Artificial linear brush abrasion of coatings for photovoltaic module first-surfaces

• Published in: Solar energy materials and solar cells Vol. 219; p. 110757
• Main Authors: Newkirk, Jimmy M., Nayshevsky, Illya, Sinha, Archana, Law, Adam M., Xu, QianFeng, To, Bobby, Ndione, Paul F., Schelhas, Laura T., Walls, John M., Lyons, Alan M., Miller, David C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.01.2021; Elsevier BV
• Subjects: Abrasion; Anti-reflective coating; Anti-soiling coating; Atomic force microscopy; Bristles; Ceramic coatings; Chemical composition; Cleaning; Coatings; Contact angle; Damage detection; Depth profiling; Durability; Erosion; Failure modes; Fluoropolymers; Interferometry; Light microscopy; Microscopy; Modules; Morphology; Near infrared radiation; Nylon 612; Operations maintenance; Optical microscopy; Photoelectron spectroscopy; Photoelectrons; Photovoltaic cells; Photovoltaics; PMMA; Polymethyl methacrylate; Protective coatings; Silica; Silicon dioxide; Slurries; Solar radiation; Spectroscopy; Spectrum analysis; Surface energy; Surface properties; Surface roughness; Titanium dioxide; Water depth; Abrasion; Anti-reflective coating; Operations maintenance; PMMA; Anti-soiling coating; Erosion
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2020.110757

Natural soiling and the subsequent requisite cleaning of photovoltaic (PV) modules result in abrasion damage to the cover glass. The durability of the front glass has important economic consequences, including determining the use of anti-reflective and/or anti-soiling coatings as well as the method and frequency of operational maintenance (cleaning). Artificial linear brush abrasion using Nylon 6/12 bristles was therefore examined to explore the durability of representative PV first-surfaces, i.e., the surface of a module incident to direct solar radiation. Specimens examined include silane surface functionalized-, roughened (etched)-, porous silica-coated-, fluoropolymer-coated-, and ceramic (TiO2 or ZrO2/SiO2/ZrO2/SiO2)-coated-glass, which are compared to monolithic-poly(methyl methacrylate) and -glass coupons. Characterization methods used in this study include: optical microscopy, ultraviolet–visible–near-infrared (UV-VIS-NIR) spectroscopy, sessile drop goniometry, white-light interferometry, atomic force microscopy (AFM), and depth-profiling X-ray photoelectron spectroscopy (XPS). The corresponding characteristics examined include: surface morphology, transmittance (i.e., optical performance), surface energy (water contact angle), surface roughness, scratch width and depth, and chemical composition, respectively. The study here was performed to determine coating failure modes; identify characterization methods that can detect nascent failures; compare the durability of popular contemporary coating materials; identify their corresponding damage characteristics; and compare slurry and dry-dust abrasion. This study will also aid in developing an abrasion standard for the PV industry. Figure A: Representative images of the experimental configurations for the linear brush abrasion tester, including: (a) isometric view of the slurry tester, (b) isometric view of the dry-dust tester.Artificial linear brush abrasion was examined to explore the durability of representative PV first-surfaces. Specimens examined include silane surface functionalized-, roughened (etched)-, porous silica coated-, fluoropolymer coated-, and ceramic (TiO2 or ZrO2/SiO2/ZrO2/SiO2) coated-glass, which are compared to monolithic-poly(methyl methacrylate) and -glass coupons. Characterization methods included: optical microscopy, UV-VIS-NIR spectroscopy, sessile drop goniometry, white light interferometry, atomic force microscopy (AFM), and depth profiling X-ray photoelectron spectroscopy (XPS). The corresponding characteristics examined include: surface morphology, transmittance (i.e., optical performance), surface energy (water contact angle), surface roughness, scratch-width and -depth, and chemical composition, respectively. The study here was performed to determine coating failure modes; identify characterization methods that can detect nascent failures; compare the durability of popular contemporary coating materials; and identify their corresponding damage characteristics; and compare between slurry and dry dust abrasion. [Display omitted] •Correlation between transmittance, yellowness, surface energy, and roughness consistent with history of film degradation.•Damage primarily results from the facets and edges of dust particles and/or brush bristles, i.e., localized abrasion sources.•A variety of longevities from 100 cycles to 1000 cycles to 10000 cycles was observed for the representative specimens here.•Test parameter details as well as post examination suggest improvement of the linear artificial brush abrasion method.