Silica Antireflective Coatings Research Articles

Quasi-in-situ characterization and laser damage investigation of flaws in silica antireflection coatings

Quasi-in-situ characterization and laser damage investigation of flaws in silica antireflection coatings

Mussel-inspired antimicrobial and antireflective Ag-NPs/PDA/SiO2 coatings via interfacial functionalization

Utilizing surface chemical engineering to endow interfacial special functionalities is effective for fabricating antireflection coating with antibacterial activity. Herein, we present a mussel-inspired dopamine (DA) interfacial functionalization strategy to modify porous silica antireflection coatings, forming a sandwich composite structure composing an antireflective, intermediary, and antibacterial layer. The low refractive index antireflective coating formed by porous silica with developed pore structure greatly improves the light transmittance, and provides a trace of moisture and oxygen channels to facilitate the activation of Ag-NPs, significantly increases the antimicrobial efficiency of the coatings. PDA helps Ag-NPs to be uniformly dispersed and anchored on the surface of the silica, which significantly enhances the antibacterial performance and durability. In addition, the introduction of PDA reduces the surface roughness of the coating, thus reducing light scattering and attenuating the negative effect of Ag-NPs on light propagation. Under the optimal conditions, the antibacterial rate of GSPA-0.1–10 exceeds 99.9999 % (E. coli and S. aureus antimicrobial rate > 99.9999 % at 40 min and 3 h, respectively), and the light transmittance was maintained above 96 %. This work demonstrates a synergistic interaction between porous silica and PDA, which will provide a new approach for the functionalization of porous antireflective coatings.

Improvement of the environmental stability of sol-gel silica anti-reflection coatings

Improvement of the environmental stability of sol-gel silica anti-reflection coatings

UV resistance of sol-gel hydrophobic silica antireflective coatings

UV resistance of sol-gel hydrophobic silica antireflective coatings

Enhancing mechanical stability of sol-gel silica antireflection coatings via ammonia treatment at low temperature

Silica antireflection coatings from sol-gel processes are of great importance in optical areas because of their capability to reduce light reflection and hence to increase transmission. However, it retained a challenge to enhance the mechanical durability of the sol-gel antireflection coatings. One option is to introduce strong chemical bonding between neighboring silica nanoparticles in the coatings. Here, we demonstrate that ammonia treatment is an effective approach to enhance the mechanical durability of the silica antireflection coatings. The coatings after ammonia treatment exhibited excellent mechanical properties, with tensile hardness of 4.4 GPa, pencil hardness of 4H, and good abrasion resistance, which is noticeably better than the coatings without ammonia treatment. The ammonia treatment did not impair the optical property of the coatings. The coatings after ammonia treatment remained their good transmission, with peak transmittance as high as 99.8%. Mechanism analysis suggests that the enhancement of the mechanical durability is likely due to the condensation of silanol groups between the neighboring silica nanoparticles under ammonia catalysis. The ammonia treatment provides a promising alternative to current approaches for improving the mechanical durability of the sol-gel silica coatings.

Correction to Highly Stable and Efficient Mesoporous and Hollow Silica Antireflection Coatings for Perovskite Solar Cells

Correction to Highly Stable and Efficient Mesoporous and Hollow Silica Antireflection Coatings for Perovskite Solar Cells

Highly Stable and Efficient Mesoporous and Hollow Silica Antireflection Coatings for Perovskite Solar Cells

Fresnel reflection at the air–substrate interface of a solar cell inevitably occurs causing an important optical loss in photovoltaic conversion efficiency. Transparent materials with a low reflect...

Surface free energy and microstructure dependent environmental stability of sol–gel SiO2 antireflective coatings: Effect of combined vapor phase surface treatment

