Temperature Lowering Method Research Articles

Er-doped Cs2AgBiCl6 double perovskite large single crystal for optoelectronics

Double perovskites have shown great potential in addressing the toxicity and instability concerns of lead halide perovskites for practical applications. However, the fabrication of high-quality double perovskite single crystals has remained challenging. Here, large Er-doped Cs2AgBiCl6 single crystals (SCs) with a maximum dimension of 8 mm were successfully prepared using a solution temperature-lowering (STL) method. The photoluminescence (PL) spectra were excited by the lasers with energies below and above the band gap, and the origin of the abnormal PL peaks changing with temperature is explored. The photodetector made from the Er-doped Cs2AgBiCl6 SCs shows a significantly enhanced light responsivity and detectivity in the wavelength range from 370 nm to 660 nm compared with the undoped one, with excellent environmental and radiation stability. It reveals that the Er ions can be successfully doped into double perovskite single crystal, benefiting the application to optoelectronic devices.

Bulk growth, structural, optical and mechanical properties of N-phenylanthralinic acid organic scintillation single crystal

Single crystal of organic scintillation material N-Phenylanthralinic acid (NPAA) with the dimension of 10×4x3 mm3 was grown by the temperature-lowering method. X-ray diffraction studies and FT-IR analysis of grown crystal revealed the crystal structure and functional groups present in the crystal. The optical quality of the crystal is ascertained from absorption spectrum and optical bandgap studies. The fluorescence spectra exhibit an intense emission band at 452 nm and fluorescence lifetime is obtained to be very short fluorescence of 1.14 ns for prompt and 18.98 ns for delayed component. TG/ DTA studies reveal the thermal stability and melting point of the crystal. The feasibility of the grown crystal in device application is substantiated from various mechanical parameters such as Vickers hardness, Meyer's index, yield strength and stiffness constant. The chemical etching and surface morphologies of the specimen were examined using an optical microscope.

Growth, ultraviolet‐visible, vibrational, photoluminescence and second harmonic generation studies of Amaranth and EDTA co‐doped KDP crystals

KDP (Potassium dihydrogen phosphate) single crystals were grown from Amaranth dye and EDTA (Ethylenediaminetetraacetic acid disodium salt) mixed KDP solutions by the temperature lowering method and Sankaranarayanan-Ramasamy technique. The molar concentration of EDTA in the solutions was 1 mol%. The Amaranth concentrations were 0.001, 0.005, 0.01, 0.03 and 0.05 mol%. The growth of KDP crystals was oriented in type I and type II phase-matching directions which bring maximum second harmonic generation (SHG) efficiency to the crystals. Optical properties of Amaranth and EDTA co-doped KDP crystals (KAE) were investigated by Ultraviolet-Visible (UV-Vis) spectroscopy, FT-Raman spectroscopy, and photoluminescence. SHG efficiency of the crystals was measured by shining 1064 nm Nd:YAG laser directly into them and receiving output signals. The most important result in the study showed that KAE crystals had SHG efficiency of 1.7 and 2.4 times higher than EDTA doped KDP crystal (KE) and pure KDP crystal respectively. Then second-order nonlinear optical coefficients of these crystals were calculated. The simultaneous doping of two organic substances into KDP crystals has further enhanced their nonlinear optical characteristics.

Lead-Free, Water-Stable A3 Bi2 I9 Perovskites: Crystal Growth and Blue-Emitting Quantum Dots [A=CH3 NH3 + , Cs+ , and (Rb0.05 Cs2.95 )+

Despite the great success in the increase in the power conversion efficiency of lead halide perovskite solar cells, the toxicity of lead and the unstable nature of the materials are still major concerns for their wider implementation at the industrial level. Herein, large-size single crystals (SCs) are developed in HI solution by using a temperature lowering method and nanocrystals (NCs) of A3 Bi2 I9 perovskites [where A=CH3 NH3 + (MA)+ , Cs+ , and (Rb0.05 Cs2.95 )+ ] are formed in ethanol (EtOH) and toluene (TOL). The stability of A3 Bi2 I9 perovskite is investigated by immersing the SCs for 24 h and pellets for 12 h in water. Moreover, the A3 Bi2 I9 perovskite NCs displays a promising photoluminescence quantum yield of 17.63 % and a long lifetime of 8.20 ns.

