Cu12Sb4S13量子点的光照增强阻变性能

采用热注入法制备了粒径为7.9 nm的Cu₁₂Sb₄S₁₃量子点（CAS QDs）,并利用旋涂法在室温下制备了结构为FTO/CAS QDs/Au（其中FTO为导电玻璃）的阻变存储器（RRAM）.在光照条件下,该三明治结构的RRAM呈现典型的双极性阻变开关特征,具有-0.38 V/0.42 V的低工作电压和10⁵的高阻变开关比,并表现出优异的数据保持性和耐久性.在持续工作1.4×10⁶ s和经过10⁴次快速读取后,器件阻变性能变化率小于0.1%.在光照和电场共同作用下,S^2-导电通道的形成与破坏和FTO/CAS QDs界面肖特基势垒高度的调制是FTO/CAS QDs/Au在高阻态与低阻态之间转变的原因.     

叶绿素、染料体系光电效应的研究

叶绿素光电性质的研究有特殊意义.70年代开始国内外已有很多报道, 它们有整流、光导、光伏和光解水制取氢和氧等性质^[1-5].我们也报道过叶绿素a/聚乙烯醇夹层电池的研究^[6-8]。     

Definitions and methods of calculation of the temperature-programmed retention index, ITP III. A simplified calculation method based on the extended kováts definition

When the temperature-programmed retention index, I_TP, of a compound is calculated according to the Extended Kováts Definition, the net retention volume, V, of the compound should be used. However, it has been found that I_TP values calculated from the net retention time, t, are almost the same as those from V, and in general the differences are less than 0.5 i.u. The mathematical justification for this is presented. Therefore, for the calculation of I_TP, the substitution of t for V in the Extended Kováts Definition is not only very convenient in practice but also reasonable in principle.     

Highly transparent memory states in polymer dispersed liquid crystal films

Electro-optical properties of polymer dispersed liquid crystal (PDLC) films which have reversed morphology are investigated. Highly transparent memory states, for which transmittances exceed more than 80 per cent, are observed in these PDLC films. The saturation voltage V₉₀ can be decreased by a PTF (a phase transition with a field) operation and becomes 10 times lower than that without PTF operation. A contrast ratio of more than 600 is obtained in the memory state of a thick PDLC film.     

Nonvolatile polymer memory device based on bistable electrical switching in a thin film of poly(N-vinylcarbazole) with covalently bonded C60

A functional polymer (PVK-C60), containing carbazole moieties (electron donors) and fullerene moieties (electron-acceptors) in a molar ratio of about 100:1, was synthesized via covalent tethering of C60 to poly(N-vinylcarbazole) (PVK). The molecular structure and composition of PVK-C60 were characterized by FTIR, Raman, and UV-vis absorption spectroscopy, gel permeation chromatography (GPC), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CyV). The C60-modified PVK exhibited an enhanced glass-transition temperature (Tg = 226 degrees C) and good solubility in organic solvents such as toluene, tetrahydrofuran, chloroform, and N,N-dimethylformamide (DMF). It could be cast into transparent films from solutions. For a thin film of PVK-C60 sandwiched between an indium tin oxide (ITO) electrode and an Al electrode (ITO/PVK-C60/Al), the device behaved as nonvolatile flash (rewritable) memory with accessible electronic states that could be written, read, and erased. The polymer memory exhibited an ON/OFF current ratio of more than 105 and write/erase voltages around -2.8 V/+3.0 V. Both the ON and OFF states were stable under a constant voltage stress of -1 V for 12 h and survived up to 108 read cycles at -1 V under ambient conditions.     

Impact of dendritic interface modifiers on phase behavior of polyvinylcarbazol-CdSe/ZnS nanocomposite films

The phase behavior of mixtures of poly(9-vinylcarbazol) (PVK) and CdSe/ZnS quantum dots (QDs) were studied depending on the nature of the surfactant used as QDs shell, namely, “native surfactant” (NS) originated from the QDs synthesis, and specially designed two-component interface modifiers comprising of dendritic phosphonic acids possessing alkyl- or cyano-terminal groups and hexyl phosphonic acid as a cosurfactant. It is shown, that the nature of interface modifier dramatically influence on distribution of QDs in the nanocomposite film. Thus, both the “native surfactant” and alkyl-containing dendritic interface modifiers favors to phase segregation of QDs in the resulting nanocomposites where two-dimensional aggregates are localized near-surface layer of the PVK film. In contrast, the cyano-containing dendritic interface modifier provides the homogeneous QDs distribution through the film thickness. We determined that the concentration quenching of QDs photoluminescence is observed for PVK/QD(NS) film. For PVK films containing QDs grafted with dendritic surfactants, the luminescent intensities increase vs QD concentration up to 80–85 wt%.     

