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Polymer Controlled Growth and Wrapping of Perovskite Single Crystals Leading to Better Device Stability and Performance
摘要： Commodity scale polymer is used for controlling the nucleation and growth of single crystals of organolead halide perovskite. The polymer (polystyrene (PS)) cross-links and strongly interact with PbI2 and MAI (MAPbI3 perovskite precursors) resulting in the control of the crystallization process. The PS concentration modulates the nucleation time, crystal size and the number of perovskite single crystals. In addition, the PS based MAPbI3 crystals show an enhanced performance as well as improved thermal and environmental stability. Specifically, the PS-MAPbI3 crystals show 3 times higher photocurrent than plain MAPbI3 crystals and maintains a stable structure for more than 50 days (1200 h) under continuous 0.1 sun illumination in the air with a relative humidity of 40–45%. The improved performance and stability are attributed to the direct interaction between the PS and perovskite, which greatly reduces the ion migration, defect traps and charge recombination, and improves the carrier mobility and lifetime.
关键词： ion migration effect,photocurrent,perovskite,long-term stability,optoelectronics,crystal growth
更新于2025-09-23 15:21:01
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Fragmentation of Magica??Size Cluster Precursor Compounds into Ultrasmall CdS Quantum Dots with Enhanced Particle Yield at Low Temperatures
摘要： Colloidal small-size CdS quantum dots (QDs) are produced usually with low particle yield, together with side products such as the particular precursor compounds (PCs) of magic-size clusters (MSC). Here, we report our synthesis of small-size CdS QDs without the coexistence of the PC and thus with enhanced particle yield. For a conventional reaction of cadmium oleate (Cd(OA)2) and sulfur (S) in 1-octadecene (ODE), we show that after the formation of the PC in the pre-nucleation stage, the addition of tri-n-octylphosphine oxide (TOPO) facilitates the production of small-size QDs. We demonstrate that TOPO fragmentizes the PC that have formed, which enables the nucleation and growth of small-size QDs even at room temperature. Our findings introduce a new approach to making small-size QDs without the coexistence of the PC and with improved particle yield. Providing experimental evidence for the two-pathway model proposed for the pre-nucleation stage of colloidal binary QDs, the present study aids in the advance of non-classical nucleation theory.
关键词： crystal growth,nucleation,cadmium sulfide,magic-size clusters,quantum dots
更新于2025-09-23 15:21:01
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Fragmentation of Magica??Size Cluster Precursor Compounds into Ultrasmall CdS Quantum Dots with Enhanced Particle Yield at Low Temperatures
摘要： Colloidal small-size CdS quantum dots (QDs) are produced usually with low particle yield, together with side products such as the particular precursor compounds (PCs) of magic-size clusters (MSC). Here, we report our synthesis of small-size CdS QDs without the coexistence of the PC and thus with enhanced particle yield. For a conventional reaction of cadmium oleate (Cd(OA)2) and sulfur (S) in 1-octadecene (ODE), we show that after the formation of the PC in the pre-nucleation stage, the addition of tri-n-octylphosphine oxide (TOPO) facilitates the production of small-size QDs. We demonstrate that TOPO fragmentizes the PC that have formed, which enables the nucleation and growth of small-size QDs even at room temperature. Our findings introduce a new approach to making small-size QDs without the coexistence of the PC and with improved particle yield. Providing experimental evidence for the two-pathway model proposed for the pre-nucleation stage of colloidal binary QDs, the present study aids in the advance of non-classical nucleation theory.
关键词： crystal growth,nucleation,cadmium sulfide,magic-size clusters,quantum dots
更新于2025-09-23 15:21:01
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Precursor engineering for performance enhancement of hole-transport-layer-free carbon-based MAPbBr3 perovskite solar cells
摘要： An optimized two-step sequential deposition method to fabricate hole-transport-layer-free carbon-based methyl ammonium lead bromide (MAPbBr3) perovskite solar cells is reported. Small amounts of MABr are introduced into the PbBr2 precursor solution during the first step to prepare MAPbBr3 perovskite films (labeled as MAPB-xMABr), which promotes the conversion of PbBr2 into perovskite phase and results in denser perovskite films with increased crystallinity, lower trap density, and longer carrier lifetime. After optimization, a maximum power conversion efficiency (PCE) of 7.64% (VOC ? 1.36 V) is obtained for MAPB-0.2MABr based solar cells. Significantly, the non-encapsulated devices exhibit excellent long-term stability in ambient air (25e30 (cid:2)C and 20e30% relative humidity), showing no degradation after a year’s exposure. While, it also shows superior thermal stability with PCE retaining 95% of the initial efficiency after 120 h under thermal stress of 80 (cid:2)C and 40e70% relative humidity.
