A few blogposts ago I wrote about our new synthesis method of making transparent yttrium hydride films. Yttrium and yttrium hydride films have earlier been used to make smart windows taking advantage of the hydrogen absorbtion in yttrium. It's a facinating reaction that was studied for many years, but due to a few drawbacks of this technology, it calmed off and never reached the market.
Now, just recently we made a discovery that might draw the attention to yttrium hydride based smart windows again. We found out that the transparent yttrium hydride films we had made had a very interesting reaction to light; they turned dark when they were illuminated! Under direct sunlight they gradually change colour, and the transparency is reduced by up to 50%. After the light exposure the material gradually turns back to its inital transparent state. This reaction is called photochromism, a very rare reaction which is observed very few existing materials.
The photochromic reaction in films of transparent yttrium hydride.
The reaction to light is indeed very fascinating. The video below gives an impression on how it works on a small sample deposited on glass, exposed to sunlight in our laboratory:
Imagine if a building in a hot and sunny area could reduce the energy consumption for cooling by up to 50% just by changing the windows! There are even more possible applications for this type of material, as sunglasses, displays, data storage etc. At the current stage we are working more on understanding what is really happening in this material and how to control the photochromic reaction.
Paper: "A new thin film photochromic material: Oxygen-containing yttrium hydride".
Published in: Solar energy materials and solar cells
DOI: 10.1016/j.solmat.2011.08.018
