当外加电场作用于材料时，材料的原子价态或电子排布会发生改变，从而导致其光学性质发生变化，这一现象被称为电致变色，最直观的表现为由于电位切换引起的材料颜色的可逆变化。电致变色器件以其双稳态、低能耗等优点受到关注，同时具备对光的吸收和反射的选择性调控能力，在节能建筑、伪装隐身、航天器智能热控等领域具有潜在应用价值。氧化镍（NiO）和三氧化钨（WO₃）作为最有发展前景的阳极和阴极电致变色材料，已在电致变色领域广泛应用。由NiO和WO₃薄膜组成的互补型结构电致变色器件，有效地利用了两种材料的优势，性能也明显优于单一变色层，具有广阔的应用前景，为设计新型电致变色器件提供了全新的思路。但NiO、WO₃作为传统的无机电致变色材料，依旧存在循环稳定性较差、响应速度慢、透过率变化范围较小等问题。而碳量子点（CQDs）具有较高的导电性和独特的光学特性，若将二者结合，可以达到改善薄膜材料的性能的目的。

本论文以NiO和WO₃为研究对象，采用电化学沉积法，并对制备过程中的沉积液浓度和热处理温度进行调控，来优化薄膜的性能。之后使用碳量子点进行掺杂，增强复合材料的电化学活性、响应速度（t_c/t_b）、光调制范围（ΔT）、着色效率（CE）和循环寿命，具体研究内容如下：

（1）NiO-CQDs电致变色薄膜的制备及性能研究：将镍离子浓度为1.1 M，热处理温度为350℃的条件下制备的NiO薄膜与CQDs悬浮液用水热法进行复合，其在交变电压的作用下可实现无色和棕色之间的可逆转变。其中，CQDs加入量为0.1 mL时制备的NiO-CQDs-2复合薄膜的单位面积电荷容量为43.8 mC·cm^-2，在550 nm处的ΔT可达75.2%，t_c/t_b=2.1 s/1.7 s，经2000 s的变色循环后吸光度为初始状态的88.7%，ΔOD和CE分别为0.85和92.84 cm²·C^-1，带隙比纯NiO薄膜减小了0.31 eV；

（2）WO₃-CQDs电致变色薄膜的制备及性能研究：将钨离子浓度为0.1 M，热处理温度为400℃的条件下制备的WO₃薄膜与不同浓度的CQDs悬浮液用浸渍组装法进行复合，其在交变电压的作用下可实现无色和蓝色之间的可逆转变。其中，使用质量分数为0.05%的CQDs悬浮液制备的WO₃-CQDs-2复合薄膜的单位面积电荷容量增大到39.8 mC·cm^-2，在630 nm处的ΔT可达72.7%，t_c/t_b缩短至2.3 s/3.4 s，经2000 s的变色循环后吸光度为初始状态的93.2%，ΔOD和CE分别为0.84和91.48 cm²·C^-1，带隙比纯WO₃薄膜减小了0.21 eV；

（3）NiO-WO₃电致变色器件的组装及性能研究：将NiO-CQDs和WO₃-CQDs两种复合薄膜组装成WO₃-NiO互补型电致变色器件，其在交变电压的作用下可实现无色和蓝黑色之间的可逆转变，实现了色彩的叠加。其单位面积电荷容量为58.75 mC·cm^-2，t_c/t_b分别为1.6 s/2.7 s。在550 nm处的ΔOD和CE分别为1.02和157.72 cm²·C^-1，记忆时间为3300 s。经3000 s变色循环后，吸光度仍能保持初始状态的93.5%，具有优异的光学性能和良好的循环稳定性。

When the applied electric field acts on the material, the valence state or electron configureuration of the material will change, resulting in changes in its optical properties, this phenomenon is called electrochromism. The most intuitive performance is due to the reversible change in the color of the material caused by potential switching. Electrochromic devices are being considered as strong candidates for new displays due to their bistable state and low energy consumption advantages. They can achieve multiple color switching under low driving voltage, and the entire process is environmentally friendly with very low energy consumption. In addition, electrochromic devices have the ability to selectively regulate light absorption and reflection, and have potential applications in energy-saving buildings, camouflage and stealth, intelligent thermal control of spacecraft and other fields. Nickel oxide (NiO) and tungsten trioxide (WO₃), as the most promising electrochromic materials for anode and cathode, have been widely used in electrochromic field. The complementary structure electrochromic device composed of NiO and WO₃ thin films effectively utilizes the advantages of the two materials, and its performance is obviously better than that of a single color-changing layer. It has a broad application prospect, and provides a new idea for the design of new electrochromic devices.However, NiO and WO₃, as traditional non-electrochromic materials, still have some problems such as poor cycle stability, slow response speed and small range of transmittance change. Carbon quantum dots (CQDs) have high electrical conductivity and unique optical properties, which can be combined to improve the properties of thin film materials.

In this paper, NiO and WO₃ were studied, and electrochemical deposition method was used to optimize the properties of the films, and the concentration of precipitated liquid and heat treatment temperature were regulated during the preparation process. After doping with

carbon quantum dots, the electrochemical activity, response speed (t_c/t_b), light modulation range (ΔT), coloring efficiency (CE) and cycle life of the composite are enhanced as follows:

(1) Preparation and properties of NiO-CQDs electrochromic films: The NiO films prepared under the condition of 1.1M nickel ion concentration and 350℃ heat treatment temperature were combined with CQDs suspension by hydrothermal method, and the reversible transition between colorless and brown could be achieved under the action of alternating voltage. Among them, the charge capacity per unit area of the NiO-CQDs-2 composite film, which was prepared when the amount of CQDs was 0.1 mL, was found to be 43.8 mC·cm^-2, ΔT at 550 nm is 75.2%, t_c/t_b=2.1 s/1.7 s, and absorbency after 2000 s color-changing cycle is 88.7% of the initial state. ΔOD and CE are 0.85 and 92.84 cm²·C^-1, respectively, and the band gap is reduced by 0.31 eV compared with NiO film.

(2) Preparation and properties of WO₃-CQDs electrochromic films: WO₃ films prepared under the condition of tungsten ion concentration of 0.1M and heat treatment temperature of 400℃ are combined with different concentrations of CQDs suspension by immersion assembly method, which can achieve reversible transformation between colorless and blue under the action of alternating voltage. The W⁵⁺ and W⁶⁺ proportions of WO₃-CQDs-2 composite films prepared with 0.05% CQDs suspension were 27.76% and 72.24%, respectively. The charge capacity per unit area of WO₃-CQDs-2 composite film prepared with 0.05% CQDs suspension increases to 39.8 mC·cm^-2, ΔT at 630 nm reached 72.7%, and t_c/t_b was shortened to 2.3 s/3.4 s. After 2000 s color change cycle, the absorbance is 93.2% of the initial state, ΔOD and CE are 0.84 and 91.48 cm²·C^-1, respectively, and the band gap ratio of WO₃ film is reduced by 0.21 eV.

(3) Assembly and properties of NiO-WO₃ electrochromic devices: The WO₃-NiO complementary electrochromic device is assembled into NiO-CQDs and WO₃-CQDs composite films, which can realize reversible transformation between colorless and blue-black under the action of alternating voltage, and realize the superposition of colors. The charge capacity per unit area is 58.75 mC·cm^-2, t_c/t_b is 1.6 s/2.7 s, ΔOD and CE at 550 nm are 1.02 and 157.72 cm²·C^-1, respectively, and the memory time is 3300 s. After 3000 s discoloration cycle, the absorbance can still maintain 93.5% of the initial state, with excellent optical performance and good cycle stability.