Environmental stability is of great interest for sol–gel porous antireflective (AR) coatings. In this work, sol–gel silica AR coatings with excellent environmental stability were prepared via ammonia vapor treatment (AVT) combined with organosilane (hexamethyldisilazane (HMDS) or hexadecyltrimethoxysilane (HTMS)) vapor treatment. The surface free energy (SFE) of the coatings treated with different approaches was estimated through Owens–Wendt method combined with Wenzel equation from the contact angles of water, glycerol and diiodomethane. Scanning electron microscope and Fourier transform infrared spectroscopy were employed to study the surface morphology and chemical composition of the silica coatings treated with different methods. The silica coatings treated by combined vapor phase method possess the SFE of 24.11 mJ·m−2 for N-HD-SiO2 and 34.18 mJ·m−2 for N-HT-SiO2. After being placed in a 90%RH humid environment for 2 months, the peak transmittance of BK7 glasses coated with N-HD-SiO2 and N-HT-SiO2 only decreases by 0.58% and 0.95%, respectively. Meanwhile, N-HD-SiO2 and N-HT-SiO2 coated BK7 glasses also show quite stable optical transmittance after exposure to a vacuum oil environment for 2 months. The mechanism of the combined vapor phase surface treatment is discussed based on the combination analysis of surface morphology, chemical composition and SFE of the coatings.

Design of four-layer tri-wavelength silica antireflective coatings with vector method containing absentee layer

Abstract A four-layer tri-wavelength silica antireflective (AR) coating with 100% transmittance simultaneously at 1064 nm, 532 nm and 355 nm was designed based on the vector method combined with absentee layer. The type of this AR coating is λ/2-λ/4-λ/2-λ/4 (λ0 = 532 nm): 1.0|L A1 H A2|1.46 with nL = 1.19, nA1 = 1.31, nH = 1.44 and nA2 = 1.33.

Durable silica antireflective coating prepared by combined treatment of ammonia and KH570 vapor

Sol–gel silica antireflective (AR) coatings possess a high specific surface area that is more susceptible to be contaminated by absorption of contaminants from the environment, which will increase the refractive index and reduce the transmittance. Ammonia and γ-methacryloxypropyltrimethoxysilane (KH570) vapor treatment was employed to passivate the silica AR coating, thereby enhancing the environmental stability. The properties of the coatings were characterized with Fourier transfer infrared absorption spectroscopy, scanning electron microscopy, atomic force microscopy, UV–Vis–NIR spectrometer, and contact angle measurement. The results showed that after the vapor treatment, the coatings became denser and the environmental stability was greatly improved. After being exposed to a humid environment (RH > 90%) and low-vacuum environment with intentionally induced organic contaminants for 60 days, the transmittance of the modified SiO2 coating decreased by only 0.08% and 0.2%, respectively. Meanwhile, the average transmittance decreased by only 0.02% after being rubbed for 1000 cycles, indicating that the co-treated coating also possessed a good abrasion resistance.

Process study about silica anti-reflection coatings prepared by sol–gel method for cadmium telluride solar cells

Silica (SiO2) thin films with different refractive indexes as the anti-reflection coating for cadmium telluride (CdTe) solar cells were prepared by sol–gel method in this paper. In order to obtain the preparation process of SiO2 films with suitable refractive index, the different hydrolysis processes relied on the acid-base environment as well as the ratio of reactants was studied, respectively. It mainly includes that (I) the gel growth model in hydrogen or hydroxide ion environment provided by hydrochloric and ammonia. (II) The ratio of solvent, precursor and catalyst under base catalysis. (III) The weight and amount of polyethylene glycol molecular which is an additive agent to increase the porosity of sol film under acid catalysis. Based on the results above, a monolayer SiO2 coating with optimized refractive index was applied onto the glass substrate of CdTe solar cell, and the quantum efficiency has been enhanced at the band of 400–800 nm. After that, multilayer SiO2 coatings with high–low refractive indexes were designed according to the Fresnel theory to achieve wider spectrum (390–870 nm) enhancement. The broadband anti-reflection coatings (BARCs) were deposited on CdTe solar cell. The results were not consistent with expectations, which required further study about process matching between BARCs and device manufacture.

Surface Modification of Sol-Gel Silica Antireflective Coatings by F-PMHS: A Simple Method for Improvement of Amphiphobicity

Sol-gel silica antireflective coatings (ARCs) with improved amphiphobicity were simply fabricated on BK7 glass substrates via fluorinated-poly(methylhydrogen)siloxane (F-PMHS) surface modification by the dip-coating method. The results of Fourier Transform Infrared (FTIR) and X-ray Photoelectron Spectroscopy (XPS) showed that F-PMHS were covalently bonded to the surface of ARCs. F-PMHS modification significantly improved hydrophobicity and oleophobicity of silica ARCs by increasing their water contact angles from 27° to 105° and oil contact angles from 17° to 45°. In addition to the improved amphiphobicity, the modified ARCs also possessed excellent transmittance. Most importantly, it was found that with increasing F-PMHS content the atom amounts and porous property of modified ARCs were almost unchanged. This result had been shown to be associated with the changes of optical property and amphiphobicity for silica ARCs, and the details were discussed.

