Grain-growth Inhibitor with Three-section-sintering for Highly Dispersed Single-crystal NCM90 Cubes

Single crystallization of LiNix Coy Mn1-x-y O2 (NCM) is currently an effective strategy to improve the cycling life of NCM cathode, owing to the reduced surface area and enhanced mechanical strength, but the application of single crystal NCM(SC-NCM) is being hindered by severe particle agglomeration and poor C-rate performance. Here, a strategy of three-section-sintering(TSS) with the presence of grain-growth inhibitor was proposed, in which, the TSS includes three sections of phase-formation, grain-growth and phase-preservation. While, the addition of MoO3 inhibits the grain growth and restrains the particle agglomeration. With the help of TSS and 1 mol % of MoO3 , highly dispersed surface Mo-doped SC-NCM(MSC-NCM) cubes are obtained with the average diameter of 1.3 μm. Benefiting from the surface Mo-doping and the reduced surface energy, the Li+ -migration preferred (1 0 4) crystalline facet is exposed as the dominant plane in MSC-NCM cubes, because of which, C-rate performance is significantly improved compared with the regular SC-NCM. Furthermore, this preparation strategy is compatible well with the current industrial production line, providing an easy way for the large-scale production of SC-NCM.

Hollow STW-Type Zeolite Single Crystals with Aluminum Gradient for Highly Selective Production of p-Xylene from Methanol-Toluene Alkylation

Zeolites with uniform micropores are important shape-selective catalysts. However, the external acid sites of zeolites have a negative impact on shape-selective catalysis, and the microporosity may lead to serious diffusion limitation. Herein, we report on the direct synthesis of hierarchical hollow STW-type zeolite single crystals with a siliceous exterior. In an alkalinous fluoride medium, the nucleation of highly siliceous STW zeolites takes place first, and the nanocrystals are preferentially aligned on the outer surface of the gel agglomerates to grow into single crystalline shells upon crystallization. The lagged crystallization of the internal Al-rich amorphous gels onto the inner surface of nanocrystalline zeolite shells leads to the formation of hollow cavities in the core of the zeolite crystals. The hollow zeolite single crystals possess a low-to-high aluminum gradient from the surface to the core, resulting in an intrinsic inert external surface, and exhibit superior catalytic performance in toluene methylation reactions.

Unsymmetrically Chlorinated Non-Fused Electron Acceptor Leads to High-Efficiency and Stable Organic Solar Cells

Searching the cost-effective organic semiconductors is strongly needed in order to facilitate the practice of organic solar cells (OSCs), yet to be fulfilled. Herein, we have succeeded in developing two non-fused ring electron acceptors (NFREAs), leading to the highest efficiency of 16.2 % for the NFREA derived OSCs. These OSCs exhibit the superior operational stabilities under one sun equivalent illumination without ultraviolet (UV) filtration. It is revealed that the modulation of halogen substituents on aromatic side chains, as the new structural tool to tune the intermolecular interaction and optoelectronic properties of acceptors, not only promotes the interlocked tic-tac-toe frame of three-dimensional stacks in solid, but also improves charge dynamics of acceptors to enable high-performance and stable OSCs.

Efficient Broadband Near-Infrared Emission from Lead-Free Halide Double Perovskite Single Crystal

Ultra-broadband near-infrared (NIR) luminescent materials are the most important component of NIR light-emitting devices (LED) and are crucial for their performance in sensing applications. A major challenge is to design novel NIR luminescent materials to replace the traditional Cr³⁺ -doped systems. We report an all-inorganic bismuth halide perovskite Cs₂ AgBiCl₆ single crystal that achieves efficient broadband NIR emission by introducing Na ions. Experiments and density functional theory (DFT) calculations show that the NIR emission originates from self-trapped excitons (STE) emission, which can be enhanced by weakening the strong coupling between electrons and phonons. The high photoluminescence quantum efficiency (PLQY) of 51 %, the extensive full width at half maximum (FWHM) of 270 nm and the stability provide advantages as a NIR luminescent material. The single-crystal-based NIR LED demonstrated its potential applications in NIR spectral detection as well as night vision.

Hierarchical Multi-Diameter Single-Crystal Silicon Nanowires by Successive Wet Chemical Etching

A simple and low cost top–down wet chemical etching method was developed to fabricate hierarchical multi-diameter well-ordered single-crystal silicon nanowires. The procedure starts with forming single diameter silicon nanowire arrays by using nanosphere lithography and metal-assisted chemical etching of single crystal silicon wafer, which is followed by anisotropic radial etching of the wires. Successive repetitions of these etching steps result in arrays of multi-diameter single crystal nanowires. This technique can allow engineering nanowires in a hierarchical three-dimensional geometry for the development of advanced nano devices.

Conoscopy as a Failure Analysis Method for Single Crystals

Conoscopy is widely used to evaluate single crystals used as substrates on which epitaxial layers are grown in the LED industry, where the quality of the single crystal affects the reliability of the final product, the LED chip, and the package. However, the application of this method is currently restricted to characterizing birefringence. We performed conoscopy measurements on single crystals with failure modes (e.g., birefringence, lineages, dislocations, polycrystallinity, and amorphousness) and examined whether it was possible to inspect such failures using conoscopy. Sapphire (α-Al2O3) and silicon carbide (6H–SiC) single crystals containing failures were investigated. X-ray diffraction and transmission electron microscopy analyses were also performed; their results were compared with the conoscopy results. Conoscopy was shown to inspect birefringence as well as other failure modes. Comparison of the conoscopic patterns obtained via simulation and experiment shows that quantitative evaluation of the failure level is possible. These results show that conoscopy can be used to quickly and easily investigate various failure mechanisms in single crystals.