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Visualizing different crystalline states during the infrared imaging of calcium phosphates
摘要： Methods utilizing relatively simple mathematical operations during physical analyses to enable the visualization of otherwise invisible correlations and effects are of particular appeal to researchers and students in pedagogical settings. At the same time, discerning the amorphous phase from its crystalline counterpart in materials is challenging with the use of vibrational spectroscopy and is nowhere as straightforward as in phase composition analytical methods such as X-ray diffraction. A method is demonstrated for the use of first- and second-order differentiation of Fourier transform infrared spectra of calcium phosphates to distinguish their amorphous states from the crystalline ones based on the exact line positioning rather than on comparatively vaguer band broadening and splitting effects. The study utilizes a kinetic approach, focusing on the comparison of spectral features of amorphous precursors annealed in air at different temperatures or aged for different periods of time in an aqueous solution until transforming to one or a mixture of crystalline phases, including hydroxyapatite and α- and β-tricalcium phosphate. One of the findings challenges the concept of the nucleation lag time preceding the crystallization from amorphous precursors as a “dead” period and derives a finite degree of constructive changes occurring at the atomic scale in its course. The differential method for highlighting spectral differences depending on the sample crystallinity allows for monitoring in situ the process of conversion of the amorphous calcium phosphate phase to its crystalline analogue(s). One such method can be of practical significance for synthetic solid state chemists testing for the chemical stability and/or concentration of the reactive amorphous phase in these materials, but also for biologists measuring the maturity of bone and medical researchers evaluating its phase composition and, thus, the state of metabolic and mechanical stability.
关键词： Hydroxyapatite,XRD,Derivative method,Crystallization,Amorphous,FTIR,Tricalcium phosphate
更新于2025-09-19 17:13:59
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Laser crystallized low-loss polycrystalline silicon waveguides
摘要： We report the fabrication of low-loss, low temperature deposited polysilicon waveguides via laser crystallization. The process involves pre-patterning amorphous silicon ?lms to con?ne the thermal energy during the crystallization phase, which helps to control the grain growth and reduce the heat transfer to the surrounding media, making it compatible with CMOS integration. Micro-Raman spectroscopy, Secco etching and X-ray di?raction measurements reveal the high crystalline quality of the processed waveguides with the formation of millimeter long crystal grains. Optical losses as low as 5.3 dB/cm have been measured, indicating their suitability for the development of high-density integrated circuits.
关键词： CMOS integration,low-loss,laser crystallization,polysilicon waveguides,optical losses
更新于2025-09-19 17:13:59
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Formation of thioglucoside single crystals by coherent molecular vibrational excitation using a 10-fs laser pulse
摘要： Compound crystallization is typically achieved from supersaturated solutions over time, through melting, or via sublimation. Here a new method to generate a single crystal of thioglucoside using a sub-10-fs pulse laser is presented. By focusing the laser pulse on a solution in a glass cell, a single crystal is deposited at the edge of the ceiling of the glass cell. This finding contrasts other non-photochemical laser-induced nucleation studies, which report that the nucleation sites are in the solution or at the air-solution interface, implying the present crystallization mechanism is different. Irradiation with the sub-10-fs laser pulse does not heat the solution but excites coherent molecular vibrations that evaporate the solution. Then, the evaporated solution is thought to be deposited on the glass wall. This method can form crystals even from unsaturated solutions, and the formed crystal does not include any solvent, allowing the formation of a pure crystal suitable for structural analysis, even from a minute amount of sample solution.
关键词： crystallization,coherent molecular vibrations,single crystal,thioglucoside,laser-induced nucleation
更新于2025-09-19 17:13:59
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Organic functional materials: recent advances in all-inorganic perovskite solar cells
摘要： Although the power conversion e?ciency (PCE) of organic–inorganic hybrid perovskite solar cells (PSCs) is comparable to those of commercial solar cells, a challenging problem of instability hampers their further commercialization. In recent years, in comparison with organic–inorganic hybrid PSCs, cesium-based all-inorganic perovskites show better light, moisture and especially thermal stability, and therefore they have exhibited great potential and received widespread attention. However, an unavoidable issue is that the PCE of all-inorganic PSCs still lags behind that of hybrid perovskite devices. To solve this problem, some organic or inorganic interlayer materials are introduced into all-inorganic PSCs as additive, passivation agent and charge transport materials to improve device performance. Compared to inorganic materials, organic materials present some advantages, such as energy level controllability, molecular structure diversity, and surface wettability modi?cations. Thus, the PCE of all-inorganic PSCs has been signi?cantly improved through the use of organic materials. In this review, we summarized the recent strategies for improving the performance of all-inorganic PSCs through organic interlayer materials, including crystallization control, defect passivation, interface engineering, and expanding the light harvesting capability. Finally, a perspective on challenges and opportunities is proposed in the ?eld.
