Electrochromic devices (EC) consist of carriers, 1st conductive layer (typically transparent), ion storage layer, electrolyte layer, 2nd conductive layer, and encapsulation, as shown in the following picture.
Device structure
- Carrier: polymers, e.g. PET, PC; or glass
- Transparent conductor: typically ITO(1, 2), FTO
- Ion storage layer: NiO. Intrinsic NiO is transparent with brownish tint; with Li penetration, it becomes transparent.
- Electrolyte: Poylmers, liquid, or solids (LiAlF4, Ta2O5, Nb2O5, LiPON, et. al.)
- EC layer: WO3 is a good example; it is intrinsically transparent almost colorless; with Li penetration, it turns to be blue; less transparent with increasing Li intercalation(3).
- Encapsulation: inorganic barrier, e.g. SiO2, SiNx; or organic, e.g. epoxy.
Replacing glass carrier with plastic carrier, flexible EC devices can be made as an example in following
Key to make good EC devices
- Interface engineering among multilayers
- electrolyte materials and processing
- Morphology of EC layer
- Stoichiometry of ITO, WO3, and NiO; critical to achieve desired performances
- Coating process of each layer, particularly EC layer by sputtering
- Encapsultion
- Formation and electrical tests
- Others
Different EC technologies
- SPDs: Link