Concepts of Spin Seebeck Effect in Ferromagnetic Metals

Spin Seebeck effect (SSE) and related spin caloritronics have attracted great interest recently. However, the definition of the SSE coefficient remains to be established, let alone a clean experiment to measure the SSE coefficient in ferromagnetic metals. The concept through a model based on the semi‐classical Botlzmann transport equation has been clarified. The model includes the vital spin‐flip process, which is frequent in metals, and points out that the length scale of SSE is much larger than the spin diffusion length. The model reveals how the spin‐flip process influences the transport equations and provides the simple relationship between the different spin‐flip relaxation times for spin‐up and ‐down electrons, which is very useful to understand the spin transport properties. This understanding allows to redefine the expression of the spin Seebeck coefficient.     

Energy Filtering of Charge Carriers: Current Trends,Challenges, and Prospects for Thermoelectric Materials

Exhaustive attempts are made in recent decades to improve the performance of thermoelectric materials that are utilized for waste heat‐to‐electricity conversion. Energy filtering of charge carriers is directed toward enhancing the material thermopower. This paper focuses on the theoretical concepts, experimental evidence, and the authors' view of energy filtering in the context of thermoelectric materials. Recent studies suggest that not all materials experience this effect with the same intensity. Although this effect theoretically demonstrates improvement of the thermopower, applying it poses certain constraints, which demands further research. Predicated on data documented in literature, the unusual dependence of the thermopower and conductivity upon charge carrier concentrations can be altered through the energy filtering approach. Upon surmounting the physical constraints discussed in this article, thermoelectric materials research may gain a new direction to enhance the power factor and thermoelectric figure of merit.     

散粒噪声用于纳米电子器件与结构的量子效应表征

论述了纳米电子器件与结构中散粒噪声的产生机理和影响因素,表明散粒噪声与输运过程密切相关,按照噪声功率谱的幅值大小将散粒噪声分为泊松散粒噪声、亚泊松散粒噪声和超泊松散粒噪声四类。将散粒噪声的这些规律应用于纳米电子器件和结构,可表征不同器件与结构中的量子效应。利用散粒噪声已经成功检测到无序导线中的开放通道与量子点混沌腔中的波动性,测量出超导体与分数量子霍尔效应中的准粒子电荷。将散粒噪声用于检测纠缠态对量子计算具有重要的意义,自旋相干输运的检测是自旋电子学的重要研究课题。     

Organic Field‐Effect Transistors: A 3D Kinetic Monte Carlo Simulation of the Current Characteristics in Micrometer‐Sized Devices

The electrical properties of organic field‐effect transistors (OFETs) are usually characterized by applying models initially developed for inorganic‐based devices, which often implies the use of approximations that might be inappropriate for organic semiconductors. These approximations have brought limitations to the understanding of the device physics associated with organic materials. A strategy to overcome this issue is to establish straightforward connections between the macroscopic current characteristics and microscopic charge transport in OFETs. Here, a 3D kinetic Monte Carlo model is developed that goes beyond both the conventional assumption of zero channel thickness and the gradual channel approximation to simulate carrier transport and current. Using parallel computing and a new algorithm that significantly improves the evaluation of electric potential within the device, this methodology allows the simulation of micrometer‐sized OFETs. The current characteristics of representative OFET devices are well reproduced, which provides insight into the validity of the gradual channel approximation in the case of OFETs, the impact of the channel thickness, and the nature of microscopic charge transport.     

