Thermally evaporated Cu–Al thin film coated flexible glass mirror for concentrated solar power applications

This paper reports the development of mechanically flexible reflective coatings of Cu–Al intermetallic alloy on flexible glass (FG) substrates for possible concentrated solar power application. Thin films of Cu–Al intermetallic alloys were deposited on 100 μm thick FG substrates using resistive thermal evaporation of arc melted Cu–Al bulk alloy. At the optimized evaporation conditions, smooth intermetallic alloy thin films with homogeneous composition (Cu0.78Al0.22) were obtained. At a coating thickness of 160 nm, average specular and total reflectance of ∼84% and ∼92% respectively, were achieved. The films exhibited hydrophobic nature with a contact angle of 102°, implying the possibility of developing a self-cleaning ability. The analytical calculation involving alloy compositional dependence of plasma frequency reveals the prospect of further modulating the reflectance property by carefully tailoring thin film composition. Additionally, hard intermetallic thin film provides the opportunity of developing mirrors that may not require top protective coatings