Electrochromic Materials Switching Time

So I've been curious about electrochromic materials lately. In particular, the amount of time it takes for it to switch from transparent to translucent and back. Is the switching time a function of how much material you are applying the voltage across or something? Also, is there any specific electrochromic material that switches faster than others?

I've seen different videos of it, and for the most part, it seems that they switch to transparent faster than they switch to translucent, like in this video:
http://www.youtube.com/watch?v=6qUc-x_DrHU

Any input anybody can give me would be appreciated!