Rear‐Passivated Ultrathin Cu(In,Ga)Se2 Films by Al2O3 Nanostructures Using Glancing Angle Deposition Toward Photovoltaic Devices with Enhanced Efficiency

In this work, for the first time, the addition of aluminum oxide nanostructures (Al₂O₃ NSs) grown by glancing angle deposition (GLAD) is investigated on an ultrathin Cu(In,Ga)Se₂ device (400 nm) fabricated using a sequential process, i.e., post‐selenization of the metallic precursor layer. The most striking observation to emerge from this study is the alleviation of phase separation after adding the Al₂O₃ NSs with improved Se diffusion into the non‐uniformed metallic precursor due to the surface roughness resulting from the Al₂O₃ NSs. In addition, the raised Na concentration at the rear surface can be attributed to the increased diffusion of Na ion facilitated by Al₂O₃ NSs. The coverage and thickness of the Al₂O₃ NSs significantly affects the cell performance because of an increase in shunt resistance associated with the formation of Na₂Se_X and phase separation. The passivation effect attributed to the Al₂O₃ NSs is well studied using the bias‐EQE measurement and J–V characteristics under dark and illuminated conditions. With the optimization of the Al₂O₃ NSs, the remarkable enhancement in the cell performance occurs, exhibiting a power conversion efficiency increase from 2.83% to 5.33%, demonstrating a promising method for improving ultrathin Cu(In,Ga)Se₂ devices, and providing significant opportunities for further applications.     

不对称金纳米结构的光致热增强效应的调控研究

提出了一种产生光致热增强效应的不对称的人工金 纳米结构,建立了物理模型并进行了计算。采用离散偶极近似(DDA)方法计算水介质环境中 该结构及其不对称性改变后对吸收光谱及近区电磁场分布的影响,进而 利用傅里叶热传导定律数值模拟了该结构产生的热增强效应。结果表明:改变纳米结构的不 对称程度会明显影响结 构的光谱吸收位置、线型和峰值强度;同时,通过调节纳米结构的不对称性也可以有效地将 磁场能转化为热能,并 在结构周围形成高度限定的局域热增强现象。本文提出的纳米结构可在较大的近红外波段范 围内调控温度,可作为纳米尺度 下精确控制光致热效应的温度和设计热等离子纳米器件之参考。     

Synthesis and characterization of nanostructured magnetoresistive Ni doped ZnO films

We report a method to produce magnetic nanostructured semiconductor films based in ZnO doped with Nickel to control their magnetic properties. The method is based on a combined diffusion–oxidation process within a controlled atmosphere chamber to produce a uniform distribution of Ni ions in the ZnO films (ZnO:Ni). The synthesis of ZnO:Ni films is reported as well as the magnetoresistive characteristics, the used method yields films with reproducible and homogeneous properties. The films were also characterized structurally by X-Ray Diffraction (XRD) and Raman spectroscopy, and by Hall–van der Pauw measurements. The XRD measurements confirm the nanocrystalline films character. The films resulted of n-type conductivity with electron concentrations of ~10²⁰ cm⁻³ in average and carrier mobilities of 5 cm²/V s. The Magnetoresistance (MR) behavior of the films at 300 K shows negative changes of ΔR~0.5% in accordance with the usual literature reports on samples produced by other methods.     

Water‐Stable,Magnetic Silica–Cobalt/Cobalt Oxide–Silica Multishell Submicrometer Spheres

A method to produce monodisperse magnetic composite spheres with diameters from less than 100 nm to more than 1 μm in water solution is reported. The spheres consist of a dielectric silica core and a cobalt/cobalt oxide shell which can be protected from further oxidation with an outer shell of silica or, alternatively, they can be covered with the polymer polyvinylpyrrolidone as a stabilizer. The formation of a uniform magnetic shell proceeds with the adsorption of metallic cobalt seeds, produced by the reduction of cobalt chloride with sodium borohydride, on a self‐assembled layer of polyelectrolytes on the silica core. In the second step, an outer silica shell can be formed by the hydrolysis and condensation of (3‐aminopropyl)trimethoxysilane and tetraethoxysilane. The double‐shell composite spheres show excellent sphericity, monodispersity, and a magnetic hysteresis loop at room temperature.     

Identification of rod dynamics under influence of Active Magnetic Bearing

The purpose of this paper is to apply the wavelet transform algorithm to identify the magnetic damping and magnetic stiffness coefficients of the drive rod with which a set of 4-pole Active Magnetic Bearing (AMB) is equipped. By taking advantage of time–frequency analysis feature, the ridge curve of rod free response after wavelet transformation can be extracted to find the natural frequency of the rod/AMB system. In other words, due to the influence of magnetized field by the AMB, the stiffness of the rod dynamics is not linear any more and can be estimated from the curve of the amplitude versus frequency by wavelet transformation. On the other hand, the nonlinear damping coefficients can be estimated from the derivative of amplitude versus amplitude by wavelet transformation of rod free vibration. It is found that the nonlinear magnetic damping coefficients are up to 2nd-order in polynomial and the stiffness coefficient is mainly of 3rd-order respectively. In addition, the identified 2nd-order damping coefficient is negative and hence implies that under specific rod displacement and speed, the dynamic of the rod/AMB system in axial direction is unstable.     

