I've read a lot about electrochromism. This article on electrochromic materials has also been additionally helpful.
I was wondering, for these electrochromic materials, can you simply attach a small electrode to either side of the film like in setup 2, then apply a small voltage? Will the electrochromism only occur at the edges in this case?
Does anyone know how material dependent this effect is? I was hoping to use a polymer film in particular. enter image description here

  • $\begingroup$ Trivia: a slice of potato with some sodium or potassium iodide solution sprinkled on it makes a primitive electrochromic "display". Apply a few volts to wires immersed in the electrolyte; iodine released at the positive electrode turns the potato purple or black. If the reacti0n hasn't gone to far, it's reversible by changing polarity. [Sorry, it's not really an answer to your question, but perhaps someone will make a starch display.] $\endgroup$ – DrMoishe Pippik Jun 21 '15 at 4:46

I will answer your last question first, this is very material dependent. Not all materials will be electrochromic. It is a very specific effect where the material has different oxidation states that have different absorbance profiles(colors if you will). The most common ones are conducting polymers (https://en.wikipedia.org/wiki/Conductive_polymer) since these materials have different oxidation states that have vastly different electronic structure.

Two electrode electrochemistry can get pretty hard to understand. Two compare your setups 1 and 2, the main differences are the electrode area and the electrode distance. Other than that, the two are the same. So, yes, electrochromism will happen in setup2 as well. However, it is hard to predict exactly where it will happen and to what extent. It all depends on the material you select, it's resistance and doping characteristics. In either setup, it will start at the electrode and work it's way inward, obviously, setup 1 is more advantageous with the larger electrode area and shorter inter-electrode distance.


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