Electrochromic device based on nanocrystalline materials

Electrochromic devices (e.g., displays) comprising a first electrode, a second electrode, and an electrolyte sepg. the electrodes in which ≥1 one of the electrodes includes an elec. active structure which has an at least dual state visual appearance depending on the p.d. between the electrodes are described in which ≥1 of the electrodes is a nanostructured conducting or semiconducting film which does not have an redox active species added to the surface and the electrode(s) together with the electrolyte are arranged for supporting a capacitive charge compensation. Methods for change of state of an elec. active structure in an electrochromic device are also described in which a capacitive charge compensation between ions in the electrolyte and the electrodes occurs after applying a voltage between the first and second electrode so that the change of state of the elec. active structure occurs without transfer of charge between the electrolyte and the electrodes.