Design Strategies of 3D Carbon-Based Electrodes for Charge/Ion Transport in Lithium Ion Battery and Sodium Ion Battery

Advanced 3D carbon-based electrodes have the potential to significantly enhance the energy-power density of lithium ion batteries and sodium ion batteries, due to their continuous conductive networks, proper porosity distribution, and integrated stable structure. However, it still remains a fundamental scientific challenge to accurately understand the charge/ion transport in 3D carbon-based electrodes. In this review, the operating mechanism of charge/ion transport in 3D carbon-based electrodes are comprehended by introducing a useful architectural analogy to provide a physical insight. In order to better understand the relationship between 3D carbon-based electrode structure and electrode process characteristics, the main design strategies of 3D carbonbased electrodes according to the specific characteristic of pore tortuosity is proposed. Through analysis of 3D carbon electrode architectural models, several key scientific issues and related characterization technologies that are beneficial to improving the charge/ion transport efficiency are also raised. The kinetics difference of ionic transport between Li⁺ and Na⁺ ions is also taken into account. Furthermore, the critical parameters of porous structure including porosity and tortuosity to investigate the parameter-structure-performance relationships of 3D carbon-based architecture electrodes are highlighted, which in turn would guide more rational battery design in tradeoff between the high capacity and fast transport.     

In Situ Preparation of Sandwich MoO3/C Hybrid Nanostructures for High‐Rate and Ultralong‐Life Supercapacitors

This work presents a design of sandwich MoO₃/C hybrid nanostructure via calcination of the dodecylamine‐intercalated layered α‐MoO₃, leading to the in situ production of the interlayered graphene layer. The sample with a high degree of graphitization of graphene layer and more interlayered void region exhibits the most outstanding energy storage performance. The obtained material is capable of delivering a high specific capacitance of 331 F g^?1 at a current density of 1 A g^?1 and retained 71% capacitance at 10 A g^?1. In addition, nearly no discharge capacity decay between 1000 and 10 000 continuous charge–discharge cycles is observed at a high current density of 10 A g^?1, indicating an excellent specific capacitance retention ability. The exceptional rate capability endows the electrode with a high energy density of 41.2 W h kg^?1 and a high power density of 12.0 kW kg^?1 simultaneously. The excellent performance is attributed to the sandwich hybrid nanostructure of MoO₃/C with broad ion diffusion pathway, low charge‐transfer resistance, and robust structure at high current density for long‐time cycling. The present work provides an insight into the fabrication of novel electrode materials with both enhanced rate capability and cyclability for potential use in supercapacitor and other energy storage devices.     

Application of 2D MXene in Organic Electrode Materials for Rechargeable Batteries: Recent Progress and Perspectives

Organic electrode materials (OEMs) are emerging green power because of the promising advantages such as environmental friendliness, abundant sources, easy recycling, and structural diversity. However, several inherent issues, including low electronic conductivity, dissolution of active materials, and particle pulverization restrict their practical application. MXene, as a novel 2D material has exhibited enormous potential to solve the issues of OEMs due to its high conductivity, unique structure, exceptional mechanical property, and abundant surface groups. Up to now, various effective strategies have been presented and achieved positive effects, such as constructing heterojunction structures, in situ assembly, dip-coating, preparing free-standing MXene paper, etc. Nonetheless, comprehensive review of the progress and status is rare. Herein, an overview of the application of MXene in organic electrode materials for rechargeable batteries is systematically put forward. Meanwhile, recent progress and future development directions are presented. This review can serve as a guide for future research.     

Employing Interfaces with Metavalently Bonded Materials for Phonon Scattering and Control of the Thermal Conductivity in TAGS‐x Thermoelectric Materials

The thermoelectric compound (GeTe)_x(AgSbTe₂)_1?x, in short (TAGS‐x), is investigated with a focus on two stoichiometries, i.e., TAGS‐50 and TAGS‐85. TAGS‐85 is currently one of the most studied thermoelectric materials with great potential for thermoelectric applications. Yet, surprisingly, the lowest thermal conductivity is measured for TAGS‐50, instead of TAGS‐85. To explain this unexpected observation, atom probe tomography (APT) measurements are conducted on both samples, revealing clusters of various compositions and sizes. The most important role is attributed to Ag₂Te nanoprecipitates (NPs) found in TAGS‐50. In contrast to the Ag₂Te NPs, the matrix reveals an unconventional bond breaking mechanism. More specifically, a high probability of multiple events (PME) of ≈60% is observed for the matrix by APT. Surprisingly, the PME value decreases abruptly to ≈20–30% for the Ag₂Te NPs. These differences can be attributed to differences in chemical bonding. The precipitates' PME value is indicative of normal bonding, i.e., covalent bonding with normal optical modes, while materials with this unconventional bond breaking found in the matrix are characterized by metavalent bonding. This implies that the interface between the metavalently bonded matrix and covalently bonded Ag₂Te NP is partly responsible for the reduced thermal conductivity in TAGS‐50.     

