Microstructural analysis of selective C/Al2O3/Al solar absorber surfaces

• Published in: Thin solid films Vol. 425; no. 1-2; pp. 24 - 30
• Main Authors: KONTTINEN, P, KILPI, R, LUND, P. D
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier Science 03.02.2003
• Subjects: Applied sciences; Composition; defects and impurities; Condensed matter: structure, mechanical and thermal properties; Energy; Exact sciences and technology; Natural energy; Photovoltaic conversion; Physics; Solar cells. Photoelectrochemical cells; Solar energy; Solid surfaces and solid-solid interfaces; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Aluminium oxide; Scanning electron microscopy; Property composition relationship; Duralumin; Atomic cluster; Aluminium; Solar absorbers; Experimental study; Grinding; Inorganic compound; Surface; Thermal properties; Solar cell; Optical properties; Thermal emissivity; Graphite; Optical coating; Chemical composition; Manufacturing; Microstructure; Optical coatings; Optical absorption
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/S0040-6090(02)01141-0

The elemental composition and geometrical structure of mechanically manufactured spectrally selective C/Al2O3/Al solar absorber surfaces were characterized by XPS, scanning electron microscopy, energy dispersive X-ray spectroscopy and optical microscopy. The XPS analysis revealed that the surface contains Al2O3 and C in graphite form. Optical microscopy confirmed that graphite forms inhomogeneous agglomerated clusters on the surface. The thickness of the clusters varies, the maximum measured thickness being in the range of 300 nm. A solar absorptance of 0.90 and a thermal emittance of 0.22 have been achieved so far. Increasing the graphite coverage and decreasing the graphite cluster thickness could increase the absorptance to greater than or equal to 0.94 and lower the emittance. This could be achieved by altering the composition and the structure of the grinding pad used and by finding the suitable manufacturing parameters for the advanced pad. 18 refs.