Universal Low-Temperature Process for Preparation of Multifunctional High-Performance Antireflective Mesoporous Silica Coatings on Transparent Polymeric Substrates.

In this work, we developed a universal low-temperature process for the preparation of multifunctional and robust mesoporous silica antireflective coatings on transparent polymeric substrates. The mesoporous silica layer was formed after UV-O3 exposure and ammonia vapor treatment of dried poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (F127)-containing acidic silica gel. The optical and antiscrubbing properties of the mesoporous silica coating were comparable to those of the coating prepared at 250 °C. The highest optical transmittance reached 99.55%, and the transmittance loss was only 1.02% after 400 scrubbing cycles. The coating surface formed by the low-temperature process was hydrophilic, resulting in excellent antifogging properties. The low-temperature process was successfully applied on various transparent polymeric substrates including polyimide, polyethylene terephthalate, polyethylene naphthalate, and polycarbonate. The excellent optical and mechanical performances of the mesoporous silica antireflective coatings on transparent polymeric substrates allow a wide range of practical applications, especially in the field of flexible electronics.

Comparative study on cracking behavior of sol-gel silica antireflective coating for high-powered laser system

Abstract Potassium dihydrogen phosphate (KDP) crystal is a kind of very crucial nonlinear optics for high-powered laser equipment as frequency conversion (doubler, tripler or quadrupler) components. In this paper, investigation on cracking behavior of sol-gel silica antireflective (AR) coatings has been performed using KDP crystal as substrate. Cracking induced by heating or moisturizing post-treatment is respectively studied, in which distinct cracking behaviors have been observed. It has been interestingly found that either temperature or humidity saltation can result in coating crack generation, but the corresponding residual stress demonstrates in completely reverse ways, giving rise to distinctive crack morphology on both crack edge and bottom. The origination and the derivation of such stress manner have been stated based on the intrinsic porous structure of sol-gel silica coating, and the critical cracking condition has been suggested dependent on the relationship between the accumulated residual stress against elastic recovery capability of such coating.

A simple method to control the microstructure and properties of sol–gel silica antireflective coatings

To control the microstructure and properties of sol–gel silica antireflective (AR) coatings, a simple PMHS (poly(methylhydrogen)siloxane) surface modification method was applied and investigated.

Influence of TEOS concentration and Triton additive on the nanostructure silica sol-gel anti-reflective coatings

Nanostructured silica antireflective coatings were fabricated on glasses by sol-gel technique. Various silica sols [varying in composition: tetraethyl orthosilicate (TEOS) concentration and Triton additive] were synthesised by the acidic catalysed process and then subsequently coated on substrates. The coatings prepared in this work were characterised using UV-visible spectroscopy, Fourier-transformed infrared spectrophotometer and filed emission scanning electron microscopy. Results indicated that the dense silica films permit a considerable reduction of these light reflections compared with uncoated glasses in all the cases studied, but the degree of reduction is different depending on the composition of the precursor solution. It was found that the transmittance increased from 0.915 for the bare slide up to 0.96 for the best made sample corresponding to the Triton-doped silica. The addition of Triton x-100 to the silica sols improved the optical property of thin films due to existence of nanoporous in the coatings. The SiO2 concentration is an effective parameter to prepare the antireflective films. Decrease in SiO2 precursor cause to decrease in gelation time and, therefore; the suitable SiO2 particles and pores are well formed.

High-Quality Hollow Closed-Pore Silica Antireflection Coatings Based on Styrene-Acrylate Emulsion @ Organic-Inorganic Silica Precursor.

