Does anyone know exactly how Photochromic and electrochromic glass works, ive been doing some research and could not find an explicit explanation. Any help would be greatly appreciated.

While the glass is still molten, Silver-Chloride and Copper(I)-Chloride are added. The glass crystalizes and the addatives are evenly distributed throughout the glass.

Light catalyzes a reversible reaction.

The silver is reduced and the chloride is oxidized, resulting in silver and chlorine (as a gas, trapped within the glass). The silver darkens the lens.

When light is removed, chlorine oxidizes the Cu(I) to Cu(II), the Cu(II) oxidizes the silver, and you are left with what you started with.

The basic idea of electrochromic is a small voltage is placed across a very thin layers and this changes the charge on an electrochromic layer. Electrochromic means the colour changes when a voltage is applied. So changing the charge of the electrochromic layer will change it's colour.

 

All I know about photochromic is that it gets darker when exposed to light (like in some sunglasses).

 

See here:

http://electronics.howstuffworks.com/smart-window.htm

 

Question on photochromic sunglasses:

http://science.howstuffworks.com/question412.htm

IIRC, it`s something to do with Copper and Silver Chloride molecules mixed in with the glass.

silver chloride when exposed to UV turns into silver metal with a brown(ish) appearance when very fine, the chloride ion then reacts with the copper making copper chloride.

after the UV is taken away the whole thing reverses again, and you get copper ions and silver chloride molecules again due to a displacement reaction, leaving both ions and molecules back in their original near transparent state.

bjmyanks, don't double post, can I suggest a mod moves MattC's post into the clone-thread found here:

http://www.scienceforums.net/forums/showthread.php?t=17755

(suggested it that way around as there is only 1 post in here, whereas there is 2 in the other)

DAMN! I merged the wrong direction!

 

Grrr... forget it for now, I`ll sort it later