MXene Electrode for the Integration of WSe2 and MoS2 Field Effect Transistors

Recently, MXenes, which are 2D early transition metal carbides and carbonitrides, have attracted wide attention because of their excellent conductivities. Here, the electrode applications of Ti₂C(OH)_xF_y, one member of the MXene family, in WSe₂ and MoS₂ field effect transistors (FETs) are assessed. Kelvin probe force microscopy analysis is performed to determine its work function, which is estimated to be ≈4.98 eV. Devices based on WSe₂/Ti₂C(OH)_xF_y and MoS₂/Ti₂C(OH)_xF_y heterostructures are fabricated with the mechanical transfer method and their electronic performances evaluated. The temperature‐dependent current–voltage transfer characteristics of the devices are determined to extract their Schottky barrier heights. The hole barrier between WSe₂ and Ti₂C(OH)_xF_y is estimated to be ≈0.23 eV and the electron barrier between the MoS₂ band and Ti₂C(OH)_xF_y is ≈0.19 eV, which indicates that the pinning effect occurs at the MoS₂/Ti₂C(OH)_xF_y interface but not at the WSe₂/Ti₂C(OH)_xF_y interface; this difference arises because of the difference between the band structures of WSe₂ and MoS₂. A complementary metal–oxide–semiconductor inverter based on these electrode properties of Ti₂C(OH)_xF_y with MoS₂ (n‐channel) and WSe₂ (p‐channel) is fabricated, which demonstrates that Ti₂C(OH)_xF_y is a promising electrode for future nanoelectronics applications.     

AlSb晶体内二维磁极化子的磁场与温度效应

在考虑声子之间相互作用的同时，本文应用线性组合算符和微扰法研究了电子自旋对弱耦合二维磁极化子特性的影响。对AlSb晶体所作的数值计算结果表明，随着磁场的加强，磁极化子平均数减少；随着温度的增加，磁极化子平均数也增加；随着温度的增加，电子自旋作用以及声子之间相互作用都加强；随着磁场的加强，电子自旋作用增加而声子之间相互作用基本不变。     

PTC欧姆铝电极浆料印烧工艺对元件性能的影响

以In/Ga电极作为参考电极,研究讨论了铝电极厚度对最终PTC元件性能的影响,并得出了最佳厚度参数。采用差热分析法,观察了在升温过程中铝电极的物理化学变化,并详细讨论了影响铝电极烧渗过程的三个重要参数:升温速度,最高烧渗温度及保温时间与元件性能的关系。得出在本电极组成条件下,最佳工艺参数:丝网目数为220目,升温时间为10 min,最高烧渗温度为660℃,保温时间为10 min。     

A Simple Cu(II) Polyelectrolyte as a Method to Increase the Work Function of Electrodes and Form Effective p-Type Contacts in Perovskite Solar Cells

One effective strategy to improve the performance of perovskite solar cells (PSCs) is to develop new hole transport layers (HTLs). In this work, a simple polyelectrolyte HTL, copper (II) poly(styrene sulfonate) (Cu:PSS), which comprises easily reduced Cu²⁺ counter-ions with an anionic PSS polyelectrolyte backbone is investigated. Photoelectron spectroscopy reveals an increase in the work function of the anode and upward band bending effect upon incorporation of Cu:PSS in PSC devices. Cu:PSS shows a synergistic effect when mixed with polyethylenedioxythiophene: polystyrenesulfonate (PEDOT:PSS) in various proportions and results in a decrease in the acidity of PEDOT:PSS as well as reduced hysteresis in completed devices. Cu:PSS functions effectively as a HTL in PSCs, with device parameters comparable to PEDOT:PSS, while mixtures of Cu:PSS with PEDOT:PSS shows greatly improved performance compared to PEDOT:PSS alone. Optimized devices incorporating Cu:PSS/PEDOT:PSS mixtures show an improvement in efficiency from 14.35 to 19.44% using a simple CH₃NH₃PbI₃ active layer in an inverted (P-I-N) geometry, which is one of the highest values yet reported for this type of device. It is expected that this type of HTL can be employed to create p-type contacts and improve performance in other types of semiconducting devices as well.     

