Sponsored Student: Enhancing the chemical durability of electrochromic materials for energy saving and security applications

Smart windows based on electrochromic materials have yet to properly breach the market. This is mainly due to two issues: 1) the fabrication costs are still quite high, and 2) the durability of the system as a whole still requires improvements. Our latest research addresses both of these issues.

Traditional WO₃ films, the main constituent of electrochromic windows, are deposited at higher pressures (20-30 mTorr) to generate sufficient porosity and ensure high ionic mobility. In the present work we explore different approaches to control the porosity, diffusion coefficient, coloration efficiency as well as implementation of WO₃ in more complex multilayer structures. The resulting film performance is tested using cyclic voltammetry in a 0.1 M H₂SO₄ electrolyte and other complementary methods. We systematically categorize the coating properties based on the coloration efficiency, dynamic behavior and the chemical durability. For certain approaches we found that the deposition rate is five times higher compared to the standard fabrication methods, while the long term stability is significantly enhanced. The film performance is explained in terms of a microstructural model based on the compositional and microstructural characteristics.