Engineering a structurally robust aluminum-based front surface solar reflector: High broad-band reflectance and corrosion resistance

Aluminum (Al)-based solar reflectors are promising candidates for next-generation concentrated solar power (CSP) technologies due to their mechanical robustness, low density and structural scalability. However, their long-term performance is limited by oxidation, corrosion, and surface instability, necessitating engineered surfaces that maintain high broadband reflectivity and resist environmental degradation under prolonged outdoor exposure. To address these challenges, we design and fabricate an Al 2 O 3 -Ag-SiO 2 multilayer on an Al substrate via magnetron sputtering, yielding a dense, crack-free surface morphology (roughness of 9.1 nm). The optimized (SiO 2 –250 W) multilayer films exhibited low angular sensitivity over the investigated 10–80° incidence range, achieving a solar-weighted reflectance ( SWR ) of 96.01% with a peak reflectance of 99.34% (300–2500 nm) and a high mid-infrared reflectance of 99% (2.5–15 µm), thereby minimizing thermal radiation losses. The multilayer exhibited excellent corrosion resistance under salt spray and the Kesternich test, with SWR losses of only 1.93% after 600 h and 2.21% in a SO 2 -rich environment, respectively. The multilayer showed superior environmental durability in an accelerated weathering test, with SWR loss of only 1.2% after 550 h, and exhibited hydrophobicity with a contact angle of 123.42°. Additionally, nanoscratch testing showed that, at a fixed SiO 2 deposition power of 100 W, incorporation of the Al 2 O 3 interlayer increased the load required for extensive coating removal from 31.9 to 49.0 mN. The optimized SiO 2 –250 W multilayer reached 52.6 mN, indicating improved resistance to scratch-induced damage. These results show that multilayer films can provide high-performance, durable Al-based front surface reflectors for CSP systems.