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Chiral hybrid organic–inorganic metal halides (HOMHs) offer an ideal platform for the advancement of second‐order nonlinear optical (NLO) materials owing to their inherent noncentrosymmetric structures. The enhancement of optical nonlinearity of chiral HOMHs could be achieved by matching the free exciton and/or self‐trapped exciton energy levels with desired NLO frequencies. However, the current scarcity of resonance modes and low resonance ratio hamper the further improvements of NLO performance. Herein, we propose a new resonant channel of charge transfer (CT) excited states from metal halide polyhedra to organic ligand to boost the second‐order optical nonlinearity of chiral HOMHs. The model lead halide (C7H10N)PbBr3 (C7H10N=1‐ethylpyridinium) exhibits a drastically enhanced second harmonic generation in resonance to the deep CT exciton energy, with intensity of up to 111.0 times that of KDP and 10.9 times that of urea. The effective NLO coefficient has been determined to be as high as ~40.2 pm V−1, balanced with a large polarization ratio and high laser damage threshold. This work highlights the contribution of organic ligands in the construction of a resonant channel for enhancing second‐order NLO coefficients of metal halides, and thus provides guidelines for designing new chiral HOMHs materials for advanced nonlinear photonic applications. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) organic-inorganic hybrid perovskites feature characteristics of inherent quantum-well structures and intriguing optoelectronic properties, and have therefore attracted enormous research attention for their optical applications in light emitting, sensing, modulation, and telecommunication devices. The low-cost and solution-processed fabrications as well as alternative organic spacer cations endue 2D hybrid perovskites with higher tunability in optical and photonic applications. In particular, they demonstrate distinguished nonlinear optical characters such as second-harmonic generation (SHG), two-photon absorption (2PA), and saturable absorption (SA) under the excitation of laser pulses. Here, we discuss the construction of the various sorts of 2D hybrid perovskites with different structural features. We have also highlighted some representative properties and applications of these 2D hybrid perovskites in both linear and nonlinear optical regimes.

Hybrid organic−inorganic metal halides (HOMHs) have emerged as an ideal platform for the construction of semiconductor materials with promising optoelectronic properties. A number of HOMHs based on different metals including Sb3+ have been demonstrated with second‐harmonic generation (SHG) properties, but their nonlinear optical (NLO) performances including effective conversion wavelength range, optical stability, and NLO coefficients are not yet satisfactory. Here, by adopting a molecular design involving fluorine‐substitution on the achiral organic ammonium, this work has synthesized single crystals of two new chiral noncentrosymmetric HOMHs, (2‐FPEA)2SbX5 (X = Cl and Br), with large polarization ratios and outstanding optical transparency. The second‐order NLO coefficients of (2‐FPEA)2SbCl5 and (2‐FPEA)2SbBr5 are determined to be ≈24.3 and 21.6 pm V−1. Significantly, the Sb3+‐based HOMHs enable very high thermal stability and laser resistance. The distinguished laser‐induced damage thresholds (LDTs) have been estimated to be as high as 3.44 mJ cm−2 for (2‐FPEA)2SbCl5 and 3.32 mJ cm−2 for (2‐FPEA)2SbBr5, higher than that of the reported HOMHs. Such a highly efficient SHG performance and stability indicate the promising future of these Sb3+‐based metal halides for nonlinear photonic applications. [ABSTRACT FROM AUTHOR]

Chiral hybrid organic−inorganic perovskites (HOIPs) with intrinsic noncentrosymmetry have shown great potentials for chiroptoelectronic applications including second‐order nonlinear optics (NLO). Ideal NLO materials should simultaneously feature a large NLO coefficient, wide optical transparency, high laser damage threshold, and physicochemical stability. However, the development of applicable second‐order NLO materials has been largely restricted due to their strict requirement on structural noncentrosymmetry. Here, chiral amino acids abundant in nature have been adopted to synthesize hybrid lead halide perovskites (D‐/L‐Pro)PbI3·H2O (Pro = Proline) with resonance enhanced second‐harmonic generation (SHG). Their crystals feature balanced NLO performances with a large NLO coefficient, wide transparent region, high laser damage threshold, and high polarization ratio. This work demonstrates the promise of naturally abundant amino acids for the construction of hybrid chiral metal halide perovskites for next generation optoelectronic materials. [ABSTRACT FROM AUTHOR]

Chiral hybrid organic–inorganic metal halides (HOMHs) with intrinsic noncentrosymmetry have shown great promise for applications in second‐order nonlinear optics (NLO). However, established chiral HOMHs often suffer from their relatively small band gaps, which lead to negative impacts on transparent window and laser‐induced damage thresholds (LDT). Here, we have synthesized two chiral HOMHs based on CuI halides, namely (R‐/S‐MBA)CuBr2, which feature well‐balanced NLO performances with a highly efficient SHG response, outstanding optical transparency, and high LDT. The effective second‐order NLO coefficient of (R‐MBA)CuBr2 has been determined to be ≈24.7 pm V−1, which is two orders of magnitude higher than that of their CuII counterparts. This work shows the promising potential of CuI‐based chiral HOMHs for nonlinear photonic applications in wide wavelength regions. [ABSTRACT FROM AUTHOR]

