Combining energy efficiency with self-cleaning properties in smart glass functionalized with multilayered semiconductors

We propose here a new approach based on a combined study of the self-cleaning and energy-efficiency properties of stratified WO₃/Cu–TiO₂ coatings for glazing applications. The multifunctional performance was investigated by varying the number of layers deposited on the glass substrate (i.e., 1, 2, 4 layers), while energy efficiency was assessed using building energy modeling. Results indicate that the self-cleaning ability can be boosted by a multilayer configuration due to the inhibited charge recombination and to a gradual rise in surface roughness and porosity with the increasing number of layers. In particular, the highest wettability and degradation of toluene under simulated solar light were achieved over the coating consisting of Cu-doped TiO₂ stacked with WO₃ in a 4-layer configuration. On the other hand, the analogous sample, but in the 2-layer configuration, was the most active sample in the oxidation of carbon monoxide. In terms of energy efficiency, the applied coatings led to important energy savings, exceeding 8% in total energy consumption and 18% in cooling loads. The best energy efficiency levels in the tested glazing configurations were achieved with single-layer WO₃. However, its low visible transmittance reduced the amount of natural daylight entering the studied buildings, unintentionally increasing the electric lighting loads. The results highlight the importance of alternative configurations, such as Cu-doped TiO₂ in a dual-layer arrangement with WO₃, which provide a better balance between energy efficiency and access to daylight, an important driver of occupant comfort and wellbeing.