【作者】 张俊；

【导师】 涂江平；

【作者基本信息】 浙江大学 ， 材料学， 2012， 博士

【摘要】 本论文以W03为主要研究对象,采用多孔化、纳米阵列化、有机复合化等手段对其进行电致变色性能优化研究,主要目的是提高其电致变色光谱调制幅度,变色响应速度以及变色效率,并探索了W03薄膜在红外波段的电致变色性能,组装了基于WO3和NiO互补变色机制的凝胶型全固态原型器件。利用阳极氧化法在溅射金属钨层的ITO玻璃表面形成了W03多孔薄膜,相比于致密态的WO3薄膜,阳极氧化法获得的W03多孔薄膜具有更加优越的电致变色性能,包括更快的响应速度和更大的可见光调制幅度。利用PS球模板法在ITO玻璃表面制备了大孔WO3阵列薄膜。其光谱调制幅度、变色速度等有了较大的提高,同时大孔阵列薄膜的循环性能没有明显下降。多孔性WO3薄膜为电化学反应提供了更多的活性界面,可缩短离子扩散路径,增强电极反应动力学。分别用水热氧化法和水热合成法制备了WO3纳米树等级结构阵列薄膜和纳米线阵列薄膜。用水热氧化法直接在金属钨片上生长WO3纳米树等级阵列薄膜,薄膜具有六方晶系,并在500℃以下热处理可保持晶体结构不变。六方结构W03中存在的六角形和三角形离子通道,有利于离子的扩散；纳米树等级结构既有开放性的多孔表面与电解液充分接触,又与导电基底紧密连接,因此表现出了优异的电致变色性能。400℃热处理的薄膜的反射率调制范围达30%(500 nm处),变色效率为43.6 cm2C-1。用水热合成法在FTO玻璃表面沉积了WO3薄膜,通过调整结构控制剂的浓度,可获得不同形貌和结构的WO3薄膜。在优化的条件下,可以制备具有纳米线阵列形貌的W03薄膜。相比于不加硫酸铵所制成的“微米砖”薄膜,纳米线阵列薄膜具有更佳的电致变色性能。WO3纳米线阵列薄膜在633 nm的透过率调制范围为58%,电致变色效率高达102.8 cm2 C-1。,而“微米砖”薄膜分别只有45%和24.5 cm2 C-1。WO3纳米线阵列薄膜同时表现出了很快的变色响应速度,着色时间7.6 s,褪色时间4.2 s。电化学阻抗分析结果表明薄膜具有更高的电化学活性和电极反应动力。以过氧化钨酸(PTA)作为掺杂剂,用一种简易的化学氧化聚合法一步合成了PANI-WO3复合薄膜,这些薄膜具有由纳米短棒组成的粗糙表面,WO3相被均匀地复合在PANI网络中。由于W03和PANI的着色与褪色所在的电压范围并不完全重叠,使复合薄膜具有了双向的电致变色效应。得益于WO3和PANI两者本身所具有的优点以及施主-受主体系的形成,有机／无机复合薄膜具有较好的电致变色性能,如更快的变色速度和更长的循环寿命。利用直流磁控溅射法制备了WO3薄膜，并研究了基底温度对薄膜结晶性能进而在红外波段的电致变色性能的影响。W03薄膜红外电致变色性能随基底温度的升高而增强,在250℃时,薄膜在8-12μm的中红外大气窗口具有35%调制幅度,在9μm处的变色效率达18.5 cm2C-1。但是过高的基底温度(300℃)导致薄膜不能很好地嵌入离子,因而红外波段的电致变色性能反而下降。用磁控溅射制备的WO3薄膜和化学浴法制备的NiO薄膜为电致变色层和离子存储层(互补变色层),用含Li’凝胶型聚合物为电解质层,设计并组装了电致变色原型器件。该互补型电致变色器件表现出优越的性能,在550 nm处的透过率调制幅度达55%,变色效率达87 cm2 C-1,并具有很好的循环稳定性,循环1600次无明显衰减。更多还原