关键词： organic interlayer materials,crystallization control,defect passivation,all-inorganic perovskite solar cells,light harvesting,interface engineering
更新于2025-09-19 17:13:59
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Ultra-Thick Organic Pigment Layer Up to 10 ??m Activated by Crystallization in Organic Photovoltaic Cells
摘要： Organic optoelectronic devices tend to have limited thickness. Organic light emitting diodes (OLED) and organic photovoltaic cells (OPV) made of organic pigments are typically with thickness of a few or a few tens of nanometers. Thickness of organic photovoltaic cells made with polymers exceeds them typically up to the order of a few 100 nm but still necessarily co-optimized with respect to light absorption and charge transport. Here, we demonstrate that crystallization made a 10-μm-thick pigment layer active in a photovoltaic cell, using a prototypical pair of pigments, phthalocyanine, and fullerene. It is proved that crystalline pigment layer with a thickness much greater than what is needed for optical optimization can be utilized for organic optoelectronic devices and that organic optoelectronic devices have potentiality to relief their design from co-optimization of optics and charge transport.
关键词： bulk hetero-junction,organic electronics,crystallization,organic photovoltaics,pigment,solar cell
更新于2025-09-19 17:13:59
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Crystallization of bismuth iron garnet thin films using capacitively coupled oxygen plasmas
摘要： It is demonstrated for the first time that amorphous bismuth iron garnet films can be crystallized within capacitively coupled oxygen plasmas at temperatures approximately 100 °C lower than required using conventional thermal annealing. We characterize the plasma optical emissions at high pressures (2 Torr–5 Torr) and high rf powers (500 W–800 W) and show that film crystallization is nevertheless related to thermal conditions generated in the plasma. It is demonstrated that these thermal conditions are related to the concentration of the dominant oxygen species O and O+ in the plasma, which, in turn, are a function of the rf power and pressure. The plasma treated garnet Faraday rotation and optical transmission are shown to be comparable with conventional oven or rapid thermal annealing.
关键词： capacitively coupled oxygen plasmas,thin films,bismuth iron garnet,Faraday rotation,crystallization
更新于2025-09-19 17:13:59
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Black phosphorus quantum dots in inorganic perovskite thin films for efficient photovoltaic application
摘要： Black phosphorus quantum dots (BPQDs) are proposed as effective seed-like sites to modulate the nucleation and growth of CsPbI2Br perovskite crystalline thin layers, allowing an enhanced crystallization and remarkable morphological improvement. We reveal that the lone-pair electrons of BPQDs can induce strong binding between molecules of the CsPbI2Br precursor solution and phosphorus atoms stemming from the concomitant reduction in coulombic repulsion. The four-phase transition during the annealing process yields an α-phase CsPbI2Br stabilized by BPQDs. The BPQDS/CsPbI2Br core-shell structure concomitantly reinforces a stable CsPbI2Br crystallite and suppresses the oxidation of BPQDs. Consequently, a power conversion efficiency of 15.47% can be achieved for 0.7 wt % BPQDs embedded in CsPbI2Br film-based devices, with an enhanced cell stability, under ambient conditions. Our finding is a decisive step in the exploration of crystallization and phase stability that can lead to the realization of efficient and stable inorganic perovskite solar cells.