Making use of a facile and low-cost way for the preparation of a hierarchically organized novel hollow closed-pore silica antireflective coating (CHAR) with tailored optical properties and a mechanical reliability is of great interest in the field of solar photovoltaic technology. The process mainly contains two aspects: (1) a styrene-acrylate emulsion @ organic-inorganic silica precursor (SA@OISP) core/shell hierarchical nanostructure, consisting of a sacrificial styrene-acrylate (SA) primary template, was fabricated using a sol-gel method; (2) the self-assembly of the nanostructures leads to SA@OISP nanospheres forming the high-quality hollow closed-pore silica antireflection coating (CHAR) by a dip-coating process and a subsequent calcination treatment. The resulting SA@OISP nanospheres have a mean diameter of 65.2 nm and contained a SA soft core with a mean diameter of approximately 54.8 nm and an organic-inorganic silica precursor (OISP) shell with a thickness of approximately 6-10 nm. Furthermore, the prepared CHAR film exhibited a high transmittance and good ruggedness. An average transmittance (TAV) of 97.64% was obtained, and the value is close to the ideal single-layered antireflection coating (98.09%) over a broad range of wavelengths (from 380 to 1100 nm). The CHAR film showed a stable TAV, with attenuation values of less than 0.8% and 0.43% after the abrasion test and the damp heat test, respectively. The conversion efficiency of the CHAR coating cover solar modules tends to be increased by 3.75%. The promising results obtained in this study suggest that the CHAR film was considered as an essential component of the solar module and were expected to provide additional solar energy harvest under extreme outdoor climates.

Preparation of hydrophobic SiO2/PMHS sol and ORMOSIL antireflective films for solar glass cover

Adjusting the porosity of films to obtain a suitable refractive index is one of the key technical concerns of the porous silica antireflective coatings (ARCs) preparation via sol–gel process. However, it is challenging to reduce the refractive index below than 1.20 with the conventional process. In the meantime, residual silanol groups (Si–OH) on coated glasses may deteriorate the weatherability of the ARCs. In this paper, a novel organically modified silicate (ORMOSL) ARCs with good hydrophobicity property and variable refractive index from 1.18 to 1.36 were prepared by modifying the silica sol with polymethylhydrosiloxane (PMHS). In the reaction with PMHS, silica micelle was cross-linked and regrew to synthesize partly clustered ORMOSIL micelle. The ORMOSIL micelles were coated on the soda-lime glasses to form monolayer ARCs. The antireflection and hydrophobicity properties of the coated glasses were significantly improved, i.e., optical transmittance up to 7% gain in the visible range with 130° water contact angle was obtained. Satisfyingly, the SiO2–PMHS sol showed excellent stability with a shelf life of up to 40–105days. In addition, the structure and morphology of the ORMOSIL films were investigated and “Cross-link and fill” model was proposed to explain the effect of PMHS content on the properties of sols and ARCs.

Effect of sol aging time on the anti-reflective properties of silica coatings templated with phosphoric acid

Silica anti-reflective coatings have been prepared by a sol–gel dip-coating process using the sol containing phosphoric acid as a pore-forming template. The effect of the aging time of the sol on the anti-reflective properties has been investigated. The surface topography of the silica AR coatings has been characterized. With increasing sol aging time, more over-sized pores larger than 100nm are formed in the silica coatings. These could act as scattering centers, scattering visible light and thereby lowering transmittance. The optimal aging time was identified as 1day, and the corresponding silica coatings showed a maximum transmittance of 99.2%, representing an 8% increase compared to the bare glass substrate.

Preparation of nanostructure silica antireflective coatings by using sol–gel method

Sol–gel technology is a promising manufacturing method to produce antireflective silica thin films for solar energy applications. So to improve the properties of the films, controlling parameter of the sol–gel method is very important. In this study, soaking treatment effect on optical properties of silica antireflective thin films was investigated. UV–Visible Spectroscopy, Fourier-Transformed Infrared Spectrophotometer and Field Emission Scanning Electron Microscopy was used for the characterization of silica thin films. Results showed that all nanoporous silica layers cause to considerable reduction of light reflections compared with uncoated glasses. With single layer deposition, the amount of reduction depends on the dipping time of coating and has an optimal time. Also, it was found that solar transmittance increased from 91.5% for the bare slide up to 97.5% for the best made sample corresponding to two deposition cycles.