Control of the Morphology and Structural Development of Solution‐Processed Functionalized Acenes for High‐Performance Organic Transistors

Solution‐processable functionalized acenes have received special attention as promising organic semiconductors in recent years because of their superior intermolecular interactions and solution‐processability, and provide useful benchmarks for organic field‐effect transistors (OFETs). Charge‐carrier transport in organic semiconductor thin films is governed by their morphologies and molecular orientation, so self‐assembly of these functionalized acenes during solution processing is an important challenge. This article discusses the charge‐carrier transport characteristics of solution‐processed functionalized acene transistors and, in particular, focuses on the fine control of the films' morphologies and structural evolution during film‐deposition processes such as inkjet printing and post‐deposition annealing. We discuss strategies for controlling morphologies and crystalline microstructure of soluble acenes with a view to fabricating high‐performance OFETs.     

Mechanism of Crystallization and Implications for Charge Transport in Poly(3‐ethylhexylthiophene) Thin Films

In this work, crystallization kinetics and aggregate growth of poly(3‐ethylhexylthiophene) (P3EHT) thin films are studied as a function of film thickness. X‐ray diffraction and optical absorption show that individual aggregates and crystallites grow anisotropically and mostly along only two packing directions: the alkyl stacking and the polymer chain backbone direction. Further, it is also determined that crystallization kinetics is limited by the reorganization of polymer chains and depends strongly on the film thickness and average molecular weight. Time‐dependent, field‐effect hole mobilities in thin films reveal a percolation threshold for both low and high molecular weight P3EHT. Structural analysis reveals that charge percolation requires bridged aggregates separated by a distance of ≈2–3 nm, which is on the order of the polymer persistence length. These results thus highlight the importance of tie molecules and inter‐aggregate distance in supporting charge percolation in semiconducting polymer thin films. The study as a whole also demonstrates that P3EHT is an ideal model system for polythiophenes and should prove to be useful for future investigations into crystallization kinetics.     

New Inorganic–Organic Hybrid Materials for HPLC Separation Obtained by Direct Synthesis in the Presence of a Surfactant

Nanostructured, mesoporous inorganic–organic hybrid xerogels were reproducibly synthesized by a sol–gel procedure. For the introduction of long alkyl chains into inorganic polymers, trifunctional n‐alkyltrialkoxysilanes of the type CH₃(CH₂)_nSi(OR)₃ (n = 7, 11, 17; R = CH₃, C₂H₅) were co‐condensed with Si(OEt)₄ (TEOS). The synthetic pathway involves the employment of n‐hexadecylamine as template and catalyst. The xerogels obtained by the present procedure consist of uniform spherical particles with a diameter of about 1 μm. The composition of the new materials was determined by ¹³C and ²⁹Si cross polarization magic angle spinning (CP/MAS) NMR spectroscopy. In addition, the degree of organization was investigated by small angle X‐ray and electron diffraction. In accordance with ¹³C CP/MAS NMR spectroscopic measurements, the alkyl chains form a crystalline arrangement within the silica polymer. Brunauer–Emmett–Teller (BET) adsorption measurements confirm specific surface areas of up to 1400 m²/g. The material properties prove the xerogels to be suitable as stationary phases in high‐performance liquid chromatography (HPLC). These novel mesoporous, nanostructured materials have been successfully employed in HPLC for the first time. Different standard reference materials (SRMs) containing polycyclic aromatic hydrocarbons have been separated with the xerogels described in the present work.     

