Highly uniform electrochromic tungsten oxide thin films deposited by e-beam evaporation for energy saving systems

In the last few decades, there has been a surge of interest in using tungsten oxide thin films as an active layer of electrochromic device. These devices have several practical applications such as smart window of buildings and automobile glazing for energy saving. The main objective of this work was to construct highly homogeneous and uniform e-beam evaporated amorphous WO_3-x based films into electrochromic devices, which were fully characterized for switching speed, coloration efficiencies and cycling voltammetry responses. Fabricated devices contain indium doped transparent oxide coated glass as the transparent conductive electrode, ～200?nm thickness of WO_3-x as the cathodically coloring material and a lithium perchlorate based conducting gel electrolyte. X-ray diffraction patterns indicate that all as-deposited films are amorphous. Experimental results showed that both solid and liquid electrolyte electrochromic devices are initially very transparent that exhibit perfect optical modulation and coloration efficiency (up to 68.7?cm²/C and 52.6?cm²/C at 630?nm, respectively) due to easier intercalation of the Li⁺ within their structure. One of the more significant findings to emerge from this study is that e-beam coated electrochromic devices based on tungsten oxide thin films showed superior performance among to other coating methods. Therefore, excellent reversibility of color change behavior is attractive for pertinent use in electrochromic energy storage devices.     

Comparison of electrochromic characteristics of electrochromic device upon various sintering methods of sol-gel based WO3 electrode

Tungsten oxide is an electrochromic material, from which thin films are conventionally fabricated via heat treatment. Here, we develop a flash light sintering method to reduce sintering time; sintering delivers instantaneous photon energy created via the photothermal effect. The electrochromic efficiency of device with a flash light-sintered electrode was 88.50 cm²/C, about 1.46-fold greater than that of the device with a heat-sintered electrode. The diffusion coefficients of the former device were 1.35- and 1.46-fold greater than those of the latter device during bleaching and coloring, respectively. Therefore, a new way of sintering electrode was studied to show that the device with flash light–sintered electrode demonstrate better electrochromic performance than the device with heat-sintered one by enabling amorphous phase formation.     

Novel polyamides with pendant p-phenylenediamine and α-/β-substituted naphthalene: synthesis,characteristics, and effects of substitution sites on electro-switchable optical behaviors

Recently, electro-switchable optical materials have attracted much attention for their promising applications in optoelectronic devices and biological analysis. The structures of active optical moieties are dominant for the resulting performance, which raises the requirement of studying their structure-property relationship. In this study, two p-phenylenediamine–based polyamides (α-HPA and β-HPA) containing α-/β-substituted pendant naphthalene were designed and synthesized to investigate the effect of two substitution sites of naphthalene on their thermal, optical, electrochemical, electrochromic, and electrofluorochromic behaviors. Quantum chemical calculations were carried out to help the analysis of the experimental results. The as-prepared polyamides both exhibited excellent solubility, thermal stabilities (no weight loss before 300 °C in air), and optical switching stability (500 cycles). Because of the more twisted conformation and stronger charge transfer effect between diphenylamine and α-substituted naphthalene, the α-HPA exhibited higher glass transition temperature, higher coloration efficiency, weaker fluorescence quantum efficiency, red-shifted emission wavelength, and rapider switching speed than the β-HPA. This study not only presents a deep understanding of substitution sites of fluorophores on the electro-switchable optical behaviors but also demonstrates the tailorability of the electrochromic/electrofluorochromic characteristics through fine structure adjustment, paving a pathway for further development of high-performance electrochromic/electrofluorochromic materials.     

