Recently, the team of researchers Cao Xun of the Shanghai Institute of Ceramics of the Chinese Academy of Sciences cooperated with researcher Sun Yiyang, Professor Luo Hongjie of Shanghai University, Professor John Bell of Queensland University of Technology in Australia, and China National Building Materials Bengbu Glass Industrial Design and Research Institute to develop electrochromic devices with fast response speed and high on/fading contrast. The research results, titled All-solid-state proton-based tandem structures for fast-switching electrochromic devices, were published in Nature Electronic on January 24, 2022.
Researcher Cao Xun told Fruit Shell Hard Technology: "Our research team first proposed the use of proton relay transmission to achieve a fast switching of high on/fading ratio in WO3 electrochromic materials from the two dimensions of experiment and theory, and successfully prepared an ultra-fast response of all-solid-state electrochromic devices, breaking through the application limitations caused by slow response speed and greatly expanding the application field." ”
Preparation of large-area and flexible electrochromic devices | Photo courtesy of Shao Zewei
All-solid-state electrochromic devices work by applying voltage to the device to regulate the transmittance of solar radiation, which can be used to make smart windows. Electrochromic refers to the phenomenon of stable and reversible color changes in the optical properties of materials (reflectivity, transmittance, absorption rate, etc.) under the action of an applied electric field, which is manifested as a reversible change in color and transparency in appearance.
Electrochromic devices prepared by electrochromic materials can be widely used in the field of energy-saving windows and displays. Especially in the field of display, the slow response speed seriously restricts its application in electronic devices. This operation reduces the response time of the device to less than 1 s (0.7 s) while increasing the device's on/fading contrast, significantly reducing power dissipation as an electronic device, bringing it closer to the refresh rate of the display device, and accelerating its application process.
"Electrochromic core application scenarios, in addition to buildings, automobiles, etc. windows, is some low-power steady-state display devices, the current display field is not used electrochromic, on the one hand, electrochromic discoloration is generally a monostable device, bistable is the future research direction, the realization of bistable can be applied in many display areas, such as supermarket electronic price display code, etc.; on the other hand, the change of color also makes electrochromic in some consumer electronics such as mobile phones to obtain applications, Personalized incoming calls, etc. can be realized. Researcher Cao Xun explained.
The electrochromic device developed by the research team consists of five layers of material, including two layers of transparent conductive electrode (ITO), tungsten oxide, organic SUBSTANCE PEDOT:PSS and Na+ ion counter electrode layer. Tungsten oxide (WO3) is currently the most widely used electrochromic material due to its excellent properties. The electrochromic process of WO3 is mainly based on the reversible valence of W elements and the reversible embedding and shedding of cations (H+, Li+, Na+, Al3+, etc.). Among them, embedding and shedding cations are the key factors affecting the coloring speed and cycle stability of the material. Among the many cations, protons (H+) have a smaller ion radius and faster migration rate than other cations, and have obvious advantages in the embedding and shedding process of electrochromic discoloration. However, protons are often present in liquid electrolytes and do not integrate well in solid-state electrochromic devices.
In this result, Cao Xun's team for the first time introduced organic matter (PEDOT:PSS) that can achieve rapid proton migration as a solid-state proton source, and designed an electrochromic layer in series with the WO3 electrochromic layer. The researchers found that it was still effectively on/fading at short pulse stimulation of 5/8 s. However, this process of onset/fading is limited by a limited supply of protons, which varies by only about 15% and does not yet capture the full performance of the device. Based on this, the work innovatively proposes to insert a layer of Na+ ion source to promote the efficient release of H+. In addition, driven by further voltages, more Na+ enters the PEDOT:PSS layer, and the degree of shading continues to deepen, resulting in higher shading contrast pairs. First-principles computation also provides theoretical evidence for the above proton relay migration mechanism.
Schematic diagram of the structure of a relayed proton transport electrochromic device | Photo courtesy of Shao Zewei
The researchers further prepared an all-solid-state electrochromic device and evaluated the overall performance, and found that the electrochromic device based on this structure had high on/fading contrast (up to 90% at 650 nm) during the coloring process, ultra-fast response speed (coloring to 90% within 0.7s, fading to 65% within 0.9 s, fading to 90% within 7.1s), good coloring efficiency (109 cm2C-1 at 670 nm) and excellent cycle stability (after 3,000 cycles, the ignition// Fading contrast is reduced by less than 10%). In addition, the researchers extended the design to large-area all-solid-state electrochromic devices (30×40 cm2) and flexible devices (10×10 cm2).
