Featured Research

from universities, journals, and other organizations

Smart windows: Understanding how hydration affects color-changing windows can boost efficiency

Date:
November 20, 2013
Source:
The Agency for Science, Technology and Research (A*STAR)
Summary:
Electrochromic materials dynamically alter how they transmit light in response to an applied electrical signal. Engineers are currently working to turn these compounds into 'smart windows' for buildings that change from transparent to colored states at the flick of a switch. Such devices can help to prevent heat loss and maximize the amount of natural light passing through windows.

‘Smart’ films that change color on demand can be fabricated more efficiently, thanks to a new mechanistic study.
Credit: Copyright : 2013 A*STAR Institute of Materials Research and Engineering

Electrochromic materials dynamically alter how they transmit light in response to an applied electrical signal. Engineers are currently working to turn these compounds into 'smart windows' for buildings that change from transparent to colored states at the flick of a switch. Such devices can help to prevent heat loss and maximize the amount of natural light passing through windows. Sing Yang Chiam from the A*STAR Institute of Materials Research and Engineering in Singapore and co-workers have discovered how to improve the manufacturing and performance of smart windows by elucidating the critical roles that water molecules play during coloration.

Nickel oxide (NiO) is a low-cost, inorganic compound widely used as an anode material inside smart windows because it is a reversible color-changer. Unlike other electrochromic substances, however, researchers have struggled to comprehend how coloration occurs in NiO in the presence of common aqueous electrolytes. Part of the problem is that NiO can form different crystal structures in its bleached and colored states, depending on how much water becomes incorporated into the material.

Chiam and his team set out to unravel this puzzle with a 'chemical bath deposition' technique that allowed rapid fabrication of NiO thin films simply by dipping a conductive glass slide into a nickel precursor solution (see image). The researchers annealed the films at increasingly elevated temperatures to gradually drive water out of NiO, checking its structure with X-ray diffraction and infrared spectroscopy along the way. They also investigated how these structures had changed after multiple electrochromic color-change cycles.

The team's experiments revealed a complex coloration mechanism involving water and NiO particles. Initially, two intertwined reactions hydrated the thin film by turning NiO into nickel hydroxide. This process enhanced the material's optical response to electrical signals by allowing more of the thin film to contribute to coloration reactions. However, repeated cycling caused 'over-hydration' that trapped water molecules inside the thin film structure -- a development that degrades electrochromic activity by generating irreversibly colored nickel oxide hydroxide grains.

The researchers found that a simple high-temperature annealing process could mitigate the effects of over-hydration in the NiO thin film. This improved mechanistic knowledge -- in combination with their simple and scalable chemical dip coating technique -- helped them to achieve one of the best optical modulations reported for NiO films.

Currently, the team is investigating how to extend their work to flexible substrates. "Fabricating electrochromic thin films on rolls of plastic could make retrofitting onto existing windows affordable and easy," explains Chiam.

The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and Engineering


Story Source:

The above story is based on materials provided by The Agency for Science, Technology and Research (A*STAR). Note: Materials may be edited for content and length.


Journal Reference:

  1. Yi Ren, Wai Kin Chim, Li Guo, Hendrix Tanoto, Jisheng Pan, Sing Yang Chiam. The coloration and degradation mechanisms of electrochromic nickel oxide. Solar Energy Materials and Solar Cells, 2013; 116: 83 DOI: 10.1016/j.solmat.2013.03.042

Cite This Page:

The Agency for Science, Technology and Research (A*STAR). "Smart windows: Understanding how hydration affects color-changing windows can boost efficiency." ScienceDaily. ScienceDaily, 20 November 2013. <www.sciencedaily.com/releases/2013/11/131120103446.htm>.
The Agency for Science, Technology and Research (A*STAR). (2013, November 20). Smart windows: Understanding how hydration affects color-changing windows can boost efficiency. ScienceDaily. Retrieved October 21, 2014 from www.sciencedaily.com/releases/2013/11/131120103446.htm
The Agency for Science, Technology and Research (A*STAR). "Smart windows: Understanding how hydration affects color-changing windows can boost efficiency." ScienceDaily. www.sciencedaily.com/releases/2013/11/131120103446.htm (accessed October 21, 2014).

Share This



More Matter & Energy News

Tuesday, October 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Gulfstream G500, G600 Unveiling

Gulfstream G500, G600 Unveiling

Flying (Oct. 20, 2014) Watch Gulfstream's public launch of the G500 and G600 at their headquarters in Savannah, Ga., along with a surprise unveiling of the G500, which taxied up under its own power. Video provided by Flying
Powered by NewsLook.com
Japanese Scientists Unveil Floating 3D Projection

Japanese Scientists Unveil Floating 3D Projection

Reuters - Innovations Video Online (Oct. 20, 2014) Scientists in Tokyo have demonstrated what they say is the world's first 3D projection that floats in mid air. A laser that fires a pulse up to a thousand times a second superheats molecules in the air, creating a spark which can be guided to certain points in the air to shape what the human eye perceives as an image. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com
Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

3BL Media (Oct. 20, 2014) Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-fuel Impala Video provided by 3BL
Powered by NewsLook.com
What We Know About Microsoft's Rumored Smartwatch

What We Know About Microsoft's Rumored Smartwatch

Newsy (Oct. 20, 2014) Microsoft will reportedly release a smartwatch that works across different mobile platforms, has a two-day battery life and tracks heart rate. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins