Mechanical and microstructural properties of broadband anti-reflective TiO2/SiO2 coatings for photovoltaic applications fabricated by magnetron sputtering

• Published in: Solar energy materials and solar cells Vol. 220; p. 110841
• Main Authors: Zambrano, D.F., Villarroel, R., Espinoza-González, R., Carvajal, N., Rosenkranz, A., Montaño-Figueroa, A.G., Arellano-Jiménez, M.J., Quevedo-Lopez, M., Valenzuela, P., Gacitúa, W.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-01-2021; Elsevier BV
• Subjects: Anatase; Annealing; Anti-reflective coatings; Antireflection coatings; Broadband; Coatings; Durability; Environmental conditions; Glass substrates; Heat resistance; High temperature; Magnetron sputtering; Mechanical properties; Microstructure; Multilayers; Nanoindentation; Optical properties; Phase transitions; Photovoltaic cells; Photovoltaic solar panels; Photovoltaics; Plastic deformation; Reflectance; Resistance against plastic deformation; Room temperature; Silicon dioxide; Silicon substrates; Substrates; TiO2/SiO2; Titanium dioxide; Anti-reflective coatings; Photovoltaic solar panels; Magnetron sputtering; TiO2/SiO2; Resistance against plastic deformation
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2020.110841

Anti-reflective coatings are used in photovoltaic systems to minimize reflectance thus optimizing efficiency. Besides excellent optical properties, these coatings need to provide good mechanical properties due to hostile environmental conditions. Therefore, this study aims at designing anti-reflective coatings based upon multi-layers of TiO2 and SiO2 by magnetron sputtering on glass and silicon substrates at room temperature. Afterwards, these coatings were thermally annealed at 400, 500 and 600 °C to study the influence of such treatment on their optical and mechanical properties. Samples prepared at room temperature and annealed at 400 °C showed an optimized reflectance of about 2%. Advanced materials characterization techniques were used to elucidate the microstructural evolution of the multi-layers. The multi-layers annealed at 400 °C demonstrated a dense and smoothly packed microstructure with homogenous grains (50 nm in size), with a phase transformation from amorphous to anatase. In addition, exposure and damage of the glass substrate were detected for elevated temperatures (500 and 600 °C), thus increasing the reflectance. Nanoindentation revealed an improved hardness, elasticity, and resistance against plastic deformation for the sample annealed at 400 °C. Consequently, anti-reflective coatings with post-annealing treatment at 400 °C, unify two complementary aspects such as improved mechanical properties (extended durability) and enhanced collection abilities over a broader wavelength range (increased efficiency).
•Design of anti-reflective coatings (ARC) using TiO2/SiO2 multi-layers by DC/RF magnetron sputtering for photovoltaics.•In-situ optical emission spectroscopy verified reproducible process conditions.•Novel methodology to measure mechanical properties of thin films using XPM ultra-fast mode nanoindentation.•ARC with post-annealing improved mechanical properties and enhanced collection abilities.