Browsing by Keyword "Silica"
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Item Antireflective mesoporous silica coatings by optimization of water content in acid-catalyzed sol-gel method for application in glass covers of concentrated photovoltaic modules(2019-01-15) Agustín-Sáenz, Cecilia; Machado, Maider; Tercjak, Agnieszka; Tecnalia Research & Innovation; VALORIZACIÓN DE RESIDUOSPorous silica layers with outstanding antireflective properties have been prepared by acid-catalyzed sol-gel process in presence of organic phases as structure directing agents (SDA) and excess water, with the aim of offering a cost-competitive, easy up-scaling and high efficiency process that contributes to reduce current levelized cost of energy (LCOE) of concentrating photovoltaics (CPV). The process has been optimized by controlling the water/alkoxide ratio, which is an important structure-regulating tool, having a strong influence in the structural properties of sol-gel synthesized materials. Hydrolysis of the inorganic precursor has been accomplished in high water/alkoxide conditions and in the presence of SDAs. Evaporation induced self-assembly (EISA) during coating deposition and the scanning of four types of SDAs have permitted to select the coating that fulfilled specific thickness and refractive index values with, in parallel, excellent results on sol stability. The final optimization has produced mesoporous coatings with ∼9 nm mean pore size, leading to an enhancement in transmittance up to 7.4% over bare glass in the 300–1500 nm wavelength range. The transmittance spectra have been used as inputs for the theoretical calculation of the short-circuit current density of a commercially available multijunction solar cell for CPV applications.Item Broadband antireflective coating stack based on mesoporous silica by acid-catalyzed sol-gel method for concentrated photovoltaic application(2018-11) Agustín-Sáenz, Cecilia; Sánchez-García, José Ángel; Machado, Maider; Brizuela, Marta; Zubillaga, Oihana; Tercjak, Agnieszka; Tecnalia Research & Innovation; VALORIZACIÓN DE RESIDUOS; INGENIERÍA DE SUPERFICIES; SISTEMAS FOTOVOLTAICOSSilica multi-layer stacks have been designed with the aim to provide broadband antireflective (AR) properties for glass components in concentrated photovoltaic (CPV) application. Silica porous coatings were grown by combining acid-catalyzed sol-gel route and evaporation induced self-assembly (EISA) method with four types of organic/inorganic systems. Sols were prepared using tetraethylorthosilicate (TEOS) as inorganic precursor assembled with two di-block copolymers, one tri-block copolymer and one cationic surfactant as organic templates. Optical properties were characterized by ellipsometry and spectrophotometry while the material structure was analyzed by environmental ellipsometric porosimetry (EEP) and atomic force microscopy (AFM). The concentration of inorganic and organic phases was optimized and a broadband AR bi-layer stack was obtained providing a 7.2% (under the reference AM1.5 solar spectral irradiance) increase in transmittance over bare glass in the wavelength range 300–2000 nm when coated on both sides.