RESUMEN
In modern society, the investigation of highly efficient photoluminescent bulk materials with excitation-induced tunable multicolor luminescence and multiexciton generation (MEG) is of great significance to information security and the application of optoelectronic devices. In this study, two bulk Cu-based halide crystals of (C4H10NO)4Cu2Br5·Br and (C4H10NO)4Cu2I5·I·H2O, respectively, with one-dimensional structures were grown by a solvent evaporation method. Unexpectedly, (C4H10NO)4Cu2I5·I·H2O displayed excitation-induced tunable dual-color luminescence; one band is a brilliant green-yellow emission centered at 547 nm with a high photoluminescence quantum yield (PLQY) of up to 169.67%, and the other is a red emission at 695 nm with a PLQY of 75.76%. Just as importantly, (C4H10NO)4Cu2Br5·Br exhibits a strong broadband green-yellow emission at 561 nm under broad band excitation ranging from 252 to 350 nm, a long PL decay lifetime of 106.9 µs, and an ultrahigh PLQY of 198.22%. These materials represent the first two examples of 1D bulk crystals and Cu(I)-based halides that have a PLQY exceeding 100%. Combining the unusual luminescence characteristics with theoretical calculations reveals that MEG contributes to the green-yellow emission with ultrahigh PLQY > 100%, and that the red emission can be ascribed to [Cu2I5]3- cluster-centered emission. Additionally, an information encryption method was designed based on the Morse Code. The high luminescence characteristics of LED devices fabricated using the (C4H10NO)4Cu2Br5·Br and (C4H10NO)4Cu2I5·I·H2O crystals appear to lead to promising applications in solid-state lighting. This work extends the catalog of high-performance luminescent materials and also promotes application prospects of low-dimensional copper-based halides in optoelectronics.
RESUMEN
Currently, organic-inorganic hybrid cuprous-based halides are receiving substantial attention for their eco-friendliness, distinctive structures, and outstanding photophysical properties. Nevertheless, most of the reported cuprous-based halides demand deep ultraviolet excitation with a narrow excitation range that can meet the commercial requirement. Herein, zero-dimensional (0D) cuprous-based halide (C4H10N)4Cu4I8 single crystals (SCs) were synthesized, with an ultrabroad band excitation ranging 260-450 nm and a greenish-yellow emission band peaking at 560 nm. Excitingly, (C4H10N)4Cu4I8 also features a large Stokes shift of 300 nm, a high photoluminescence quantum yield (PLQY) of up to 84.66%, and a long lifetime of 137 µs. Furthermore, density functional theory calculations were performed to explore the relationship between structure and photophysical properties, and the photoluminescence performance of (C4H10N)4Cu4I8 originates from the electron interactions in [Cu2I4]2- clusters. Taking advantage of broad band excitation and excellent photoluminescent performances, a high luminescence characteristic UV-pumped light-emitting diode (LED) device with remarkable color stability was fabricated by employing the as-synthesized (C4H10N)4Cu4I8 SCs, which present the promising applications of low-dimensional cuprous-based halides in solid-state lighting.
RESUMEN
Zero-dimensional (0D) organic-inorganic hybrid halides present many fascinating photophysical properties for promising optoelectronic applications such as light-emitting diodes (LEDs), X-ray imaging, photodetectors, and anticounterfeiting. Herein, a centimeter-sized single crystal (C6H10N2)2MnCl6·2H2O with a 0D perovskite structure was obtained via a solvent evaporation method. A bright red emission at 618 nm with a larger Stokes shift of more than 300 nm and a long fluorescence lifetime of 6.21 ms were measured. Notably, a reversible PL switching from red emission to nonluminescence has been presented in the cycles of heating-cooling processes from RT to 100 °C. Furthermore, the temperature-induced luminescence shows a quick recovery after 20 conversion cycles, exhibiting excellent stability and temperature sensing. According to the structural and theoretical analyses, the temperature-induced luminescence is primarily due to hydrogen-bonding interactions between (MnCl6)4- and H2O molecules. Particularly, a temperature anticounterfeiting application has been designed based on its reversible temperature-dependent PL switching. Importantly, the ultraviolet-pumped LEDs fabricated by (C6H10N2)2MnCl6·2H2O single crystals are perfectly achieved. Anyway, this work clearly demonstrates that 0D Mn-based perovskite with temperature-dependent PL switching greatly extends its potential applications in electro-optical display, temperature sensing, and anticounterfeiting devices.
RESUMEN
In this paper, the voltage-transmittance curvesKDP crystals were measured accurately between two crossed or parallel polarizers using longitudinal electro-optic effect. The end faces of rectangular KDP samples were coated with ring-shaped electrodes using conductive silver paint (CSP). The change of half period voltage U i has been investigated. A method for quantitative characterization of residual stress has been proposed, based on deviation voltage U d. The results demonstrate that loading voltage is close to the integration of electric field intensity in crystal along the optical path when the CSP ring electrodes have a large outer radius R, small inner radius r, and long-distance d. The half-period voltage U i is also close to longitudinal half-wave voltage U π in these circumstances. The unclamped electro-optic coefficient γ63σ of KDP crystal at room temperature was measured as 10.24±0.05p m/V at the wavelength of 632.8 nm.
