Mirage detection is an interesting technique used to monitor the flux of counter-ion between an electrochromic film and a liquid electrolyte during voltammetric experiments. The mirage effect occurs when a light probe, such as a laser beam, passing through a layer of variable refractive index is deflected. It was first discovered as the result of a temperature gradient, and called `photothermal mirage effect.' It can also result from a concentration gradient due to a flux of electroactive species or counter-ions. This later case allows investigation directly in the direction of counter-ion flux between an electrolyte solution and a thin film of a material, i.e., to know whether the counter-ion exits or enters the film. The mechanism of transfer between the electrode and the solution can then be directly evidenced. This paper presents three examples of experiments, issued from the laboratory, illustrating the possibilities of the technique for studying electrochromic materials.
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