Researches aiming solar energy management have been widely developed in the last years. Ambient and economics interests lead several laboratories to try to find new solutions to these problems. Optical active materials with tuning transmittance or reflectance are studied due to its potential applications in saving energy devices. These materials, called chromogenic materials, are known for its ability to change the optical properties depending on the applied external perturbation.

Electrochromism is a phenomenon related to color change produced by the application of an external electric field. New electrochromic devices with the active material in the electrolyte were developed in the last years. They are based on the metal deposition/dissolution on a transparent substrate produced by the passage of current. The transmittance or reflectance change is related to the amnount of charge passed by the system. Three stages of the electrochromic system based in bismuth electrodeposition: transparent (no Bi depostition) – dark (Bi depostion) – transparent (Bi dissolution), are shown in the figure.