Growth of metal halide perovskite materials

Perovskite materials, especially metal halide perovskites, exhibit excellent properties, such as large optical coefficients, high carrier mobilities, long carrier lifetimes, tunable resistivities, large X-ray attenuation coefficients, and simple processing techniques. In recent decades, perovskites have attracted significant attention in the photoelectric field due to their versatile utility in solar cells, light-emitting diodes, photodetectors, X/γ-ray detectors, and lasing. However, the wide applicability of perovskites highly depends on the quality of perovskite crystals and films. Thus far, several perovskite growth technologies and methods have emerged. Therefore, this review classified and summarized the main methods that have been employed to achieve perovskite growth in recent years, including the solution temperature-lowering (STL) method, inverse temperature crystallization (ITC), anti-solvent vapor-assisted crystallization (AVC), spin coating, and chemical vapor deposition (CVD). Through analysis and summary, it has been determined that the STL, ITC, and AVC methods are mainly used to grow high-quality perovskite single crystals. While the spin-coating method has a significant advantage in the preparation of perovskite films, the CVD method is propitious in the fabrication of a variety of morphologies of micro/nano perovskite materials. We hope that this review can be a comprehensive reference for scientific researchers to prepare perovskite-related materials.

Synthesis, crystal structure and optical property of manganese (II) halides based on pyridine ionic liquids with high quantum yield

Two novel tetrahedral Mn (II) halide single-crystals [(C7H10N)2][MnCl4] (1) and [(C7H10N)2][MnBr4] (2), based on pyridine ionic liquids, have been successfully prepared. Centimeter-sized single crystal 2 was grown through bottom seed-solution temperature-lowering method, while the 1 was synthesized by solvent slow evaporation. Structure elucidation results indicate that the two crystals crystallize in the different space groups of the same monoclinic system. Significantly, the solid crystal 2 is possessed of superior luminescence properties than 1 at room temperature. Excited by ultraviolet light, the 1 and 2 emit intense green emission bands derived from the Mn (II) 4T(G) energy level. The fluorescent lifetimes are 384.43 and 187.83 μs, respectively, and quantum yields are 82% and 12%, respectively. Furthermore, under the excitation of X-ray, the 2 exhibits prominent X-ray fluorescence performance.

Efficient Anti-solvent-free Spin-Coated and Printed Sn-Perovskite Solar Cells with Crystal-Based Precursor Solutions

Summary Tin-based perovskite solar cells (PSCs), with more consummate optical band gaps, lower exciton-binding energies, and higher charge-carrier mobility, have not attracted tremendous research efforts compared with the lead-based ones that have a record power conversion efficiency (PCE) of 24.2%. The major challenges for Sn-based research are significantly low open-circuit voltage, poor reproducibility, and environmental instability. It has been identified that the oxidation processes take place during the preparation of precursor solutions and fabrication of films, due to the low redox potential of the stannous absorption layer. Herein, we propose two strategies of crystal-resolving and recrystallization technology to reduce the oxidation process. As a result, PCEs of 8.9% (active area of 0.04 cm2) and 5.5% (active area = 1.01 cm2) are attained using the inverted p-i-n structure, which will lead to a revival of lead-free PSC research.

KH2PO4 single crystals activated with the Ti4+ ions in the form of TiO2−x × nH2O nanoparticles: Structural peculiarities, point defects, and dielectric properties

Potassium dihydrogen phosphate KH2PO4 (KDP) single crystals activated with Ti4+ ions in the form of TiO2−x × nH2O nanoparticles in the η-phase, synthesized by the sulfate method using TiOSO4 × хH2SO4 × yH2O, have been first grown by the temperature lowering method and cut from pyramidal (P) and prismatic (Pr) growth sectors. The first-performed neutron powder diffraction investigation of P and Pr samples cut from the KDP:Ti4+ crystal allowed us to reveal vacancies in the K and H sites for both samples, their number being larger in the Pr structure compared to the P one. Taking into account the deficiency of the K and H sites, full occupation of the O site, presence of Ti4+ ions in the structure, and the electroneutrality condition, a partial substitution of (PO4)3− anion by the (SO4)2− one, larger for the Pr sample, was observed. The real compositions of P and Pr samples, correlated with the cation-anion internuclear distances, were refined. The dielectric permittivity of the Pr sample was significantly lower than that of the P one; it decreases with decreasing К–O, P–O, and O···H distances and increasing deficiency of the K and H sites.

