Increasing performance of electrochromic devices by modifying surface and charge ratio between electrodes

Surface and charge ratios between the two electrodes of an electrochromic cell have been shown to be variables that affect their optical and electrochemical performance. By changing the charge ratio, at fixed applied potentials, one of the electrodes decreases its oxidation state variation, therefore lowering its electrochromic response. If the ratio is increased to high enough values the electrode will act as an ion storage layer. Surface ratio also varies the charge ratio, but offers the possibility to use increasingly transparent ion storage layers, which in turn translate into better contrast of the corresponding device.The results obtained suggest a new configuration for electrochromic devices, in which optoelectrochemical performance can be optimized without the use of complementary materials.

Graphical abstractPhotopic contrast of an electrochromic cell as a function of charge and surface ratio of their electrodes. Straight line indicates the contrast for the working electrode alone, which constitutes the limiting contrast of the cell.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Proof of concept for a new design of electrochromic devices. ► Optical limitations of dual electrochromic devices overcame. ► Electrodes surface and charge ratio influence optoelectrochemical performance.