Single Crystal Microwires of p‐DTS(FBTTh2)2 and Their Use in the Fabrication of Field‐Effect Transistors and Photodetectors

Single crystal microwires of a well‐studied organic semiconductor used in organic solar cells, namely p‐DTS(FBTTh₂)₂, are prepared via a self‐assembly method in solution. The high level of intermolecular organization in the single crystals facilitates migration of charges, relative to solution‐processed films, and provides insight into the intrinsic charge transport properties of p‐DTS(FBTTh₂)₂. Field‐effect transistors based on the microwires can achieve hole mobilities on the order of ≈1.8 cm² V^?1 s^?1. Furthermore, these microwires show photoresponsive electrical characteristics and can act as photoswitches, with switch ratios over 1000. These experimental results are interpreted using theoretical simulations using an atomistic density functional theory approach. Based on the lattice organization, intermolecular couplings and reorganization energies are calculated, and hole mobilities for comparison with experimental measurements are further estimated. These results demonstrate a unique example of the optoelectronic applications of p‐DTS(FBTTh₂)₂ microwires.     

A Matter of Size and Stress: Understanding the First‐Order Transition in Materials for Solid‐State Refrigeration

Solid‐state magnetic refrigeration is a high‐potential, resource‐efficient cooling technology. However, many challenges involving materials science and engineering need to be overcome to achieve an industry‐ready technology. Caloric materials with a first‐order transition—associated with a large volume expansion or contraction—appear to be the most promising because of their large adiabatic temperature and isothermal entropy changes. In this study, using experiment and simulation, it is demonstrated with the most promising magnetocaloric candidate materials, La–Fe–Si, Mn–Fe–P–Si, and Ni–Mn–In–Co, that the characteristics of the first‐order transition are fundamentally determined by the evolution of mechanical stresses. This phenomenon is referred to as the stress‐coupling mechanism. Furthermore, its applicability goes beyond magnetocaloric materials, since it describes the first‐order transitions in multicaloric materials as well.     

公共场所集中空调通风系统卫生状况及清洗消毒效果的综述

随着人民生活水平的提高,公共场所集中空调污染问题愈发受到重视.近几年经过努力,集中空调通风系统卫生状况有所改善,但是卫生安全问题仍存在,特别是送风中微生物污染问题仍较为严重.因此集中空调通风系统的卫生状况及清洗消毒效果需要进一步调查和分析研究.就相关研究进展情况进行综述.     

Deciphering the Electroluminescence Behavior of Silver(I)‐Complexes in Light‐Emitting Electrochemical Cells: Limitations and Solutions toward Highly Stable Devices

Ionic transition‐metal complexes based on silver(I) metal core (Ag‐iTMCs) represent an appealing alternative to other iTMCs in solid‐state lighting owing to (i) their low cost and well‐known synthesis, (ii) the tunable bandgap, and (iii) the highly efficient photoluminescence. However, their electroluminescence behavior is barely studied. Herein, the archetypal green‐emitting Ag‐iTMCs, namely [Ag(4,4′‐dimethoxy‐2,2′‐bipyridine)(Xantphos)]X (X = BF₄, PF₆, and ClO₄), are thoughtfully investigated, revealing their electroluminescent features in light‐emitting electrochemical cells (LECs). Despite optimizing device fabrication and operation, luminance of 40 cd m^?2, efficacy of 0.2 cd A^?1, and a very poor stability of 30 s are achieved. This outcome encourages the comprehensive study of the degradation mechanism combining electrochemical impedance spectroscopy, X‐ray diffraction, and cyclic voltammetry techniques. These results point out the irreversible formation of silver nanoclusters under operation strongly limiting the device performance. As such, LECs are further optimized by (i) changing the counterions (PF₆^? and ClO₄^?) and (ii) decoupling electron injection and exciton formation using a double‐layered architecture. The synergy of both approaches leads to a broad exciplex‐like whitish electroluminescence emission (x/y CIE of 0.40/0.44 and color rendering index of 85) with an outstanding improved stability of ≈4 orders of magnitude (>80 h) without losing brightness (35 cd m^?2).