Multifunctional Antireflection Coatings Based on Novel Hollow Silica–Silica Nanocomposites

Abstract

Antireflection (AR) coatings that exhibit multifunctional characteristics, including high transparency, robust resistance to moisture, high hardness, and antifogging properties, were developed based on hollow silica-silica nanocomposites. These novel nanocomposite coatings with a closed-pore structure, consisting of hollow silica nanospheres (HSNs) infiltrated with an acid-catalyzed silica sol (ACSS), were fabricated using a low-cost sol-gel dip-coating method. The refractive index of the nanocomposite coatings was tailored by controlling the amount of ACSS infiltrated into the HSNs during synthesis. Photovoltaic transmittance (TPV) values of 96.86-97.34% were obtained over a broad range of wavelengths, from 300 to 1200 nm; these values were close to the theoretical limit for a lossy single-layered AR coating (97.72%). The nanocomposite coatings displayed a stable TPV, with degradation values of less than 4% and 0.1% after highly accelerated temperature and humidity stress tests, and abrasion tests, respectively. In addition, the nanocomposite coatings had a hardness of approximately 1.6 GPa, while the porous silica coatings with an open-pore structure showed more severe degradation and had a lower hardness. The void fraction and surface roughness of the nanocomposite coatings could be controlled, which gave rise to near-superhydrophilic and antifogging characteristics. The promising results obtained in this study suggest that the nanocomposite coatings have the potential to be of benefit for the design, fabrication, and development of multifunctional AR coatings with both omnidirectional broadband transmission and long-term durability that are required for demanding outdoor applications in energy harvesting and optical instrumentation in extreme climates or humid conditions.

In situ formation of artificial moth-eye structure by spontaneous nano-phase separation

“…Honestly, the low transmittance and high reflectance of the thin film in 400~600 nm are the disadvantages for the practical application in solar cells, which may due to the light scattering by the nipples and the large thickness of the thin film 26,27 . Furthermore, the refractive index of the moth-eye thin film was estimated by Equation 1 18 , and it is 1.319, which is a little higher than the refractive index (1.22) of optimal single-layer antireflective thin films on commercial glass 18,28 .Where, r is the reflectance of one side of thin film, n s , n air and n are the refractive index of the substrate, air and film, respectively. In fact, the moth-eye thin film has a gradient refractive index, which endows the coated glass with a low reflection (2.8%).…”

Fabrication of mechanically robust, self-cleaning and optically high-performance hybrid thin films by SiO2&TiO2double-shelled hollow nanospheres

“…10 Therefore, the AR thin films on solar glass must be able to resist external weathering, including moisture, rain and high temperatures. Typically, the solar glass used in PV modules usually encounters constant temperature between 21°C and 53°C during operation.…”

“…10,48 Mechanical properties of SiO 2 &TiO 2 DSHN thin films The corrosion takes place in two steps: (1) H + of water in the form of H 3 O + first diffuses into the glass and exchanges with cations, leading to a hydrated layer; (2) Si-O-Si bridging bonds are subsequently hydrated, breaking up the network and forming a gel, which leads to network dissolution.…”

“…[1][2][3][4][5][6] There would be no reflection if there is a destructive interference between the light reflected from the film-substrate and the air-film interfaces. [7][8][9][10][11] Among them hollow SiO 2 nanoparticles have been proved to be good building blocks for AR thin films because the inner cavity of the SiO 2 nanoparticles offers a large volume for tuning the RI of the AR thin films. 22.…”

Reduction of microbial biofilm formation using hydrophobic nano-silica coating on cooling tower fill material

“…The surface properties of the materials can be changed by coating application or surface modification, to create the desired anti-adhesion characteristics without altering the bulk properties of materials. Various coatings have been developed in order to achieve a variety of functional characteristics, including anti-scratch, anti-reflective, anti-fogging, anti-microbial or self-cleaning properties (Türetgen et al, 2012;Ovissipour et al, 2014;Zhang et al, 2014). Attempts have been made to reduce biofilm formation by coating surfaces with antimicrobials, by the incorporation of antimicrobial products into surface materials or by modifying the surface's physicochemical properties (Hetrick et al, 2009;Bruellhoff et al, 2010;Simoes et al, 2010.…”