Electronic Materials Letters最新文献

La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF), a perovskite material, is widely recognized as an excellent catalyst for the oxygen evolution reaction (OER). An anion doping strategy was implemented to enhance the presence of highly oxidation-active O²⁻/O⁻ species crucial for the electrochemical reaction, effectively replacing oxygen. The introduction of 5 mol% fluorine to LSCF resulted in improved OER performance, comparable to that of commercial noble catalysts. Furthermore, we confirmed that fluorine-doped LSCF enhanced the oxygen reduction reaction (ORR) performance, establishing its effectiveness as a bifunctional catalyst. Moreover, when utilized as an air electrode in a homemade zinc-air battery cell, the electrochemical performance of the doped LSCF remained stable after repeated charge/discharge tests. These findings underscore the potential application of anion doping in electrochemical devices.

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We report a large-area quantum dot light-emitting diode (QLED) with sputtered Zn_0.85Mg_0.15O (ZMO) as an electron transport layer (ETL). Uniform ZMO is applied as ETL of the inverted structured QLED and the adjustment of Ar/O₂ ratio on device characteristics is studied in detail. Compared to pristine ZMO, ZMOs with O₂ gas are found to be beneficial to the charge balance in the emitting layer of QLEDs mainly by their upshifted conduction band minimum, which in turn limits an electron injection. Additionally, it is found that oxygen vacancies in the ZMO, acting as the exciton quenching sites, are responsible for the device stability. QLEDs with 6:1 ZMO produce a maximum luminance of 136,257 cd/m² and external quantum efficiency of 5.15%, which are the best device performances to date among QLEDs with sputtered ETLs. These results indicate that the sputtered ZMO shows great promise for use as an inorganic ETL for future large-area QLEDs.

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Weak light detection is a current research topic and chlorine-containing lead-free perovskite materials are promising. In this research work, Cl-incorporated methylammonium Sb mixed halide perovskite (CH₃NH₃)₃ (Sb)₂(Cl)_X I_(9−X) derivatives were investigated for weak light detection. We have devised a solution-processable slow crystal growth (SCG) to fabricate 2D layered (CH₃NH₃)₃ (Sb)₂(Cl)_X I_(9−X) lead-free perovskite microcrystals. SCG facilitate only 1.51 atomic percent chlorine incorporation confirmed in FESEM-EDS analysis and band gap 1.98 eV determines the SCG grown lead-free perovskite molecular formula to be (CH₃NH₃)₃ (Sb)₂(Cl)_X I_(9−X). FTO/ (CH₃NH₃)₃ (Sb)₂(Cl)_X I_(9−X) PMCs/FTO self-powered photodetector detect 400 nm, 1µW cm⁻² weak optical signal. (CH₃NH₃)₃ (Sb)₂(Cl)_X I_(9−X) respond to weak optical signals in the 300–600 nm wavelength range. Also, (CH₃NH₃)₃ (Sb)₂(Cl)_X I_(9−X) exhibit a high reflectance (> 70%) for the wavelength above 600 nm with its inherent thermodynamic stability is a candidate for use as a reflective layer in tandem solar cells.

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The hydrated iron fluoride (Fe₃F₈·2H₂O) with mixed valence cations is successfully synthesized through a rapid electrolytic synthesis route for the first time using low-concentration HF solution as fluorine source and cheap carbon steel as iron source. By controlling the value of current density, submicron structured hydrated iron fluoride with different grain sizes is obtained. The thermal behavior of Fe₃F₈·2H₂O under air atmosphere is studied. The product cooling to room temperature after heat treatment is FeF_2.2(OH)_0.8·0.33H₂O, which is determined by X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), Fourier transform infrared spectrometer (FT-IR), and thermogravimetry/differential scanning calorimetry (TG/DSC). The evaluation of the electrochemical performance of FeF_2.2(OH)_0.8·0.33H₂O as a cathode for lithium batteries shows that it has an initial discharge capacity as high as 580 mAh g⁻¹ in a wide voltage range of 1.0–4.5 V at a current density of 20 mA g⁻¹, but the cycle performance is not very satisfactory, only 170 mAh g⁻¹ after 50 cycles.

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Transition metal oxide MnFe₂O₄ is considered a promising anode material for Li-ion batteries owing to its high theoretical specific capacity. However, this material has two bottleneck problems, i.e., poor conductivity and serious volume expansion during cycling. In this work, MnFe₂O₄ nanoparticles were successfully encapsulated in the matrix of N-doped porous carbon via a sol–gel method. As a result, the N-doped carbon matrix enhances the electronic conductivity of the composites. The special porous structure increases the contact area between the electrode material and the electrolyte and facilitates the rapid infiltration of the electrolyte. At a calcination temperature of 400 °C, the MnFe₂O₄/C composite shows a high initial discharge specific capacity of 1207.0 mAh g⁻¹ at 0.2 A g⁻¹ and retains a reversible specific capacity of 1100.1 mAh g⁻¹ after 200 cycles. The simple design of metal oxide nanomaterials encapsulated in N-doped porous carbon provides a new direction for improving the electrochemical performance of electrode materials for Li-ion batteries.

