Thin films of some transition metal oxides, organic polymers and inorganic complex compounds change their absorption and reflection behavior for electromagnetic radiation (especially for visible light and heat in the near infrared spectral range) due to the reversible insertion/extraction of electrical charges.

Electrical and optical switching and storage behavior
of an electrochromic device controlled with rectangular voltage pulses.
(T = light transmittance, I = current density, U = voltage)

The energy necessary for the coloration of our electrochromic glazing is low (between 20 and 150 Ws/m²) with a change in light transmittance in the visible spectral range between 70 and 10%. The d.c. voltage for switching the electrochromic window is between 0.5 and 2.2 V.

Reversible time dependent changes in the transmission
spectrum of an electrochromic window. The structure of the device is shown
in the diagram (active area 100 cm², driving voltage 1.75 V)

The coloration and bleaching rate depends on the following parameters:

• coloration efficiency of the electrochromic materials
  
  
• size of the electrochromic element
  
  
• electronic conductivity of the transparent conducting oxide films
  
  
• ionic conductivity of the polymer electrolyte

Depending on the choice of these parameters full coloration or bleaching of the electrochromic glazings can be achieved in time ranges between 2-10 seconds and 5-10 minutes. A multitude of different colors (e.g. blue, green, red, brown, violet, grey) can be realised.