Temperature dependence of electrochromic processes in iridium oxide displays

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Abstract
We report measurements of the temperature dependence of coloration and bleaching times of electrochromic iridium oxide films in the range +20 to −43 °C. The intrinsic response times increase gradually with decreasing temperature according to an activation energy of ∼0.25 eV. For a contrast ratio of ∼4:1, suitable for a practical device, we find that the response times remain below ∼0.25 sec for T⩾−10 °C and below 1 sec for T⩾−25 °C. We have also found that the temperature variation of the response times is independent of pH, so that an optimized electrolyte can be chosen for a practical device. Moreover, its independence of pH suggests that the electrochromism of iridium oxide is due to insertion and fast‐ion diffusion of the same ion species in either basic or acidic aqueous electrolytes.