纳米纤维素/聚3,4-乙撑二氧噻吩复合薄膜的制备及电致变色性能

以棉浆粕为原料,采用硫酸溶胀结合超声波处理的方法制备了纳米纤维素(NC).在纳米纤维素的水分散液中加入3,4-乙撑二氧噻吩单体,以过硫酸铵为氧化剂,采用原位化学氧化法制得了纳米纤维素/聚3,4-乙撑二氧噻吩(NC/PEDOT)纳米复合物.对NC和NC/PEDOT复合物进行扫描电镜、透射电镜和红外光谱分析.将纳米复合物的水分散液滴涂在氧化铟锡(ITO)玻璃表面形成复合薄膜,考察不同纳米纤维素含量对NC/PEDOT复合薄膜电致变色性能的影响.结果表明,NC呈棒状,平均直径为20 nm,长度为100~300nm;NC/PEDOT复合物中PEDOT均匀包覆在NC表面形成核壳结构,平均直径为30 nm;复合薄膜中当NC含量为60%时,其电致变色性能最好,具有最高的对比度(24.4%),最短的响应时间(1 s),最高的着色效率(51.8 cm~2/C).     

Conjugated oligomers with thiophene and indole moieties: Synthesis,photoluminescence and electrochromic performances

Two series of thiophene oligomers and terthiophene oligomers consisting of both thiophene and indole moieties have been synthesized. They have same excitation-dependent photoluminescence characteristics, but different bandgaps and absorption behaviors, which relates to the number and denseness of indoles in the conjugated oligomers and the length of alkyl chains on indole moiety due to varied the π-π stacking interaction of conjugated structures in the as-prepared oligomers. A simple electrochromic device based on such a conjugated oligomer displays a novel four-color electrochromism from red to yellow, green and puce with the increased potential and possesses good environmental and redox stability. Such conjugated oligomer also exhibits high sensitivity and selectivity for Zn²⁺ detection.     

Effects of Supporting Electrolytes on Spectroelectrochemical and Electrochromic Properties of Polyaniline‐poly(styrene sulfonic acid) and Poly(ethylenedioxythiophene)‐poly(styrene sulfonic acid)‐based Electrochromic Device

Electrochromic devices are fabricated by using polyaniline (PANI) doped with poly(styrene sulfonic acid) (PSS) as coloring electrodes, poly(ethylenedioxythiophene)‐poly(styrene sulfonic acid) (PEDOT‐PSS) as complementary electrodes, and hybrid polymer electrolytes as gel electrolytes. The device based on LiClO₄‐based electrolyte (weight ratio of PMMA:PC:LiClO₄ = 0.7:1.1:0.3) shows the highest optical contrast and coloration efficiency (333 cm²/C) after 1200 cycles in these devices, and the color changes from pale yellow (?0.5 V) to dark blue (+2.5 V). The spectroelectrochemical and electrochromic switching properties of electrochromic devices are investigated, the maximum optical contrast (ΔT%) of electrochromic device for ITO|PANI‐PSS‖PMMA‐PC‐LiClO₄‐SiO₂‖PEDOT‐PSS|ITO are 31.5% at 640 nm, and electrochromic device based on LiClO₄‐based electrolyte with SiO₂ shows faster response time than that based on LiClO₄‐based electrolyte without SiO₂.     

The effect of temperature on the preparation of electrochromic nickel oxide by an electroless method

The advantages of nickel oxide as an electrochromic material are due to its good contrast of transmittance and its suitable use as a secondary electrochrome. Compared to other methods of depositing eletrochromic nickel oxide, coating nickel oxide by electroless is simple and easy to scale-up for industrial application. This study presents the preparation of nickel oxide film on an ITO substrate by an electroless method and oxidizing it with heat treatment. The influence of oxidizing temperature in heat treatment procedures is notable. The morphology of the film was analyzed by a scanning electron microscope (SEM) and X-ray diffraction (XRD). Heat temperature at 380 °C obtained optimal of electrochromic properties. The transmittance difference (ΔT) of the film at 630 nm was maintained at 69%, and the amount of transferred charge during cyclic voltammetry was approximately 0.8 mC/cm² after 1000 cycles of redox, which was operated between −1.5 and +1.5 V potential step. The degradation of the film was decreased by increasing the oxidizing temperature. The evidences showed electrochromic abilities of nickel oxide were affected by heat-treatment procedures. All these analyses provided a novel method for preparing the electrochromic nickel oxide in a low-cost way.     