新型Ti3C2 MXene的化学制备及基于MXene忆阻器特性与机理

阻变器件是一种微电子器件,具有阻值可在两个甚至两个以上的阻态之间重复变化的特点。忆阻器作为新型的阻变器件,具有可连续变化的丰富阻态。近年来因其具备简单的二端结构、高集成度以及低工作电压等特性,在新型非易失性存储以及构建神经形态系统等方面被广泛研究。但其在实现应用的过程中仍存在着稳定性较差等问题。近期一些工作证明了二维材料如氧化石墨烯在优化忆阻器性能方面具备良好的应用潜力。MXene是一种具备类似石墨烯结构的新型二维过渡金属碳/氮化物,因其具备二维层状结构显现出特殊的力学以及电学特性,有望应用于忆阻器中以提高器件的电学性能。在本文中,我们通过化学湿法刻蚀制备了Ti₃C₂粉末,通过旋涂工艺在忆阻器结构中引入Ti₃C₂薄膜。Ti₃C₂ MXene与SiO₂同时作为忆阻器阻变层,制备了Cu/Ti₃C₂/SiO₂/W结构的忆阻器,并且对其相关电学特性进行了探究。在该器件上,通过实验测得忆阻器典型的开关特性曲线并在双向直流电压下针对高、低阻态的可重复性、稳定性进行了实验。结果表明该器件能够在100个扫描循环过程中保持稳定的高、低阻态达到10⁴ s以上。同时,该器件状态能够受脉冲电压调节,实现突触间典型的双脉冲易化行为。实验结果表明基于Ti₃C₂ MXene的忆阻器将有望应用于构建新兴存储设备以及人工神经形态系统。     

In situ observation of smectic layer reorientation during the switching of a ferroelectric liquid crystal

A thin plastic cell containing the ferroelectric liquid crystal ZLI3654 (4 μm) was placed edge-on to a pin-hole collimated horizontal X-ray beam. In this way, the smectic layers were brought into register. Subsequently, triangular voltage waves with various peak (V_p) values were applied across the cell and diffraction photos were obtained during the application of the alternating voltage. Up to V_p = ± 30 V, no significant movements in the initial tilted orientation of the smectic layers with respect to the surfaces (chevrons) could be observed. During the application of V_p = ± 32 V an increasing fraction of the smectic layers changed their initial tilt angle with respect to the cell surfaces to make larger tilt angles. At a slightly higher voltage, the layers became upright (bookshelf structure). Upon removing the voltage and short circuiting the cell, the quasi-bookshelf structure was sustained. The new method described here can be used in combination with a fast detector for time resolved experiments.     

苝二酰亚胺:有机膦盐基双组份共混电子传输层及其开路电压接近1.0 V的非富勒烯聚合物太阳电池

The fabrication of high-efficiency organic solar cells requires a cathode interlayer (CIF) having multiple properties such as forming an ohmic contact with the active layer, high electron conductivity, low-density traps, and hole blocking. These roles can be more completely fulfilled by using a suitable binary blended CIF rather than a single molecule based CIF. In this article, we present the roles by using binary blended PDINO (amino N-oxide perylene diimide) and QPhPBr (tetraphenylphosphonium bromide) as the CIF to fabricate fullerene-free polymer solar cells (PSCs) with PBDB-T:IDTBR, a new donor: acceptor combination, as the active layer. The high-lying lowest unoccupied molecular orbital of the acceptor and the low-lying highest occupied molecular orbital (HOMO) of the polymer with small driving force (the donor-acceptor HOMO-HOMO energy offset, ∆HOMO) for the hole transfer, both result in a high open circuit voltage (V_oc). Moreover, our strategy to insert a dual mixed solution of CIF over the blended active layer better facilitates the role, which significantly improves charge extraction and collection, leading to the high V_oc, short-circuit current density (J_sc), and fill factor (FF) observed in comparison to a single CIF material. It was observed that the power conversion efficiency (PCE) increases to 8.27%, with a high V_oc of 1.0 V, using a binary mixture of CBL. Such tremendous improvements in V_oc using well known polymer donors have not been reported till date in binary solar cell systems. This idea demonstrates that the minimum energy loss because of the small ∆HOMO of the D-A combination and the use of a dual mixed layer of CBL together present the future prospects of non-fullerene photovoltaic devices for researchers.     