关键词： Perovskite solar cells,High stability,Precursor engineering,Hole transport layer free,Crystal growth
更新于2025-09-23 15:21:01
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Third-order NLO properties and power limiting behavior of (E)-3-(4-fluorophenyl)-1-(4-methoxyphenyl)prop-2-en-1-one under CW laser excitation
摘要： A novel chalcone derivative (E)-3-(4-fluorophenyl)-1-(4-methoxyphenyl)prop-2-en-1-one abbreviated as FMC was synthesized using Claisen-Schmidt condensation reaction method. Single crystals were grown using slow evaporation solution growth technique. The UV-Visible spectrum reveals that crystals are transparent in the visible region. The third order NLO properties of grown crystals in DMF (0.01m) have been studied using single beam z-scan technique with continuous wave DPSS laser operating at 532nm wavelength and 200mW power. The calculated values of non linear R.I, non linear absorption coefficient and magnitude of 3rd order susceptibility are of the order -0.1466×10-8 cm2W-1, 4.5×10-5cmW-1 and 1.26×10-8e.s.u respectively. The hyperpolarizability value obtained is of the order 1.044×10-27e.s.u. The crystal shows optical limiting behavior with limiting threshold of 11.2 KJcm-2. The results suggest that this material is considered as a promising candidate for future nonlinear optical device applications for continuous wave laser excitation.
关键词： chalcone derivatives,crystal growth,NLO materials,z-scan
更新于2025-09-23 15:21:01
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Preparation of Highly Oriented Porous LiCoO2 Crystal Films via Li-Vapor Crystal Growth Method
摘要： To construct better Li-ion-based batteries, highly oriented porous LiCoO2 crystal film is urgently needed for an active positive electrode. In this study, we prepared such a crystal film via the Li-vapor crystal growth method, which involves a simple reaction between the CoO substrate and Li-vapor. Highly crystalline LiCoO2 particles 2–3 μm in size were grown on the CoO substrate surface with strong relation of their orientation. The <110> and <018>-oriented LiCoO2 particles, which are preferable for Li-ion conduction, were generated on the CoO(110) substrate. On the CoO(111) substrate, LiCoO2 particles were grown with not only the <003> orientation but also the <012> orientation, suggesting that the crystal growth should follow the three-dimensional structure of the CoO and LiCoO2 lattice. Both the prepared LiCoO2 films from the CoO(110) and CoO(111) substrates exhibited stable and superior electrochemical properties for Li-ion battery cycling, indicating that the films will be useful for high-performance Li-ion-based batteries.
关键词： highly oriented porous film,LiCoO2 electrode,Li-vapor crystal growth,Li-ion batteries
更新于2025-09-23 15:21:01
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Epitaxial lateral overgrowth of GaN on nano-cavity patterned sapphire substrates
摘要： The epitaxial lateral overgrowth of GaN by metal-organic chemical vapor deposition using a nano-cavity patterned sapphire substrate (NCPSS) was investigated. The NCPSS, with a hexagonal non-close-packed nano-cavity pattern on the sapphire substrate, was fabricated by polystyrene sphere coating and size reduction by reactive ion etching, followed by deposition of alumina and thermal oxidation. The coalescence of GaN on the NCPSS was achieved by the formation of relatively large GaN islands and enhanced lateral overgrowth of the GaN islands over several nano-cavity pattern areas. The threading dislocation density (TDD) measured by cathodoluminescence measurement was significantly reduced from 2.4 108 cm-2 to 6.9 107 cm-2 by using the NCPSS. Dislocation behaviors that contribute to the reduction of TDD of the GaN layer were observed by transmission electron microscopy. Raman spectroscopy revealed that the compressive stress in the GaN layer was reduced by 21% due to the embedded nano-cavities. In addition, the diffuse reflectance of GaN on the NCPSS was enhanced by 54% ~ 62%, which is attributed to the increased probability of light extraction through effective light scattering by nano-cavities.
