charge-carrier mobility is required, the ability to precisely control the separation between the HOMO and LUMO levels as well as the geometric shape of the molecules offers a promising avenue for tailoring the functionality of these materials. ,− …”

High stability and moderate second-order nonlinear optical properties of hybrid lead-free perovskite [(CH3)3NCH2Cl]CdCl3 bulk crystals

“…Organic-inorganic metal halide perovskites (OIMHPs) have emerged as a new class of functional materials due to their merits of abundant structures and fascinating physical properties, such as optoelectronic, semi-conductive, photoluminescent, ferroelectric, and piezoelectric properties. [1][2][3][4][5][6][7][8] The three-dimensional (3D) structural Pb-based halide perovskites as significant materials of OIMHPs demonstrate excellent performances and have potential applications in optoelectronic fields. 9,10 However, they still endure two main disadvantages, the environmental and biological toxicities of heavy-metal Pb, as well as poor temperature and chemistry stability under exposure to moisture, heat, and light.…”

“…The distorted octahedrons of perovskite functional materials may lead to NCS structures as well as SHG characteristics. 8,13 Thus, it is a great crucial task and academic interest to discover and exploit the NLO performances of perovskite functional materials with NCS structures, especially those with potential applications in solar-blind UV ranges.…”