Formic acid: an accelerator and quality promoter for nonseeded growth of CH3NH3PbI3 single crystals.

With the aid of formic acid, CH3NH3PbI3 single crystal of 9 mm in length was directly harvested within 3 days via a nonseeded solution temperature-lowering (STL) method. It showed a record-narrow full width at half maximum of 13 arcsec for the high-resolution X-ray rocking curve, a low trap-state density of 3.1 × 109 cm-3, a high carrier mobility of 162 cm2 V-1 s-1 and high moisture stability. The addition of formic acid could suppress the oxidation of iodide ions in a conventional STL process, resulting in rapid growth of high-quality CH3NH3PbI3 single crystals.

Growth and Characterization of Tetraphenylphosphonium Bromide Crystal

Multiple-phenyl phosphorous compounds are a group of chemical materials that have been used as reactants, pharmaceutical intermediates, extractants, and catalysts in organic synthetic reactions. However, the crystal growth of bulk crystals of multiple-phenyl phosphorous compounds, which may expand their applications in photonics technology, have been largely overlooked. In this article, the crystal growth of tetraphenylphosphonium bromide (TPPB) has been studied in organic solvents and water. The crystal structures and crystallization features are analyzed by X-ray diffraction data. By a slow temperature-lowering method, a single-crystal of TPPB (2H2O) with the size of 27 × 20 × 20 mm3 has been obtained in water. The basic thermal and optical properties were characterized. We find that the TPPB (2H2O) crystal shows excellent transparent property in the near-IR region. Large Raman shifts and strong Raman scattering intensity indicate that TPPB is a potential candidate in Raman-scattering-based nonlinearity applications.

Crystalline Mixed Halide Halobismuthates and Their Induced Second Harmonic Generation

Mixed halide coordination has been widely used to finely tune the properties of inorganic and inorganic–organic hybrid compounds, especially for emerging perovskites materials. Despite the increasing number of reports on preparation methods and the affected functionalities, the peculiar and precise role of the doping halogens in structural regulation of the crystals and the resulting variations on the basic properties remain to be addressed. Here, to shed light into the “black box”, a new series of [NH2(CH2CH3)2]3Bi(Cl1–xBrx)6 (x = 0, 0.135, 0.255, 0.385, 0.847, and 1) single crystals were grown from the mixed halide solvents by the temperature lowering method. The correlation between the inclusion amounts of Br in the final crystals with the halide concentrations in the precursors is discussed from different perspectives. The two kinds of halogens share the same position in the mixed halide system, with every crystallographically independent halide site possessing different halogen occupancies. The mixed...

Growth, structure peculiarities, and dielectric properties of ferroelectric KDP/TiO2 single crystals

Potassium dihydrogen phosphate KH2PO4 (KDP) single crystals, both pure and with incorporated titanium dioxide TiO2 nanoparticles, are ferroelectric materials with dipole structure used in nonlinear optics, optoelectronics, and acoustooptics. To date, a comprehensive analysis of structural features and defect states in the KDP and KDP/TiO2 matrix is absent in literature data. Pure KH2PO4 (KDP) single crystals and KDP/TiO2 crystals with different TiO2 nanoparticles with anatase structure, synthesized by the sulfate and chloride methods, and with η-TiO2 structure, prepared by the sulfate method, grown by the temperature lowering method and cut from the pyramidal and prismatic growth sectors, have been investigated by the X-ray diffraction methods and by EDX spectroscopy. According to the energy-dispersive X-ray microanalysis, the sulfur content is higher in the sample with η-TiO2 and in the KDP/η-TiO2 crystal if compared with the samples with anatase and KDP/TiO2 (anatase). It was revealed that the sulfur content is higher in the prismatic growth sector if compared with the pyramidal one. Based on results of the X-ray single-crystal diffraction analysis, it is possible to assume the substitution of \( \text{PO}_{4}^{3 - } \) tetrahedra by \( \text{SO}_{4}^{2 - } \) ones in the KDP/TiO2 structures, which is greater in KDP/η-TiO2. The general composition of the KDP/η-TiO2 crystal from the prismatic growth sector with the highest titanium content can be written as \( (\text{K}_{0.950(1)} \square_{0.050} )\text{Ti}_{0.052\left( 2 \right)i} \left( {\text{H}_{2 - x}^{1 + } \square_{x} } \right)\left[ {\left( {\text{PO}_{4} } \right)_{y}^{3 - } \left( {\text{SO}_{4}^{2 - } } \right)_{1 - y} } \right] (\square \text{ - vacancies}). \) It was first found that the Ti4+ ions occupy the interstitial site (−0.048, 0.045, 0.550) in the KDP crystal matrix. Analysis of frequency-dependant dielectric characteristics revealed that the incorporation of TiO2 nanoparticles reduces the dielectric permittivity values of KDP/TiO2 samples compared with the pure KDP ones. It was found that the KDP/η-TiO2 sample has the smallest value of the dielectric permittivity.

