Electrochromism refers to the phenomenon where the optical properties of materials (such as reflectance, transmittance, absorption rate, etc.) undergo stable and reversible color changes under the influence of an external electric field. In appearance, it is manifested as reversible changes in color and transparency. Materials with electrochromic properties are called electrochromic materials. Electrochromic materials are a new type of functional material and have extensive applications in information, electronics, energy, construction, and national defense, among other fields. Devices made of electrochromic materials are called electrochromic devices.
Material requirements
Electrochromic glass materials can undergo reversible color changes under the action of a relatively low applied driving voltage or current, causing reversible changes in the valence state and composition of the material, and altering or maintaining the optical properties of the material. At the same time, electrochromic materials also need to have excellent ionic conductivity, high contrast, color-changing efficiency, and cycle period and other electrochromic properties. Electrochromic materials are classified into inorganic electrochromic materials and organic electrochromic materials [2] The typical representative of electrochromic materials without electrical components is tungsten trioxide. Currently, electrochromic devices with WO3 as the functional material have been industrialized. The organic electrochromic materials mainly include polythiophenes and their derivatives, rhodophenes, tetrasulfovalene, and metal phthalocyanine compounds, etc. Electrochromic materials with purple-like substances as functional materials have been put into practical application. In practical applications, especially in the preparation of electrochromic devices, electrochromic materials generally should meet the following requirements:
(1) It has good electrochemical REDOX reversibility;
(2) Rapid color-changing response;
(3) Reversible color change;
(4) High sensitivity to color changes;
(5) It has a relatively high cycle life;
(6) It has a certain storage and memory function;
(7) Stable chemical properties.
Product application
Electrochromic glass has the adjustability of light absorption and transmission under the action of an electric field. It can selectively absorb or reflect external thermal radiation and internal heat diffusion, reducing the large amount of energy that office buildings and residential buildings must consume to keep cool in summer and warm in winter. At the same time, it serves to improve the degree of natural light and prevent peeping. Electrochromic materials possess bistable properties. Electrochromic displays made of electrochromic materials not only do not require backlights but also, after displaying static images, as long as the displayed content remains unchanged, they will not consume electricity, achieving the goal of energy conservation. Electrochromic displays have advantages such as no blind spots and high contrast compared with other displays. The automatic anti-glare rearview mirror made of electrochromic materials can adjust the intensity of the reflected light according to the intensity of the external light through an electronic sensing system, achieving the effect of anti-glare and making driving safer. Electrochromic smart glass can adjust the light intensity inside cars and aircraft at a relatively low voltage (2-5V) and power, making the journey more comfortable. At present, electrochromic tinted light glass has been applied in some high-end cars and aircraft. After half a century of development, electrochromism has achieved many effective results and has been put into use in some fields. With the continuous development of science and technology, electrochromic materials and their devices are bound to play a more important role.