RESUMEN
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 (C5H11N) with electronegative oxygen, organic morpholine (C4H9NO) was easily obtained. Therefore, to design NLO crystals, we focused on combinations of stereochemically active lone-pair (SCALP) cation (Pb2+)-based chloride and bromide with morpholine molecules. In this work, two lead halide hybrid perovskite (C4H10NO)PbX3 (X = Cl, Br, abbreviated as MPbCl3 and MPbBr3, respectively) single crystals with moderate nonlinear optical properties were synthesized by a slow evaporation method. The two title crystals belong to orthorhombic space group P212121 with one-dimensional (1D) chainlike perovskite structures. Theoretical calculations revealed that the second harmonic generation (SHG) responses mainly originate from distorted {PbX6} octahedrons of the inorganic framework. Remarkably, moderate phase-matching SHG effects of about 0.70 and 0.81 times KH2PO4, large birefringences of 0.098 and 0.111 at 1064 nm, and large laser damage thresholds (LDTs) of 19.94 and 46.82 MW/cm2 were estimated for MPbCl3 and MPbBr3, respectively. This work provides a novel strategy for new purpose-designed hybrid NLO crystals by adjustment and modulation of chemical modification.
RESUMEN
Organic-inorganic hybrid Pb-halide perovskites have attracted tremendous interest due to their potential application in photovoltaic and optoelectronic fields. However, the toxicity and poor stability of Pb-halide perovskites have become key bottlenecks toward their future commercialization and industrialization. Therefore, in this work, two novel hybrid lead-free perovskite nonlinear optical (NLO) crystals (2-AMP)2BiX7·H2O (X = Cl, Br) with high stability were successfully synthesized. Both the crystals belong to the orthorhombic P212121 space group, displaying a zero-dimensional perovskite structure. The thermal, environmental, and solvent atmospheric stabilities were comprehensively investigated, with high thermal stability up to 170 °C and high environmental and high solvent atmospheric stability observed for (2-AMP)2BiBr7·H2O. First-principles calculations were carried out to study the relationship of the structure and properties. A large birefringence of 0.1368@1064 nm was determined for (2-AMP)2BiBr7·H2O, which was derived from the strong aeolotropic conjugated π-electron distribution of planar 2-aminomethylpyridium. A second-harmonic generation (SHG) effect that was 0.25 and 0.32 times that of KH2PO4 (KDP) was measured for (2-AMP)2BiCl7·H2O and (2-AMP)2BiBr7·H2O, respectively, and the stronger SHG response of bromide was attributed to the larger distortions of {BiBr6} octahedrons. This work may offer new guidance for exploration of low toxicity and high stability of perovskite NLO materials.
RESUMEN
To design nonlinear optical (NLO) materials, we focused on combinations of d10 metal cation (Cd2+)-based chloride and morpholine molecules to form organic-inorganic hybrids. The O of morpholine containing lone-pair electrons can be integrated with Cd2+ by a ligand-to-metal charge transfer (LMCT) strategy to build acentric structures benefiting from the second-order Jahn-Teller effect. Introduction of the high-electronegativity chlorine can make polyhedrons of acentric crystals more distorted and conducive to a strong second harmonic generation (SHG) response. Therefore, (Morpholinium)2Cd2Cl6 crystals were constructed and synthesized by a solvent evaporation method. (Morpholinium)2Cd2Cl6 belongs to the orthorhombic P212121 space group and shows a one-dimensional (1D) structure with distorted [CdCl6] and [CdCl4O2] octahedrons. The short cutoff edge of (Morpholinium)2Cd2Cl6 was determined to be about 230 nm. The SHG response of (Morpholinium)2Cd2Cl6 exhibited an intensity of approximately 0.73 × KDP as estimated by the powder second harmonic generation technique. Furthermore, related theoretical calculations were performed to study the relationship of the band structure, refractive anisotropy, electronic state, and nonlinear optical response. Besides, (Morpholinium)2Cd2Cl6 showed relatively good thermal stability. This work can serve as a guide for the design and synthesis of new large NLO hybrid crystals with d10 transition metals.
RESUMEN
Transient numerical calculations were carried out to predict the evolution of temperature and thermal stress in traditionally grown large-size KDP crystals during the removal process, considering two methods that are used to accomplish the crystal extraction. The influence of the crystal size and the difference of temperature between the crystal and environment on the stresses inside the KDP crystals were also investigated in detail. Results indicate that, in both processes of isolating crystals, the highest stress transfers from the crystal periphery to the internal part from the early to the later time stage. In the case of extracting the crystal from solution directly after crystallization and exposing to air, the maximum stress at the crystal periphery is larger than that inside the crystal, and the probability of failure from the outside surface of crystals is large. In the case of retaining the solution for a time after crystallization, the maximum stress in the crystal internal region is larger than that of the crystal surface, leading to a large possibility to originate cracks in the inner region. Both increased crystal sizes and increased temperature differences between the crystals and the environment at the end of crystal growth are factors which aggravate crystal cracking. The maximum stress in crystals in the case of retaining the solution is less than that in the case of extracting the solution, which brings about a decreased likelihood of cracking. Thus, retaining solution for a period of time after the growth is completed, such as 96 h, is suggested to be adopted to accomplish successful crystal extraction.
