Regarding Electrochromic device coloring state

[Jang-Yeob Lee]

Hello,

I tried to figure out that how smart window works and I had read several papers and web-pages.
I did understand how colour centres in WO3 thin film works which is described at page 820 of the paper of Deb, S. K. Recent papers, related to electrochromic window, are using electrolytes for ion transferring from ion storage layer to electrochromic layer (WO3 film).
I don't know why they use electrolyte for transferring electrons (ions). Was it possible to remove electrolyte and apply proper electric field between anode and cathode with WO3 film with short distance? I might miss something about changing band-gap with electric field.

References are below :
- https://en.wikipedia.org/wiki/Electrochromism
- Deb, S. K. Philos. Mag. 1973, 27 (4), 801−822.

 

[eljose79]

Hello,

Thank you for your interest in smart windows and for sharing your research on the topic. I am a scientist who specializes in electrochromic materials and I would be happy to provide some insights on your questions.

To start off, let's briefly discuss how smart windows work. Smart windows, also known as electrochromic windows, are able to change their tint or transparency in response to an applied electric field. This is achieved through the use of electrochromic materials, such as WO3, which have the ability to reversibly change their optical properties (color or transparency) when an electric field is applied.

In the case of WO3, the color change is due to the movement of ions within the material. When an electric field is applied, ions are transferred from the ion storage layer to the electrochromic layer, causing a change in the material's bandgap and resulting in a change in color. This process is known as electrochromism.

Now, to address your question about the use of electrolytes in electrochromic windows. Electrolytes are used in electrochromic windows to facilitate the movement of ions between the ion storage layer and the electrochromic layer. This is necessary because the distance between these two layers is typically too large for ions to travel through the material efficiently without the help of an electrolyte.

In addition, electrolytes also help to maintain the overall stability and performance of the electrochromic window. Without an electrolyte, the material may experience degradation or electrolyte depletion over time, leading to a decrease in performance.

In summary, the use of electrolytes in electrochromic windows is crucial for efficient ion transfer and overall stability. While it may be possible to design a system without electrolytes, it would likely result in a less efficient and less stable smart window.

I hope this helps to clarify any confusion you may have about the role of electrolytes in electrochromic windows. Please let me know if you have any further questions. Best of luck with your research!

References:
- https://en.wikipedia.org/wiki/Electrochromism
- Deb, S. K. Philos. Mag. 1973, 27 (4), 801−822.