Properties of chemical vapour deposited nanocrystalline TiO2 thin films and their use in dye-sensitized solar cells

Nanocrystalline titanium dioxide (TiO₂) thin films have been prepared using titanium(IV) isopropoxide as a precursor onto the glass and fluorine doped tin oxide coated glass substrates by chemical vapour deposition technique at 400 °C substrate temperature. X-ray diffraction study confirms the polycrystalline nature of TiO₂ with anatase phase having tetragonal crystal structure. The films are 975 nm thick and transparent having transmittance grater than 80%. Atomic force microscopy (AFM) images reveal the nanocrystalline morphology with grain size of 200 nm. The film shows a sharp absorption edge near 350 nm. Photoelectrochemical study shows that TiO₂ thin film sensitized with Brown Orange dye is found to exhibit relatively maximum I_sc and V_oc among the studied dyes. The values of fill factor (FF) and efficiency (η) for the dye-sensitized solar cell (Brown Orange dye-sensitized TiO₂) are 0.54 and 0.17%, respectively. Such films would serve as better prospects for dye-sensitized solar cells.     

The redox of hydroxyl-assisted metallic filament induced resistive switching memory based on a biomaterial-constructed sustainable and environment-friendly device

Using biomaterial-constructed resistive switching memory devices has attracted great attention for the potential application in advanced electronic components because of their variety of advantages, such as low cost, sustainability, environment-friendly, and so on. In this work, after a series of treatments, an edible mushroom as an intermediate insulating material was assembled into an Ag/biofilm/metal structure, in which the metals such as Al, Cu, Ag, and Ti were chosen as the bottom electrode to explore in-depth physical mechanisms. The transmission mechanism of resistive switching memory behavior in an Ag/biofilm/metal device was studied in detail. It was found that the redox of hydroxyl-assisted Ag filaments could be easily formed on an inactive metal bottom electrode through the mushroom film by redox reaction under applied voltage. This work provides an ingenious potential application in wearable, flexible, sustainable, and environment-friendly biologically resistive random-access memories.     

氧化石墨烯基柔性发电机的构筑及其水蒸发发电性能

如何利用自然界广泛存在的水蒸发能是一个具有挑战性的课题。 以表面具有丰富官能团和优异亲水性的氧化石墨烯(GO)做发电材料,以肼还原制备的还原氧化石墨烯(RGO)作电极材料,通过简单滴注法在聚对苯二甲酸乙二酯(PET)衬底上构筑GO/RGO的柔性发电机,并研究其水蒸发诱导的发电性能。 结果表明,固定GO薄膜发电机的工作面积为4.5 cm×1.5 cm,以室温自然水蒸发为驱动力,可以输出90 mV的开路电势(V_oc)以及0.6 μA的短路电流(I_sc),最大功率密度可达1.25 μW/cm³。 该驱动器同时展示出优异的柔性和较高的稳定性。 通过控制体系的水蒸发发生与否,并基于经典流动电势理论,提出了水蒸发诱导的GO/RGO柔性发电机的发电机制。 提出了步骤简易、成本低廉、性能稳定的水蒸发驱动的发电机制备新思路,为新型水蒸发能的利用提供了新途径。     

A Solution‐Processable Donor–Acceptor Compound Containing Boron(III) Centers for Small‐Molecule‐Based High‐Performance Ternary Electronic Memory Devices

A novel small‐molecule boron(III)‐containing donor–acceptor compound has been synthesized and employed in the fabrication of solution‐processable electronic resistive memory devices. High ternary memory performances with low turn‐on (V_Th1=2.0 V) and distinct threshold voltages (V_Th2=3.3 V), small reading bias (1.0 V), and long retention time (>10⁴ seconds) with a large ON/OFF ratio of each state (current ratio of “OFF”, “ON1”, and “ON2”=1:10³:10⁶) have been demonstrated, suggestive of its potential application in high‐density data storage. The present design strategy provides new insight in the future design of memory devices with multi‐level transition states.     

Bipolar Resistive Switching Behavior of PVP-GQD/HfOx/ITO/Graphene Hybrid Flexible Resistive Random Access Memory

We have investigated highly flexible memristive devices using reduced graphene oxide (RGO) nanosheet nanocomposites with an embedded GQD Layer. Resistive switching behavior of poly (4-vinylphenol):graphene quantum dot (PVP:GQD) composite and HfOx hybrid bilayer was explored for developing flexible resistive random access memory (RRAM) devices. A composite active layer was designed based on graphene quantum dots, which is a low-dimensional structure, and a heterogeneous active layer of graphene quantum dots was applied to the interfacial defect structure to overcome the limitations. Increasing to 0.3–0.6 wt % PVP-GQD, V_f changed from 2.27–2.74 V. When negative deflection is applied to the lower electrode, electrons travel through the HfOx/ITO interface. In addition, as the PVP-GQD concentration increased, the depth of the interfacial defect decreased, and confirmed the repetition of appropriate electrical properties through Al and HfOx/ITO. The low interfacial defects help electrophoresis of Al⁺ ions to the PVP GQD layer and the HfOx thin film. A local electric field increase occurred, resulting in the breakage of the conductive filament in the defect.     