Bulk crystal growth of hybrid perovskite material CH3NH3PbI3

Bulk crystal of tetragonal CH3NH3PbI3with dimensions of centimeters grown by a temperature-lowering method in HI solution is reported for the first time.

Structural and mechanical properties of KН2PО4 single crystals with embedded nanoparticles and organic molecules

Single crystals of KDP crystals with embedded Urea molecules and TiO2 nanoparticles have been grown from aqueous solution by the temperature lowering method. The effect of the organic molecules and nanoparticles on the structural and mechanical properties has been studied. It has been observed that addition of Urea molecules improves laser induced damage threshold and mechanical strength of the crystal, while TiO2 nanoparticles have the opposite effect. The structure and composition of KDP:Urea crystal are studied by three‐crystal X‐ray diffraction analysis, which reveals the existence of a correlation between the increase of the microhardness value and the change of the crystal lattice parameter. The surface features of KDP:TiO2 crystals are analyzed by scanning electron microscopy that reveals the presence of quasi‐equidistant growth bands caused by capture of the nanoparticles. It is shown that the rise of TiO2 nanoparticles concentration up to 10−4 wt.% and higher resulted in 3‐fold reduction of the laser damage threshold of KDP:TiO2 relative to pure KDP in [001] and [100] crystallographic directions. It is found that microhardness and fracture toughness decrease at the nanoparticles concentration of 10−3 wt.% due to crack formation at crystal lattice discontinuities. The grown crystals also have been subjected to dielectric studies.

Characterization and strong piezoelectric response of an organometallic nonlinear optical crystal: CdHg(SCN)4(C2H6SO)2

Bulk single crystals of CdHg(SCN)4(C2H6SO)2 (CMTD) have been grown by the temperature-lowering method. Refractive index measurements reveal that the refractive index nx along the c axis is much smaller than the ny and nz indices in the ab-plane. The detailed powder second-harmonic generation (SHG) measurements using 1064 nm radiation indicate that the crystal is a phase matchable nonlinear optical material which exhibits a strong SHG effect, 1.2 times that of KTiOPO4. The complete set of dielectric, elastic and piezoelectric constants of CMTD have been measured and the results show that the crystal possesses excellent piezoelectric properties of d36 = 20.40 and d14 = 17.80 pC N−1 (much larger than those of α-SiO2). The crystal exhibits a neutral layered structure consisting of the asymmetric HgS4 tetrahedron and CdN4O2 octahedron which are connected by π-conjugated –SCN– ligands. The physical properties have been interpreted on the basis of the crystal structure combined with theoretical calculations. The strong piezoelectric response and high optical SHG efficiency make CMTD a promising candidate for both piezoelectric and nonlinear optical applications.

Optical properties of KDP crystals doped with pyrenetetrasulfonic acid salt

KDP crystals with incorporated molecules of the luminophore 1,3,6,8-pyrenetetrasulfonic acid tetrasodium salt (SPA) were grown from KH2PO4 solutions by the temperature lowering method. The luminescence spectra of KDP/SPA crystals and SPA solutions in distilled water and in KH2PO4 solutions, were studied. The increase of the dye content gives rise to excimer luminescence in the solutions and in KDP crystals, which is due to the formation of associated dye molecules. SPA molecules possessing negative electrostatic potential are incorporated into the pyramidal growth sector of KDP crystal.