For the further improvement of the performance of electrochromic devices, Researcher Cao Xun introduced: "Electrochromic discoloration will improve the uniformity of color change in the future, which will have great prospects in the fields of construction or car windows. In addition, the polychromatic color of electrochromacy is also an important development direction, which can meet people's different application needs. ”
The performance characterization results of the new electrochromic devices | Photo courtesy of Shao Zewei
bibliography
[1] Shao, Z., Huang, A., Ming, C. et al. All-solid-state proton-based tandem structures for fast-switching electrochromic devices. Nat Electron 5, 45–52 (2022). https://doi.org/10.1038/s41928-021-00697-4
Author: Shao Zewei
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Typography: Yin Ningliu
Research team
Corresponding author Cao Xun: Researcher of Shanghai Institute of Ceramics, Chinese Academy of Sciences, doctoral supervisor, deputy director of the Center for Ancient Ceramics and Industrial Ceramics, leader of the "Solar Thermal Regulation Intelligent Materials Research Group", Shanghai Pujiang Talent. Graduated from Jilin University in 2004 with a bachelor's degree, graduated from the Shanghai Institute of Ceramics, Chinese Academy of Sciences in 2010, majoring in materials physics and chemistry, obtained a doctorate degree in engineering, stayed in the institute after graduation as an assistant researcher, associate researcher, began to work in the University of California, Berkeley and Lorenz National Laboratory in 2015 to engage in research on functional thin film materials and devices, at the end of 2016, after returning to China, has served as the deputy leader of the research group, team leader, researcher. His research interests mainly include solar thermal control materials and components, new energy-saving materials and coating development. He won the final prize of the first "First Cup" Future Technology Innovation Competition of the Chinese Academy of Sciences (ranked first), and published 60 SCI papers in the field of CSP regulatory materials and devices; the results have been published by a variety of internationally renowned journals (such as: Nat. Nanotechnol., Adv. Mater., Rep. Prog. Phys. et al.) cited more than 2600 times, H factor 29. For nearly five years, with the first/corresponding author in Nat. Electron., Matter (2 articles), Adv. Energy Mater., Nano Energy (2 articles), Acc Mater. Res., NPG Asia Mater., Laser Photonics & Rev. (2), J. Mater. Chem. He has published more than 50 papers in international core journals such as A (2 papers). He was invited to write 4 English books related to solar thermal regulatory materials, and currently serves as a young editorial board member of Materials Research Letters, Advances in Manufacturing, and Journal of Inorganic Materials. The first/main inventor has applied for 30 patents and has been authorized 17 times; he has been invited to make invited reports at academic forums such as the International/Domestic Electrochromic Materials Conference and the International Special Ceramics Conference. As the person in charge, he has presided over more than 20 projects such as the National Key R&D Program, the National Natural Science Foundation of China (3 projects), the pre-research support of the Chinese Academy of Sciences, the international cooperation of the Chinese Academy of Sciences, JPPT, and GF innovation.
Group photo of Cao Xun's team of researchers | Photo courtesy of Shao Zewei
First author Shao Zewei: Received his bachelor's degree from the Department of Materials Science and Engineering, University of Science and Technology of China in 2016, and his Ph.D. from the Shanghai Institute of Ceramics, Chinese Academy of Sciences in 2021, under the supervision of researchers Jin Pingshi and Cao Xun. Since 2021, he has been engaged in postdoctoral research in the team of professors at The Hangzhou International Science and Technology Innovation Center of Zhejiang University, mainly in the fields of functional oxides and wide bandgap semiconductors, and is committed to the design and construction of high-performance oxide interfaces.
Thesis information
Published the journal Nature Electronics
Published January 24, 2022
文章标题All-solid-state proton-based tandem structures for fast-switching electrochromic devices
(DOI:https://doi.org/10.1038/s41928-021-00697-4)
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