Chiral hybrid perovskites have shown great potential for applications in next‐generation optoelectronic devices. The intrinsic asymmetric structures of these chiral hybrid perovskites make them particularly promising for second‐order nonlinear optics (NLO). However, it remains still a challenge to obtain ideal perovskite NLO crystals featuring simultaneously large NLO coefficient, good optical transparency, high laser damage threshold, and stable physical and chemical properties, which are highly desirable for practical applications. Herein, a series is constructed of 1D chiral lead halide hybrid perovskites (R/S‐2‐MPD)PbX3 (2‐MPD = 2‐methylpiperidine; X = Cl, Br, I) featuring non‐centrosymmetric architectures. Among them, the (R/S‐2‐MPD)PbBr3 perovskites demonstrate superior performances in second‐order optical nonlinearity, including a large second‐harmonic generation coefficient (≈29.9 pm V–1), wide transparency region (λUV ≈ 310 nm), high laser damage threshold (≈2.84 mJ cm–2), high polarization ratio (up to 96%), and robust physical and chemical stabilities. Such a balanced performance of the chiral lead halide perovskites promises their advanced application in next‐generation photonics devices. [ABSTRACT FROM AUTHOR]

Strong coupling is a distinct light–matter interaction regime, in which the interaction is manifested in coherent oscillations of energy between matter and a photonic subsystem. The consequence of such a strong coupling is the adjustment of the energy states of molecules and materials, which can bring about fascinating chemical and physical properties, and therefore result in advanced applications in many fields such as Bose–Einstein condensation and coherent emission, polariton lasing, superfluidity, quantum information processing, Raman scattering, chemical landscape, etc. Recently, strong coupling has also demonstrated profound impacts on the nonlinear optical (NLO) properties of molecular materials. In this review, the recent research progress in the field of strongly coupled systems for NLO applications is summarized. The underlying concepts and the detailed features of strongly coupled molecular systems are introduced, and the NLO characteristics of strongly coupled systems are reviewed. Finally, an outlook of future directions for this emerging field is given. [ABSTRACT FROM AUTHOR]

2D metal‐organic frameworks (MOFs) have attracted broad research interest in recent years owing to their unique dimension‐related properties for widespread applications in catalysis, energy storage, conductivity, and optoelectronic devices. In this review, first the strategies for the rational design and precise construction of 2D MOFs are introduced. Then, the synthesis of 2D MOFs and their nanosheets by using top‐down and bottom‐up methods are summarized. Subsequently, the recent advances in optical/photonic applications of these 2D MOFs are highlighted, with special focus on lighting and display devices, nonlinear optics, as well as the luminescent sensing and biomedicine applications. Finally, the future potentials and challenges for the construction of 2D MOFs for optical materials are outlooked. [ABSTRACT FROM AUTHOR]

Recent years have witnessed the prosperous developments of crystalline materials based on diverse organic/inorganic small molecules, metal organic frameworks (MOFs), covalent organic frameworks (COFs), etc. In terms of luminescent species encapsulated host-guest MOFs, Prof. Xian-He Bu and co-workers provide a comprehensive review on the construction strategies and optical applications of luminescent particles hybridized MOFs materials (adom.202100283). Lead halide perovskites have recently emerged as highly promising optoelectronic materials owing to their low-cost solution fabrication, chemical versatility, tolerance to defects, large absorption coefficient, and high charge carrier mobility. [Extracted from the article]

Intramolecular charge transfer (ICT) compounds have attracted wide attention for their potential applications in optoelectronic materials and devices such as fluorescent sensors, dye-sensitized solar cells, organic light emitting diodes and nonlinear optics. In this work, we have synthesized a new ICT compound, dimethyl-[4-(7-nitro-benzo[1,2,5]thiadiazol-4-yl)-phenyl]-amine (BTN), and have fabricated it into low dimensional micro/nano structures with well-defined morphologies. These self-assembled nanostructures exhibit high efficiency solid state fluorescence via an aggregation induced emission mechanism, which overcomes the defect of fluorescence quenching caused by aggregation in the solid state of traditional luminescent materials. We also explored and studied the nonlinear optical properties of this material through the Z-scan method, and found that this material exhibits large third-order nonlinear absorption and refraction coefficients, which promises applications of the materials in the fields of nonlinear optics and optoelectronics. [ABSTRACT FROM AUTHOR]

Abstract In this work, four intramolecular charge transfer (ICT) compounds, TBT , TVBVT , TSBST and TSVBVST , with difluoroboron β-diketonate as the electron acceptor, triphenylamine unit as the electron donor and different π-conjugated bridges have been synthesized. The linear absorption and emission spectra in different organic solvents indicate a positive solvato-chromism. The multilinear regression analyses of the linear optical spectra in different solvents indicate that the solvato-chromism is mainly caused by the polarity/dipolarity properties of the solvents and possibly the halogen-halide interaction. Time-dependent density functional theory (TD-DFT) calculations were used to investigate the charge density difference between the ground and excited states of the complex molecules of interest and the ICT processes of the excited molecules were verified. The nonlinear optical properties of the molecules were studied using a Z-scan technique. It is found that not only the structure of the molecules influences the nonlinear optical properties, but that also the solvent-solute interaction plays an important role. Highlights • Four D-A-π-A-D type BF 2 bdks compounds were designed and synthesized. • The structure and solvent-solute interaction both altered their linear optical properties. • >The solvent-solute interactions may strongly influence their third-order nonlinear refractive properties. [ABSTRACT FROM AUTHOR]