VO2-Based Thermochromic Films Modified by Transparent Matter-Repellent Surfaces with Superior Self-Cleaning Ability and Mechanical Robustness.

Vanadium dioxide (VO2)-based thermochromic films are highly attractive for smart window applications due to their ability to dynamically modulate solar radiation in response to ambient temperature. However, their practical deployment is significantly hindered by poor long-term stability in outdoor environments, vulnerability to surface contamination, and insufficient mechanical durability. Herein, we propose a novel strategy to obtain self-cleaning and durable VO2 composite films, consisting of a VO2 thermochromic layer covered by either a SiO2 or TiO2 overcoat and further modified by a transparent and matter-repellent surface. Multifunctional VO2 composite films are rationally designed to exhibit superior repellence towards various liquids, thereby imparting excellent anti-fouling property. Crucially, the VO2 composite film is engineered for high optical transparency to ensure it does not compromise the solar modulation ability of the underlying VO2 layer. Furthermore, the robust mechanical properties of the SiO2 or TiO2 overcoat with matter-repellent modification provide effective protection against abrasion and scratch damages. The resulting VO2-based composite films demonstrate significantly enhanced environmental stability and operational reliability while maintaining desirable thermochromic performance. This work presents a promising strategy to overcome the stability and durability challenges facing VO2 smart windows, paving the way for their real-world application in energy-efficient buildings.