Surface Treatments for Electrochromic Glazing: Toward Reduced Costs and Optimal Performances through Ultrasonic Spray Pyrolysis

Research and industrial interests for electrochromic “smart” windows have considerably grown those recent years due to their potential use as an energy-saving material for buildings. Their CO₂ emission can be significantly reduced by decreasing their energy consumption up to 30%.

The crucial issues of such devices are the coloration efficiency as well as the reversibility upon coloration and bleaching of the electrochromic layers. The combination of WO₃ and Li-doped NiO surface films (separately as working and counter electrodes) affords a good coloration contrast between colored and bleached states of the device, since tungsten oxide colors upon electrons and ions insertion while nickel oxide gets colored after their extraction.

In order to improve the performances of those electrochromic films, we have studied the effects of a surfactant-assisted deposition process of both individual layers through Ultrasonic Spray Pyrolysis (USP). This technique indeed constitutes a low-cost alternative to industrial vacuum processes for manufacturing high quality thin films.

The crystallization and morphology of those films, as well as their optical, electrochromic and electrochemical properties have been investigated. The presence of surfactant in the precursor solution has led to improved wetting of liquid droplets sprayed on the heated FTO/glass substrate. The resulting films testify for a better homogeneity and a higher active surface, which also allows for enhanced reversibility and coloration contrast.