Transmittance Of Glass Substrate Research Articles

Moth-eye-like antireflection coatings based on close-packed solid/hollow silica nanospheres

Broadband antireflection coatings (ARCs) attract increasing attentions due to the effective reduction of reflection between the interface of air and substrates over a broad range of wavelengths. Moth-eye-like array ARCs with high antireflection performance have been successfully fabricated via a facile and low-cost sol–gel method using solid silica nanospheres (SSNSs) and hollow silica nanospheres (HSNSs). The composite of SSNSs and HSNSs was closely arranged on the glass substrate to firstly construct the close-packed solid/hollow silica nanospheres (c-S/HSNSs) array, in which HSNSs were used to regulate the refractive index and many triangular grooves among adjacent nanospheres were formed. Then moth-eye-like array structure was obtained by locating the nanospheres on the groove positions in c-S/HSNSs array. The transmittance of glass substrates with moth-eye-like array structure has been increased from 91.0% to 99.0%, with an average solar transmittance of 97.8%. The reflection of glass substrates with moth-eye-like array structure was prominently reduced in wide-angle incidence, and the minimum reflectance changed from 0.17% to 1.34% within 8 to 60°. The moth-eye-like array structure exhibits the high antireflection performance and excellent thermal stability and is promising in photovoltaic modules, optical lenses, and other outdoor applications.

Effect of Different TiO2-SiO2 Multilayer Coatings Applied by Sol-Gel Method on Antireflective Property

Multilayer thin films prepared using the sol-gel process have been used in many antireflection applications. In this paper, antireflective nanoscale multilayer TiO2-SiO2 coatings were formed on both sides of the glass substrates by combining sol-gel method and dip coating techniques. The coatings were carried out using tetraethyl orthosilicate as precursor for SiO2 and tetrabutyl orthotitanate as precursor for TiO2. The coatings prepared in this work were characterized using scanning electron microscope, Fourier-transformed infrared spectrophotometer and UV-Visible spectrophotometer. The SiO2 top layer coatings showed excellent antireflection in the wavelength range of 400-800 nm where the transmittance of glass substrate is significantly lower. By increasing the number of double TiO2-SiO2 layers, the transmission of the coated glasses increased due to applied multilayer coating properties. Six-layer sol-gel TiO2-SiO2 coatings showed the highest visible transmittance about 99.25% at the band of 550-650 nm.

Preparation of Anti-reflection Coatingswith Hollow Silica Nanoparticles by Self-assembly

Using tetraethyl orthosilicate (TEOS) as raw material and polyacrylic acid (PAA) as nucleating material, hollow silica nanoparticles were synthesized on the basis of traditional method of Stober. Using hollow silica nanoparticles, both single-layer anti-reflection coatings and broad-band double-layer anti-reflection coatings were prepared by self-assembly. The structure control of the hollow silica nanoparticles, the effect of deposition cycle, pH value of the hollow silica nanoparticle dispersion on transmittance of coatings, and the preparation of the double-layer anti-reflection coatings with a graded-refractive-index were investigated. The results show that the size and void fraction of the hollow silica nanoparticles can be controlled precisely by changing the amount of PAA and TEOS. The thickness and refractive index of the anti-reflection coatings can also be tuned accurately in the same way. The deposition cycles are reduced from 10 cycles to 2 cycles by acid pickling which simplifies the coating process. This new technique significantly increases the transmittance of glass substrate coated by single-layer anti-reflection coatings in the range of 350–800 nm under optimum conditions, and improves the maximum transmittance from 91.6% to 98.1% at optimized wavelength (λ=520 nm). Furthermore, glass substrate coated by double-layer anti-reflection coatings can increase the transmittance more than 5% in a much wider wavelength range 948 无 机 材 料 学 报 第 29卷 (400–1500 nm).

A facile dip-coating approach based on three silica sols to fabrication of broadband antireflective superhydrophobic coatings

This paper reports a new design to fabricate broadband antireflective superhydrophobic coatings by versatile dip-coating of three silica-based sols: silica sol (below 10nm) prepared under acidic conditions (sol A), silica nanoparticle (ca. 25nm) suspension prepared by the Stöber method (sol B) and mesoporous silica nanoparticle (MSN) suspension, followed by chemical vapor deposition of 1H,1H,2H,2H-perfluorooctyltriethoxysilane. The maximum transmittance of coatings reached as high as 95.3% at the wavelength of 630nm, whereas the water contact angle was 153° with sliding angle ⩽5° by applying of the A2/B/MSN2 coating. The superhydrophobic A/B/MSN2 coating (water contact angle: 153°, sliding angle: ⩽5°) showed excellent antireflection in the wavelength range of 400–2000nm, especially in the wavelength range of 742–1573nm where the transmittance of glass substrate is significantly lower. Transmission electron microscopy was used to characterize the morphology of synthesized nanoparticles. Scanning electron microscopy and atomic force microscopy were used to observe the morphology and estimate the surface roughness of coatings. Optical properties were characterized by a UV–visible–near infrared spectrophotometer. Surface wettability was studied by a contact angle/interface system. The broadband antireflection of superhydrophobic A/B/MSN2 coating was discussed in detail.

Graded porous glasses for antireflective applications formed by chemical treatment

Porous glass surface can be achieved by the neutral-solution etch process, which has been reported to be effective in suppressing light reflection from glasses. Samples of a commercial borosilicate glass were submitted to a static aqueous corrosion at 87°C for several hours for introducing porosity on glass surface. Morphology, composition and optical properties of the surface, which were analyzed by scanning electron microscope (SEM), energy dispersive spectrum (EDS) and spectrometer, can be controlled by changing both the neutral-solution concentration and etching time. The results show that the transmittance of glass substrate can be improved after chemical treatment, and the laser-induced damage threshold of graded porous glass is much higher than that of antireflective coatings. The SEM and EDS results revealed a significant corrosion process in the solution, and determined the relationship between the graded porosity and refractive index of glasses.

Imprinted Moth-Eye Antireflection Patterns on Glass Substrate

Sub-micron sized, conical shaped moth-eye structure was transferred to thermoplastic polymer film, such as polyvinyl chloride (PVC) using hot embossing process. Since master template was made of polycarbonate, embossing temperature and pressure were carefully maintained to 100°C and 10 atm. Conical shaped moth-eye pattern was reversed to tapered hole pattern on PVC film. Hot embossed PVC film was then used as transparent template for subsequent UV nanoimprint process, in order to form the conical shaped sub-micron moth-eye structure on glass substrate. After thin layer of Si oxide and monolayer of self-assembled, silane based molecules was coated on hot embossed PVC film. UV nanoimprint process was done on the glass substrate using hot embossed PVC film. As a result, the transmittance of glass substrate was increased from 91 to 94% for single side patterned and 96% for both side patterned glass substrate for the spectral range of 350 to 800 nm.