Fig. 1. Schematic diagram of the solar selective absorption film with a typical four-layer film structure

Fig. 2. The refractive index n and extinction coefficient k spectra of the simulated material X as the absorption layer

Fig. 3. Maxwell-Garnett's diffuse microstructures（a） real microstructure，（b） ideal situation

Fig. 4. Bruggeman's aggregate microstructures（a） real microstructure，（b） ideal situation

Fig. 5. Absorption spectra of the four-layer structure with the absorption layer consisting of metal-metal alloy and metal-dielectric cermet， respectively

Fig. 6. Measured（symbol） and fitted（line） ellipsometric parameter Ψ and Δ，（a） and（b）， of the composite films at the incident angle of 65°

Fig. 7. The refractive index n and extinction coefficient k，（a） and（b）， of the Ti-MgF₂ nanocomposite thin films at different concentrations of Ti

Fig. 8. Absorptance of new four-layer photon-to-heat conversion film compared to that of previous four-layer and six-layer film structures using Ti as the absorption layer

Fig. 9. Measured and simulated absorptance of the new four-layer film structure with high photon-to-heat conversion efficiency

Fig. 10. The SEM image of the new four-layer film structure