关键词： A1. Nanostructures,B1. Nitrides,A2. Single crystal growth,A3. Metalorganic chemical vapor deposition,A3. Nanoscale epitaxial lateral overgrowth
更新于2025-09-23 15:21:01
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Crystal size improvement of Bi-based superconducting whiskers under stress-controlled condition
摘要： Using stress-controlled amorphous precursors, we have successfully grown Bi2Sr2Ca n-1CunOy (Bi-based) high-transition temperature superconducting whiskers with large crystal-size. Especially, under a high compressive stress attained by 1 GPa pelletizing, the crystal size of a whisker was significantly enhanced up to 9.5 mm length (growth period: 96 h) which is 2.4 times larger than that of the conventional amorphous-precursors method when using similar growth conditions and substrate compositions. In addition, by using the stress-controlled precursors, the number of the obtained Bi-based whiskers were also increased by a factor of 1.8.
关键词： A2. Single crystal growth,A1. Stresses,B2. Superconducting materials,A1. Growth models
更新于2025-09-23 15:19:57
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Structural, spectral and nonlinear optical analysis of Bis(2-methyllactato)borate tetrahydrate: a new nonlinear optical crystal for laser applications
摘要： A new nonlinear optical crystal, ‘Bis(2-methyllactato)borate tetrahydrate’ (BMBT) has been crystallized by slowly evaporating the solvent. It crystallizes in the space group P21212. Sharp peaks present in powder XRD profile reveals the good crystallinity. Its transmission bandwidth (220 nm – 1100 nm) suggest that it can be used to generate UV radiation upto 220 nm and also in optoelectronic applications. Vibrations of functional groups (B-O, CH3, CO) associated with the crystal structure have been identified through FTIR and FT-Raman spectral studies. OH stretching vibrations have been observed near 3000 cm-1 clearly endorses the existence of water molecule in the BMBT structure. The chemical shifts observed in 1H and 13C NMR spectral results establishes the molecular structure of BMBT crystal. Second harmonic generation (SHG) efficiency is obtained as 0.9 times of KDP. The third order nonlinear susceptibility (χ3), nonlinear refractive index (n2) and nonlinear absorption co-efficient (β) were found using Z-scan technique. χ3 of title crystal is found to be 4.16 X10-5 esu. The existence of SHG efficiency and the enhanced χ3 value are due to the hydrogen bonded intermolecular interactions present in the BMBT crystal structure. The observed results suggest that BMBT can be used in Q-switching, mode locking and optical sensors like night vision devices.
关键词： Crystal structure,Z-scan analysis,crystal growth,NMR spectroscopy,second harmonic generation
更新于2025-09-23 15:19:57
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Lead Free, Aqua Stable A3Bi2I9 Perovskites: Crystal Growth and Blue Emitting Quantum dots [A = CH3NH3+, Cs+ and (Rb0.05Cs2.95)+]
摘要： Despite a great success in the rise in the power conversion efficiency of lead-halide perovskite solar cells, the toxicity of lead and the unstable nature of materials are the major concerns for their wide range of implementation at the industrial level. Herein, we have developed large size single crystals (SCs) in HI solution using temperature lowering method and nanocrystals (NCs) in ethanol (EtOH) and toluene (TOL) solvents of A3Bi2I9 perovskites [where, A = CH3NH3+ (MA)+, Cs+ and (Rb0.05Cs2.95)+]. The stability of A3Bi2I9 perovskite is investigated by immersing the SCs for 24 h and pellet for 12 h into water. Moreover, the A3Bi2I9 perovskite NCs displays a promising photoluminescence quantum yield of 17.63% and a longer lifetime of 8.20 ns.
关键词： Pb-Free Perovskites,Crystal Growth,High PLQY,Water Stability,Phase Transition,Nanocrystals,Low Bandgap
更新于2025-09-23 15:19:57