Electrochromic response time

Electrochromic response time is the time the polymer takes in response to the potential pulse to go from fully coloured state 1 to fully coloured state 2. As conducting polymers are ion-insertion electrochromic materials, very fast electrochromic response times cannot be expected when polymer films are made thick enough to achieve sufficiently high differences in optical density between doped and undoped forms. 

The electrochromic performance of conducting polymers has been investigated since 1983 [7, 11-23], most of the studies having been carried out in liquid electrolyte. However, the data reported in the early papers are not exhaustive enough to evaluate the parameters necessary for the use of the electrochromic material in device technology. These data are generally of electrical response time only (i.e. the time the polymer takes to store charge) and may not be representative of electrochromic response time. 

The best performing is pMeT. Switching it between 2.5 and 4 V vs Li shows an electrochromic efficiency at 530 nm of 240mC cm, a very high value. Its electrochromic response time is also satisfactory, the transmittance... 

On the other hand, oxyalkyl-substituted polymers are also potentially attractive for the known cation coordinating properties of their ether groups, which are expected to improve ionic transport in the polymers and, hence, to give faster electrochromic response time. The ether-group compatibility of these polymers with polyethylenoxide-based polymer electrolytes is also expected to improve the electrode-electrolyte contact in solid-state electrochromic devices. 

Electrochromic iridium oxide films can be obtained by anodic growth or by sputtering, again on an ITO-coated glass support. It has been established [18] that properly deposited iridium oxide films can provide electrochromic response times of the order of 200 ms. Such a fast response, however, is in part counterbalanced by the high cost of the material. 

The electrochromic response times in organic acids are much less (50 ms for anodic, 40 ms for cathodic) as compared to H2SO4 [46,47]. 

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