Size Effects in Sodium Ion Batteries

Sodium ion batteries (SIBs) are promising candidates for large-scale energy storage owing to the abundant sodium resources and low cost. The larger Na⁺ radius (compared to Li⁺) usually leads to sluggish reaction kinetics and huge volume expansion. One of the efficient strategies is to reduce the size of electrode materials or the components of electrolytes to a suitable scale where size effect begin to emerge, leading to the improved or varied thermodynamics, kinetics, and mechanisms of sodium storage. However, only a few systematic reviews address size effects in SIBs, which requires further attention urgently. Herein, after a brief discussion of the general size effect, the size-related kinetics, thermodynamics (equilibrium voltage and morphology), and sodium storage mechanisms (phase transition, conversion reaction, interfacial, and nanopore storage) of electrode materials are presented. The size effect on liquid, polymer, and inorganic solid-state electrolytes are discussed as well, including the size of solvent molecules, Na salts, and inorganic fillers. Finally, neutral and adverse size effects are discussed, and some useful strategies are proposed to overcome them. The deep insights into the size effect will provide instructive guidelines for developing SIBs and other new energy storage systems.     

密闭机柜磁场屏蔽效能研究

本文介绍机柜的电磁屏蔽原理和影响屏蔽效能的因素,对某舰载密闭铸铝机柜的低频磁场屏蔽效能进行了测试,得出具有工程实用价值的数据,对同类机箱机柜的屏蔽效能有参考评估作用,并针对本机柜门、结构和材料对屏蔽效能的影响给出了详细分析。     

Core-shell structure of polypyrrole grown on W18O49 nanorods for high performance gas sensor operating at room temperature

In this work, uniform core-shell structure of polypyrrole wrapped on tungsten oxide nanorods (PPy@W₁₈O₄₉ core-shell nanorods) were synthesized via a two-step process for gas-sensing applications. The core-nanorods of W₁₈O₄₉ were first grown by solvothermal method with tungsten hexachloride (WCl₆) as precursor. The PPy-shell layer was then formed uniformly on the solvothermally synthesized W₁₈O₄₉ nanorods by in-situ chemical polymerization of pyrrole monomer (Py), with sodium dodecyl benzene sulfonic acid (DBSA) as dopant and ammonium persulfate (APS) as oxidant. High dispersion of Py achieving in ethanol is proved to be crucial to form the uniform PPy-shell layer, and the layer thickness of PPy-shell is highly controlled by adjusting the Py concentration in polymeric solution. The morphology and structure of the nanocomposite were characterized systematically; it shows that the composite exhibits perfect core-shell structure of one-dimensional (1D) nanorods with average diameter of around 70–90 nm. The NH₃-sensing properties of the sensors based on the PPy@W₁₈O₄₉ core-shell nanorods were investigated at operating temperature of 15–130 °C over NH₃ concentration ranging from 1 to 200 ppm. The response magnitude of the PPy@W₁₈O₄₉ sensor can be affected seriously by temperature fluctuation, even in room temperature range (15–30 °C), and meanwhile, a temperature-dependent p-n response characteristic reversal is observed for the heteronanorods sensor. At much low room temperature of 15 °C, the present PPy@W₁₈O₄₉ nanorods show quick and sensitive response to NH₃ gas mainly due to the ultrathin, uniform PPy shell and the special heterojunction effect between p-type PPy and n-type W₁₈O₄₉. The underlying gas-sensing mechanism is analyzed.     

Highly Intensified Surface Enhanced Raman Scattering by Using Monolayer Graphene as the Nanospacer of Metal Film–Metal Nanoparticle Coupling System

It is widely accepted that surface enhanced Raman scattering (SERS) enhancement results from a combination of electromagnetic mechanisms (EM) and chemical mechanisms (CM). Recently, the nanoparticle‐film gap (NFG) system was studied due to its strong local enhancement field. However, there are still some technical limitations in establishing effective and simple ways for reliable and precise control of sub‐nanospacer. In addition, works on designing the nanospacer in NFG system for efficient interaction with target molecules for further improving SERS signals are rather limited. Here, a novel NFG system is proposed by introducing ultrathin monolayer graphene as well‐defined sub‐nanospacer between Ag NPs and Ag film (named G(graphene)‐NFG system). The new G–NFG system offers tremendous near‐field enhancement with one of the highest enhancement ratio of 1700 reported to date. These results show that the single‐layer graphene as a sub‐nanospacer renders the proposed G–NFG system with particularly strong EM enhancement (due to multiple couplings including the NP–NP couplings and NP‐film couplings) and additional CM enhancement in detecting some π‐conjugated molecules to function as a powerful tool in analytical science and the related fields.