关键词： inorganic perovskite,phase stability,Black phosphorus quantum dots,photovoltaic application,crystallization
更新于2025-09-19 17:13:59
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Enhancing Grain Growth for Efficient Solution-Processed (Cu,Ag) <sub/>2</sub> ZnSn(S,Se) <sub/>4</sub> Solar Cells Based on Acetate Precursor
摘要： Material crystallinity is the overriding factor in the determination of the photoelectric properties of absorber materials and the overall performance of photovoltaic device. Nevertheless, in Cu2ZnSn(S,Se)4 (CZTSSe) photovoltaic device the bilayer or tri-layer structure for the absorber have been broadly observed, which are generally harmful to the cell performance due to the probability of photogenerated carrier recombination at grain boundaries significantly increased. Herein, our experiment reveals that application of anions to a new family of (Cu,Ag)2ZnSn(S,Se)4 (CAZTSSe) materials leads to the increase of grain size and crystallinity. It is inspiring that by using acetate starting materials in precursor solution, a uniform, compact and pinhole-free CAZTS precursor film was obtained, and the smoothness of the films surpassed that of films fabricated from oxide route. More importantly, the crystallization of the CAZTSSe film has been considerably enhanced after selenization, large grains go through the entire absorber layer was successfully obtained. Additionally, it is observed that the Voc accompanied by excellent crystallinity improved significantly due to the pronouncedly reduced carrier recombination loss at grain boundaries. As a consequence, the power conversion efficiency (PCE) of the CAZTSSe photovoltaic device is successfully increased from 10.35% (oxide route) to 11.32% (acetate route). Importantly, our work attest to the feasibility of tuning the crystallization of the CZTSSe film by simple chemistry.
关键词： crystallization,CAZTSSe solar cell,recombination,anion,acetate starting material
更新于2025-09-19 17:13:59
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Supercooled Liquid β-Diketones with Mechanoresponsive Emission
摘要： Shear-induced crystallization of dyes in the amorphous state is an effective strategy for generating higher energy emission after mechanical perturbation—a rare phenomenon in mechanoresponsive materials. Recently, we reported that a β-diketone with a 3,4,5-trimethoxy-substituted phenyl ring formed a stable supercooled liquid (SCL) phase after melting and cooling in air. To tune the lifetime of β-diketones in the SCL phase, a series of dyes with 3,4,5-trimethoxy-substituted phenyl rings were synthesized. Derivatives with naphthyl and phenyl rings were prepared in order to modulate crystallization through arene interactions. Additionally, dyes were substituted with alkoxy chains of varying length to promote crystallization through increased van der Waals interactions. Video screening in conjunction with differential scanning calorimetry and X-ray diffraction studies indicated that naphthyl-substituted derivatives exhibited increased melted state lifetimes and that increasing the alkoxy chain length can induce crystallization. Analysis of molecular packing of single crystals of PH, PC1, PC3, and PC5 revealed that the central para-substituted methoxy group of the trimethoxy-substituted ring was forced out of the molecular plane because of steric interactions with neighboring methoxy groups. The stabilities of the SCLs were generally correlated with the torsion angles of the para methoxy groups, where derivatives with smaller angles exhibited faster rates of crystallization. Mechanical perturbation of the SCL phases resulted in shear-induced crystallization of PH, PC1, PC3, and NC6 derivatives. In some cases, traditional mechanochromic luminescence with a crystalline-to-amorphous phase transition was also observed, which indicates that some trimethoxy-substituted β-diketones exhibit more than one type of mechanoresponsive luminescence.
关键词： van der Waals interactions,supercooled liquid (SCL),mechanochromic luminescence,mechanoresponsive materials,X-ray diffraction,β-diketone,Shear-induced crystallization,differential scanning calorimetry
更新于2025-09-19 17:13:59
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Molecular Recognition and Band Alignment in 3D Covalent Organic Frameworks for Cocrystalline Organic Photovoltaics
摘要： Covalent organic frameworks (COFs) have emerged as versatile, functional materials comprised of low-cost molecular building blocks. The permanent porosity, long-range order, and high surface area of 3D-COFs permit co-crystallization with other materials driven by supramolecular interactions. We designed a new subphthalocyanine-based 3-D covalent organic framework (NEUCOF1) capable of forming co-crystals with fullerene (C60) via periodic ball-and-socket binding motifs. The high co-crystalline surface area and long-range order of NEUCOF1 eliminates the typical surface area vs. structural order trade-off in organic photovoltaics (OPVs). We used plane-wave density functional theory (PBE) to minimize NEUCOF1 and NEUCOF1–C60 co-crystals and determine their electronic band structures. Molecular dynamics (MD) simulations showed that dispersive interactions promoting co-crystallinity NEUCOF1–C60 are stable up to 350 K. The band structures at 0 and 350 K suggest that there is a driving force of 0.27 eV for exciton charge transfer to the pocket-bound fullerenes. Charge separation could then occur at the COF-C60 D-A interface, followed by the transfer of the free electron to the nanowire of C60 acceptors with a driving force of 0.20 eV.
关键词： fullerene,subphthalocyanine,co-crystallization,density functional theory,molecular dynamics,Covalent organic frameworks,organic photovoltaics
更新于2025-09-19 17:13:59