Three-Dimensional Perovskite Methylhydrazinium Lead Chloride with Two Polar Phases and Unusual Second-Harmonic Generation Bistability above Room Temperature

Abstract

Formation of noncentrosymmetric three-dimensional (3D) lead halide perovskites has been a widely sought after goal because the polar structure opens up new vistas to properties of these materials, e.g., improved charge separation for photovoltaics arising from ferroelectric order. Here, we report growth and unique properties of a new highly distorted 3D perovskite, methylhydrazinium lead chloride (CH3NH2NH2PbCl3, MHyPbCl 3 ). This perovskite crystallizes in polar P21 structure at room temperature, which consists of two types of PbCl6 octahedra: one weakly and another strongly deformed. The unusual deformation of every second perovskite layer is forced by the large size of methylhydrazinium cations and the ability of NH2 + terminal groups of methylhydrazinium cations to form coordination bonds with Pb2+ metal centers. On heating, MHyPbCl 3 undergoes a phase transition at 342 K into another polar Pb21 m phase with ordered organic cations. Temperature-resolved second-harmonic generation (TR-SHG) measurements confirm acentricity of both phases and show that second-harmonic response is enhanced for the high-temperature Pb21 m phase. This intriguing property of MHyPbCl 3 has been employed to demonstrate an unprecedented kind of quadratic nonlinear optical switching in which a second-harmonic response is switched between a room-temperature, low-SHG state and a high-temperature, high-SHG state. X-ray diffraction shows that enhancement of polar properties is due to rearrangement of the perovskite’s organic substructure. There is a clear pyrocurrent peak, but switching of the electric polarization could not be observed. Optical studies showed that MHyPbCl 3 is a wide-bandgap material with a bandgap of 3.4 eV (365 nm). At low temperatures, it exhibits weak UV emissions at 362 and 369 nm as well as a strong broadband white emission.

Rare Earth‐Free Luminescent Materials for WLEDs: Recent Progress and Perspectives

“…Additionally, the fluorescence intensity after heating was significantly reduced. [ 90 ] Xu et al synthesized a ternary 0D multicomponent organometallic halide formed by the co‐crystallization of organic cations HMTA+ (HMTA+: N ‐benzyl hexamethylenetetramium, C 13 H 19 N 4+ ) with three metal halides (PbBr 4 2− , MnBr 4 2− , and SnBr 4 2− ). This combination can achieve near‐perfect white light emission with CIE coordinates of (0.32, 0.33), CRI of 95, and PLQY of up to 73%.…”

“…Additionally, the fluorescence intensity after heating was significantly reduced. [90] ). This combination can achieve near-perfect white light emission with CIE coordinates of (0.32, 0.33), CRI of 95, and PLQY of up to 73%.…”

Layered Metal‐Halide Perovskite Single‐Crystalline Microwire Arrays for Anisotropic Nonlinear Optics

“…Chiral organic cations between the metal‐halide octahedral quantum wells have introduced chirality and enhanced structure polarization into the layered perovskites, allowing crystalline noncentrosymmetry, thus extending their applications in chiroptoelectronics, spintronics, and second harmonic generation (SHG). [ 11–15 ] For example, ( R )/( S )‐methylbenzylamine, ( R )/( S )‐β‐methylphenethylamine, and ( R )/( S )‐1‐(4‐chlorophenyl)ethylamine have been incorporated in perovskites as organic components to break the inversion symmetry of lattices, thus underpinning ferroelectricity, circular dichroism activity, and SHG. [ 16–19 ] These studies on halide perovskites in nonlinear optics (NLO) mainly focus on polycrystalline film and bulk crystals.…”

The Opto-Electronic Functional Devices Based on Three-Dimensional Lead Halide Perovskites

“…B represents cation locating in the center of octahedron, which could be Pb 2+ , Sn 2+ , and Ge 2+ in the more generalized cases of MHPs [2][3][4] but restricted to be Pb 2+ for LHPs. A represents the cation locating in the vacancy of neighboring octahedron cages, which could be either organic or inorganics: the inorganic examples include Cs + [5], while the organic examples include the methylammonium [6,7], formamidinium [8,9], and recently discovered methylhydrazinium [10,11]. It is expected that inorganic counterparts generally maintain better chemical stability than their organic counterparts [12].…”