Optimization of AlxOy/Pt/AlxOy multilayer spectrally selective coatings for solar–thermal applications

Abstract Spectrally selective Al x O y /Pt/Al x O y multilayer absorber coatings were deposited onto corning 1737 glass, Si (111) and copper substrates using electron beam (e-beam) vacuum evaporator at room temperature. The employment of ellipsometric measurements and optical simulation was proposed as an effective method to optimize and deposit multilayer solar absorber coatings. The optical constants ( n and k ) measured using spectroscopic ellipsometry, showed that both Al x O y layers, which used in the coatings, were dielectric in nature and the Pt layer was semi-transparent. The optimized multilayer coatings exhibited high solar absorptance α  ∼ 0.94 ± 0.01 and low thermal emittance ɛ  ∼ 0.06 ± 0.01 at 82 °C. The Rutherford backscattering spectroscopy (RBS) data of Al x O y /Pt/Al x O y multilayer absorber indicated the Al x O y layers present in the coating were nearly stoichiometry. The scanning electron microscope analysis (SEM) result indicated that the average diameter and inter-particles distance of Pt grains were statistically about 146 ± 0.17 nm and 6–10 ± 0.2 nm respectively.

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