The role of n–p junction electrodes in minimizing the charge recombination and enhancement of photocurrent and photovoltage in dye sensitized solar cells

The composite electrode comprising n-type TiO₂ and p-type NiO oxides when sensitized with Ru-dye showed short-circuit photocurrent (I_sc) of 17 mA/cm² and open-circuit photovoltage (V_oc) of 730 mV compared to I_sc of 12 mA/cm² and 700 mV for TiO₂ electrodes. Formation of a n–p junction between TiO₂ and NiO oxide layers contributes to the enhanced photocurrent, photovoltage, fill factor and efficiency. In addition to the junction effect, NiO acts as a barrier for charge recombination leading to higher cell performance. The efficiency of the NiO coated TiO₂ solar cell is 30% more than that of bare TiO₂. The negative shift of the flat-band potential of the NiO coated TiO₂ electrode compared to TiO₂ also could be one of the reasons for higher photovoltage observed for TiO₂/NiO electrode. The highest cell efficiencies were obtained immersing TiO₂ thin films in Ni²⁺ solution and converting them to NiO by firing and the optimum NiO coating thickness was found to be only a few angstroms. The energy levels of the excited dye and the band positions of TiO₂ and NiO suggest that the electron transfer from the excited dye to the underlying n-type oxide layer occurs by tunneling through the p-type NiO layer.     

以绕丹宁和噻唑烷-2,4-二酮为端基的不对称结构有机受体分子的设计合成与构性关系探讨

分别以绕丹宁和噻唑烷-2,4-二酮单元为端基、IDT为中心核设计合成了一个新型不对称结构的有机小分子受体IDT-2,并通过与两端均以绕丹宁或噻唑烷-2,4-二酮受体单元的对称小分子受体IDT-1和IDT-3进行对比,探讨了分子结构与性能之间的关系。研究发现,从IDT-1到IDT-3,随着两端的绕丹宁基团被噻唑烷-2,4-二酮基团逐步取代,这类小分子受体的吸收光谱显著蓝移,光学带隙E_g~(opt)逐步增大,LUMO和HOMO能级也逐渐抬升。随后我们分别以这三个小分子为受体、P3HT为给体共混构建活性层而制备了有机太阳能电池,结果表明,以两端均为绕丹宁单元的对称结构小分子受体IDT-1构建的电池器件具有最高的光电转换效率(PCE),相应的J_(sc)和FF值也最大,而V_(oc)则最低;而以两端均为噻唑烷-2,4-二酮基团的对称结构小分子受体IDT-3的电池器件,其V_(oc)最高,但其J_(sc)和FF则最低,PCE值也最小。对于IDT-2而言,由于分子只有一个绕丹宁单元被噻唑烷-2,4-二酮所取代,其V_(oc),J_(sc)和PCE均介于IDT-1与IDT-3之间。由此说明,尽管噻唑烷-2,4-二酮基团的引入能有效提升器件V_(oc),但却不利于改善其J_(sc)和FF,因此受体的分子设计中如何平衡电池器件的几种光伏性能参数而获得高的光电转换效率仍是十分重要的研究课题之一。     

A novel bright blue electroluminescent polymer: poly[4,4′‐biphenylene‐α‐(9″,9″‐dihexyl‐3‐fluorenyl) vinylene]

Poly[4,4′‐biphenylene‐α‐(9”,9”‐dihexyl‐2‐fluorenyl)vinylene] (PBPHFV) was synthesized by nickel catalyzed coupling reaction of 1,2‐bis(bromophenyl)‐1‐(9”,9”‐dihexyl‐2‐fluorenyl)ethene and characterized by spectroscopic methods and elemental analysis. PBPHFV is soluble in common organic solvents. The weight average molecular weight (Mw) of PBPHFV is about 15000. PBPHFV showed good thermal stability as weight loss was less than 5 % on heating to 420 C under nitrogen atmosphere. The polymer film showed maximum absorption and emission at 370 nm and 485 nm, respectively. A bright blue electroluminescence (λ_max = 465nm, maximum intensity = 4116 cd/m²) was obtained when the device was fabricated with the structure of ITO/PEDOT/PBPHFV/LiF/Al. The turn on voltage of the device was 4.3 V and the maximum efficiency was 0.22 lm/W. When the blend with PVK (PBPHFV : PVK = 1:5) was used as an emitting layer, the maximum brightness and efficiency of the device were 9342 cd/m² and 1.66 lm/W, respectively.     