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A brief abstract: MnFe₂O₄ nanoparticles were successfully encapsulated in the matrix of N-doped porous carbon via a sol–gel method. At a calcination temperature of 400 °C, the MnFe₂O₄/C composite shows a high initial discharge specific capacity of 1207.0 mAh g⁻¹ at 0.2 C and retains a reversible specific capacity of 1100.1 mAh g⁻¹ after 200 cycles.

For the heterogeneous alloy catalysts of water electrolysis, it has been reported that conductivity can be improved through structural modifications by introducing other elements like chalcogens. Transition metal sulfides can induce numerous lattice defects due to their unique interface formation, thereby promoting abundant active sites and facilitating electron/ion movement. In this study, we report the enhanced electrochemical activity of NiFeS formed on nickel foam (NiFeS@NF) for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) during the water electrolysis, especially, the seawater electrolysis. NiFeS@NF synthesized through a one-step electrochemical deposition had an amorphous-like highly porous structure with the aggregates of spherical nanoparticles attached to nickel foam. Compared to NiFe@NF, NiFeS@NF catalysts demonstrated a reduced overpotential by ~32 mV and ~96 mV for OER and HER, respectively, at 100 mA cm⁻² and secured electrochemical stability over 24 h. Moreover, bifunctional seawater electrolysis using NiFeS@NF as both electrodes demonstrated the reduced overpotential by ~80 mV with durability over time. This facile synthesis method for anion doping and  the enhanced and selective electrolysis of seawater without producing Cl₂ gas holds promise for the creation of high-performance electrocatalysts applicable in a wide range of hydrogen energy-related fields.

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With the growing demand for high-energy-density rechargeable batteries, lithium metal anodes have reemerged as a promising alternative to conventional graphite anodes in lithium-ion batteries. Lithium metal boasts exceptional energy storage characteristics, yet its practical application has been impeded by dendritic growth issues. Extensive research has explored various solutions, including electrode engineering through surface modification and 3D structural hosts, which often involve intricate designs and processes. This study introduces an effective approach to govern lithium metal nucleation and growth, leveraging the synergistic effects of a lithiophilic layer and surface energy diversification. Inspired by the structure of standard copper mesh grids used in transmission electron microscopy (TEM), we illustrate how subtle topographic modifications can provide a viable path to anode-free lithium metal batteries. This research represents a significant stride towards accelerated advancements in lithium metal batteries, promising higher energy density and enhanced safety for energy storage solutions.

A structure composed of various Cu–Ni–Sn IMCs would develop from severe Joule heat and excessive elemental diffusion under high-density current in the solder joints of flexible printed circuit (FPC). Herein, we firstly observed the evolution of a Cu₆Sn₅ + Cu₃Sn/(Ni,Cu)₃Sn₄ hybrid structure in a µ-Cu/NiAu/Sn/Cu solder joint for full intermetallic compounds (IMCs) interconnect of flexible electronics under isothermal aging condition by in-situ TEM. The joint was divided into two regions, the IMC type on the right region remained unchanged with dwell time prolonging, while the ratio of Cu₃Sn on the left region at various dwell times fitted the JMAK model when the kinetic parameter n picked 1.5, indicating that grain boundary diffusion was the predominant mechanism for transporting Cu atoms. The nucleation and growth of Cu₃Sn grains were finished in the Cu₆Sn₅ layer. The nucleation of a Cu₃Sn grain with a spherical cap shape was firstly captured by HRTEM, and Cu₃Sn grains underwent a transformation from columnar to equiaxed when the dwell time was increased, making the morphology of Cu₃Sn grains in a µ-Cu/NiAu/Sn/Cu solder joint significantly different from the situation in larger solder joints. This study is expected to provide an in-depth study of the microstructural evolution of micro Cu/NiAu/Sn/Cu solder joints under aging condition and thereby expand their application in the microelectronic industry.

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Polytypism in SiC has created interest and opportunity for device heterostructures and bandgap engineering in power electronic applications. As each SiC polytype possesses a different bandgap, electron mobility, and degree of anisotropy, unique interfaces can be created without changing its chemical composition. The 4H polytype is commonly used, but the 3C polytype offers high surface electron mobility with isotropic properties as the only cubic polytype. This has driven research on heteroepitaxy with limited success in traditional chemical vapor deposition chambers. Discussion on polytype control and stability has been restricted to bulk and epitaxial crystal growth, despite numerous reports of polytypic transformations occurring during other processing steps. This study revealed the polytypic transformation of 4H-SiC to 3C-SiC after high temperature annealing using high resolution cross-sectional transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). Above 1750 °C, the surface significantly roughened under a reduced pressure of Ar, whereas surface planarity was maintained under Ar atmospheric pressure. The formation of 3C-SiC islands occurred adjacent to large surface pits through an epitaxial growth process for the reduced pressure condition only. Loss of SiC stoichiometry at the surface with Si enrichment and availability of on-axis terraces enabled 3C nucleation. 3C-SiC growth was retarded using a protective carbon cap (C-cap) where defect-free single crystal 3C-SiC has a coherent interface with the 4H-SiC substrate underneath. These findings demonstrate that the 3C polytype can be stable at high temperatures, encouraging the need for a better understanding of polytype stability and control.

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