Polypyrrole films electropolymerized from ionic liquids and in a traditional liquid electrolyte: A comparison of morphology and electro-optical properties

Polypyrrole (pPy) films have been formed by electropolymerization from a conventional media: lithium triflate in acetonitrile and in room temperature ionic liquids: 1-ethyl-3-methyl imidazolium bis(perfluoroethanesulfonyl)imide (EMIPFSI) and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMITF). The well ordered nodular morphology of the pPy film grown in EMIPFSI with significantly low roughness endows these films with superior redox activity and electro-optical properties. Ambient temperature dc conductivities of 43, 15 and 13 S cm⁻¹, for films grown in EMIPFSI, EMITF and control solutions have seen obtained. The well-organized particulate morphology of the pPy film grown in EMIPFSI seems to be responsible for its enhanced conductivity, as also better interfacial charge transfer capabilities as compared to their counterparts derived. Under an external bias of ±2.2 V, the sluggish switching kinetics shown by the films under scrutiny presumably are due to the (i) resistive barriers formed at the two interfaces of the pPy electrode (ii) a plausible passivation layer on the solution side of the film during electrochemical cycling. This demonstrates the need to further improve the interfacial properties of pPy so as to obtain a consistent and stable electrochromic response.     

无机-无机复合电致变色材料的研究进展

在外加电压的作用下,电致变色材料的光学性能（颜色、透光率等）能够可控制、可逆地变化,在节能减排领域有重要应用前景。随着相关研究的不断创新、深入和拓展,单一组分的电致变色材料因受到其自身结构和性能的限制,不能表现出人们所期望的电致变色性能,并且在结构和性能上不具有可设计和调控性,因而越来越无法满足实际应用的需求。与非复合电致变色材料相比较,复合型材料在这方面具有明显的优势,其优势体现在通过合理的材料设计,借助复合材料各组分的协调作用,充分激发各组分的优点,克服各自的缺点,可以获得结构和性能优异的电致变色材料。因此,近年来越来越多的研究聚焦于复合型电致变色材料。目前已开展研究的复合型电致变色材料的种类很多,根据复合组分是无机材料还是有机材料来对复合型电致变色材料分类的话主要可分为无机-无机复合、无机-有机复合和有机-有机复合3大类。相比有机电致变色材料,无机电致变色材料在材料成分控制、机械性能、光调制、使用稳定性、寿命等方面优势显著,因此,单一组分的和复合型的无机电致变色材料始终是本领域研究的重要方向。因此,本文致力于近年来无机-无机复合电致变色材料、器件和电解质的研究现状和未来的发展动态,对其研究进展、所存在的问题和发展趋势进行了归纳总结,为复合型电致变色材料的进一步研发和应用提供依据。     

Assembly of tungsten oxide nanobundles and their electrochromic properties

Lenticular W₁₈O₄₉ nanobundles composed of ultra-thin nanowires with diameters of 5-10 nm have been synthesized through a simple solvothermal method with hexachloride as precursor and mixed cyclohexanol and ethanol as solvent. Electrochromic films were prepared by assembling the W₁₈O₄₉ nanobundle suspension onto tin-doped indium oxide (ITO) coated glass. Results showed that self-assembly of the W₁₈O₄₉ nanobundles was strongly influenced by the solvents employed to disperse the nanobundles. The W₁₈O₄₉ nanobundles coated films exhibited excellent electrochromic stability and reversibility. The W₁₈O₄₉ nanobundle films also showed much higher charge-insertion density compared with the WO₃ nanorod film, which may be due to the ultrathin feature of single nanowires constituting the nanobundles, unique oxygen vacancies of monoclinic W₁₈O₄₉, and the highly ordered assembly of the nanobundles.