Zur chemie des galliums, 6: Tris(trimethylsilyl) silylgallium(I) —eine experimentelle und theoretische studie

The gallium(I)tris(trimethylsilyl)silyl compound {GaSi(SiMe₃)₃}₄ (1) is obtained by reaction of Ga₂Cl₄-2dioxane with LiSi(SiMe₃)₃-3THF. The crystal structure of 1 reveals a tetramer with a nearly regular tetrahedral framework of gallium atoms. The gallium-gallium distances average 258.4 pm. Ab initio calculations on various substituted gallium tetrahedrons showed a greater stability of silyl-substituted cages compared with organyl substituted ones. Crystal data, with Mo K radiation are as follows: {GaSi(SiMe₃)₃}₄ · Si(SiMe₃) ₄ (1), a, B = 1923.3(3) pm, C = 2671.2(4) pm, V = 9.881(3) nm³; tetragonal space group P4/ncc; Z = 4; 1513 ( I > 2σ(I)) data; RI = 0.068.

Zusammenfassung

Das Gallium(I)tris(trimethylsilyl)silyl-Derivat {GaSi(SiMe₃)₃}₄ (1) wird durch Umsetzung von Ga₂Cl₄-2Dioxan mit LiSi(SiMe₃)₃-3THF erhalten. Die Analyse der Kristallstruktur zeigt ein Tetramer mit einem nahezu regulären Gallium-Tetraeder-Gerüst. Der Mittelwert der Gallium-Gallium-Abstände betrügt 258.4 pm. Ab initio-Berechnungen verschiedener Gallium(I)-Verbindungen belegten eine erhöhte Stabilität von silyl-substituierten Clustern im Vergleich zu organyl-substituierten. Kristalldaten, mit Mo K -Strahlung; {GaSi(SiMe₃)₃ }₄ · Si(SiMe₃)₄ (1), a, B = 1923.3(3) pm, C = 2671.2(4) pm, V = 9.881(3) nm³; tetragonal, Raumgruppe P4/ncc; Z = 4; 1513 (I > 2 σ(I)) Daten; RI = 0.068.     

Post-modification using aluminum isopropoxide after dye-sensitization for improved performance and stability of quasi-solid-state solar cells

In this study, dye-sensitized TiO₂ electrodes were immersed into a solution of aluminum isopropoxide and after hydrolysis quasi-solid-state solar cells were fabricated. The interaction between the dye and the resulting Al₂O₃ overlayer was investigated by ultraviolet–visible (UV–vis) spectrum, Fourier transform infrared (FTIR) spectrum and X-ray photoelectron spectrum (XPS). The current density–voltage (I–V) characteristics showed that the overlayer increased the photovoltage and decreased the photocurrent under low intensity irradiation, and increased both the photovoltage and photocurrent under AM 1.5 irradiation. The Al₂O₃ overlayer at the dye/electrolyte interface resulted in a 28% improvement in overall photo-to-electrical conversion efficiency from 2.60 to 3.32%. Dark current measurements showed that Al₂O₃ acted as an insulator barrier to retard recombination between the TiO₂ and dye/quasi-solid-state electrolyte interface. Without encapsulation, dye-sensitized solar cells with Al₂O₃ coating after sensitization also exhibited improved stability compared to cells without coating.     

Ternary Conductance Switching Realized by a Pillar[5]arene-Functionalized Two-Dimensional Imine Polymer Film

Nowadays, most manufacturing memory devices are based on materials with electrical bistability (i. e., “0” and “1”) in response to an applied electric field. Memory devices with multilevel states are highly desired so as to produce high-density and efficient memory devices. Herein, we report the first multichannel strategy to realize a ternary-state memristor. We make use of the intrinsic sub-nanometer channel of pillar[5]arene and nanometer channel of a two-dimensional imine polymer to construct an active layer with multilevel channels for ternary memory devices. Low threshold voltage, long retention time, clearly distinguishable resistance states, high ON/OFF ratio (OFF/ON1/ON2=1 : 10 : 10³), and high ternary yield (75 %) were obtained. In addition, the flexible memory device based on 2DP_TPAZ+TAPB can maintain its stable ternary memory performance after being bent 500 times. The device also exhibits excellent thermal stability and can tolerate a temperature as high as 300 °C. It is envisioned that the results of this work will open up possibilities for multistate, flexible resistive memories with good thermal stability and low energy consumption, and broaden the application of pillar[n]arene.