Growth, Characterization and Theoretical Study of a Novel Organometallic Nonlinear Optical Crystal: CdHg(SCN)4(C2H5NO)2

A novel potentially useful second harmonic generation (SHG) organometallic nonlinear optical (NLO) crystal: cadmium mercury thiocyanate bis(N-methylformamide), CdHg(SCN)4(C2H5NO)2 (CMTN), has been prepared, and large high-optical-quality single crystals with dimensions up to 30 ×27×9 mm3 have been grown by the temperature-lowering method. Its structural, physicochemical and optical properties are characterized by elemental analyses, X-ray powder diffraction, Fourier transform infrared and Raman spectroscopy, thermal analysis, powder SHG measurements and UV/Vis/NIR transmission. The specific heat has been determined to be 515.5 J mol−1 K−1 at 300 K. CMTN possesses good physicochemical stability up to 128.5∘C, exhibits powder SHG efficiencies 0.8 times that of urea and its UV transparency cutoff is 358 nm. By the use of the DFT/B3LYP/6-31G(d) method, the microscopic second order NLO behavior of CMTN has been investigated by computing the first-order hyperpolarizability together with that of CdHg(SCN)4 (CMTC) and CdHg(SCN)4(C3H8O2) (CMTG) crystals. The results have been explained based on their crystal structures.

Synthesis, growth and characterization of a third-order nonlinear optical crystal based on the borate ester with sodium supporting its structural framework

A novel third-order nonlinear optical (NLO) crystal based on the organic borate carboxylate ester, with formula [Na4(H2O)5][B{O2CCH(O)Ph}2]4 (abbreviated as LMBNa), has been prepared in aqueous solution. Single-crystal X-ray diffraction analysis reveals that the boron atom is coordinated with two L-mandelic ligands by alkoxide and carboxylate groups, forming the [B{OOCCH(O)C6H5}]− anion. The sodium cation supports its structural framework of borate anions in the formation of a cross-linked structure. Bulk single crystals of LMBNa were grown from acetonitrile/water by the temperature lowering method. Studies of its third-order NLO properties using a Z-scan technique demonstrate that the LMBNa crystal possesses a strong saturable absorption and the self-focusing effect. Its second molecular hyperpolarizability (γ) at 532 nm is calculated to be (3.9 ± 0.2) × 10−31 esu. Furthermore, dielectric experiments reveal that LMBNa has a quite low-dielectric constant (∼3.43) and shows an anisotropy of frequency dependence along the different crystallographic directions. Such dielectric behaviors will favor the application of the LMBNa crystal under the electric field. All the results indicate that LMBNa might be a potential candidate material for the third-order NLO applications.

Growth and Characterization of Organic NLO Crystal: β-Naphthol

Single crystals of β-Naphthol (βN), an organic nonlinear optical (NLO) material was successfully grown by temperature lowering method using chloroform as solvent. The initial compound was purified by repeated recrystallization process. As-grown crystals were characterized by single crystal X-ray diffraction (XRD) studies to ascertain that βN crystal crystallized in the monoclinic system with a noncemtrosymmetric space group. Vibrational frequencies of various functional groups in the crystals were derived from Fourier transform infrared (FTIR) spectroscopy and proton nuclear magnetic resonance (NMR) spectrum. Optical characterization was done using UV-Visible near-infrared (NIR) spectroscopy. The thermal behaviour of the material was studied by thermo gravimetric and differential thermal plots. Scanning electron microscopy (SEM) study was carried out on the surface of the grown crystals to investigate the nature of defects in the crystal surface and the NLO property of the crystal was tested by Nd:YAG laser as a source.

Growth of Cu 2+ and Mg 2+ doped nonlinear optical LATF crystals and their characterization

Single crystals of pure, Cu 2+ and Mg 2+ doped l-arginine trifluoroacetate (LATF) have been grown by the temperature lowering method. The presence of Cu 2+ and Mg 2+ was determined by atomic absorption spectroscopy (AAS). Single crystal X-ray diffraction studies were performed to calculate the lattice parameters of the pure and doped crystals. Absorption of these crystals was analyzed and the result confirms that they possess low absorption in the range 230–1100 nm. Thermal analysis (TGA, DTA) and Fourier transform infrared (FTIR) spectroscopy were carried out to investigate the thermal behavior and molecular vibrations of these crystals, respectively. The second harmonic generation (SHG) measurement reveals the NLO properties of pure and doped crystal. Surface morphologies of these crystals were also observed and studied in detail by atomic force microscopy.