【Abstract】 In this dissertation, tungsten trioxide (WO3) based thin films for electrochromic applications are developed using various approaches including sputtering, anodic oxidation, hydrothermal method, templating method, hybridization, etc. The main purpose is to improve the electrochromic properties of WO3 based materials such as spectrum modulation, switching speed and coloration efficiency. The electrochromic effect of WO3 thin films in infrared band is also investigated. Finally, an all-solid-state electrochromic device based on NiO/WO3 complementary structure and solid hybrid polyelectrolyte is fabricated.Self-organized macroporous WO3 films were grown by an anodic oxidation in a NaF electrolyte from a DC-sputtered tungsten layer on ITO glass. Well-structured films adhere to the entire surface under optimized experimental conditions. The as-anodized films show an amorphous structure and are poorly transparent. After annealing, the films adopt an orthorhombic structure and become transparent. The anodized WO3 films on ITO glass with macroporous structure exhibit excellent electrochromic properties, including faster switching speed and larger color contrast. WO3 microbowl array films have been electrodeposited on ITO glasses using PS spheres as template. The films show a connected network of monodispersed pores with average size of 600 nm after the template is removed. Comparing to dense films prepared without PS template for the same deposition time, the porous WO3 films deposited with PS template show enhanced electrochromic properties, i.e. high switching speed and fast coloration efficiency. Especially for the WO3 microbowl array film deposited for 300 s, a coloration efficiency as high as 68 cm2C-1, and fast coloration (bleaching) speeds of 3.6 s (1.0 s) are obtained. Mean while the cyclic stability has no significant difference between the WO3 films prepared with and without PS template.WO3 nanotree films were prepared by hydrothermal oxidation of W substrate. The film thickness can be controlled by adjusting the hydrothermal duration and a 550 nm-thick nanotree film was obtained after hydrothermal process for 5 h. The as-prepared film was of hexagonal structure and kept its crystal structure until it was annealed up to 500℃. The nanotree film annealed at 400℃exhibits remarkable electrochromic properties with an optical reflectance modulation of 30% at 500 nm. The coloration efficiency value as high as 43.6 cm2 C-1 is achieved for this film. This is due to the porous structure of nanotree film and its hexagonal and trigonal tunnels of h-WO3, into which Li+can be intercalated and deintercalated readily. Hexagonal WO3 nanowire array film was obtained using a template-free hydrothermal method by adding ammonium sulfate as capping agent. The WO3 nanowires grown vertically on FTO-coated glass substrate are woven together at the surface of the film, forming well-aligned arrays at the bottom part and a porous surface morphology. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) reveal that each nanowire is a hexagonal single crystal and the long axis of it oriented toward [0001] direction. Due to the highly porous surface, good contact with conductive substrate and large tunnels of hexagonal structured WO3, fast switching speed of 7.6 and 4.2 s for coloration and bleaching, respectively, and high coloration efficiency of 102.8 cm2 C-1 are achieved for the WO3 nanowire array film.Nanostructured polyaniline (PANI)-WO3 hybrid thin films were synthesized via a molecular assembling route in a solution of aniline using peroxotungstic acid (PTA) as the dopant and ammonium persulfate as the oxidant. The films show a porous morphology with nanorod arrays on the surface, and WO3 is uniformly incorporated into the polymer network. Electrochemical and electrochromic tests including cyclic voltammetry, chronoamperometry and corresponding in situ transmittance of PANI-WO3 hybrid films comparing with neat PANI film and sol-gel WO3 film were conducted in 0.5 M sulfuric acid solution. The hybrid films, being a dual electrochromic material, varied from royal purple to green, pale yellow and finally dark blue as the applied potential was scanned from 0.8 V to-0.5 V. Compared to sulfate doped PANI film, the high colouration efficiency and comparable durability are obtained in the PANI-WO3 hybrid films. The PANI-WO3 hybrid films also show faster switching speed and better durability than WO3 film. The enhanced electrochromic properties such as faster switching speed and better durability are mainly attributed to the combining of advantages of both materials and the formation of the donor-acceptor system.WO3 films were deposited by reactive dc magnetron sputtering at different substrate temperatures. With the increasing of the deposition temperature, the diffusion coefficient of H+ ions in the WO3 films decrease. The infrared reflectance modulation and color efficiency first increase and then decrease with the deposition temperature, and maximum values of 40% and 18.5 cm2 C-1, respectively, are achieved at 250℃and 9μm. The WO3 films with reflectance modulation (higher than 30%) in infrared band can be fabricated into devices, which have considerable applications in thermal control and infrared camouflage. An all-solid-state electrochromic device based on NiO/WO3 complementary structure and solid polyelectrolyte was manufactured for modulating the optical transmittance. The device consists of WO3 film as the main electrochromic layer, single-phase hybrid polyelectrolyte as the Li+ ion conductor layer, and NiO film as the counter electrochromic layer. Indium tin oxide (ITO)-coated glass was used as substrate and ITO film act as the transparent conductive electrodes. The effective area of the device is 5×5 cm2. The device showed an optical modulation of 55% at 550 nm and achieved a coloration efficiency of 87 cm2 C-1. The response time of the device is found to be about 10 s for coloring step and 20 s for bleaching step. The electrochromic mechanism in the NiO/WO3 complementary structure with Li+ion insertion and extraction was investigated by means of cyclic voltammograms (CV) and X-ray photoelectron spectroscopy (XPS).更多还原