Antireflective Films Research Articles

High Refractive Index Diphenyl Sulfide Photopolymers for Solar Cell Antireflection Coatings

The anti-reflection film can effectively reduce the surface reflectivity of solar photovoltaics, increase the transmittance of light, and improve the photoelectric conversion efficiency. The high refractive index coating is an important part of the anti-reflection film. However, the traditional metal oxide coating has poor stability and complicated processes. To address this issue, we prepared two organic high refractive index (HRI) photopolymers by modifying epoxy acrylic acid with 4,4′-thiodibenzenethiol, which can be surface patterned by nanoimprinting to prepare antireflection coatings. As a result, two modified photopolymers with high refractive index (n > 1.63), high optical transmittance (T > 95%), and thermal stability (Tg > 100 °C) are obtained after curing. In particular, the diphenyl sulfide photopolymer modified by ethyl isocyanate acrylate has a refractive index up to 1.667 cured by UV light. Our work confirms that the organic HRI photopolymer can be obtained by introducing high molar refractive index groups, with potential to be applied as a PV cell power conversion efficiency material.

High performance of broadband anti-reflection film by glancing angle deposition

This study reports that SiO2 was selected to fabricate broadband anti-reflection (AR) films on fused silica substrates by using glancing angle deposition and substrate rotation. Through accurate control of the graded index of the SiO2 layer, the average residual reflectance of the graded broadband AR film can achieve an average value of 0.59% across a spectral range of 400-1800nm. By comparing the performance, the broadband anti-reflection film with substrate speed has higher stability compared with the broadband anti-reflection film without substrate speed and a higher damage threshold than the traditional anti-reflection film.

Scalable deposition of sol–gel based monolayer antireflective thin films by using a dual alkoxysilane precursor chemistry

Scalable deposition of sol–gel based monolayer antireflective thin films by using a dual alkoxysilane precursor chemistry

Omnidirectional and broadband photon harvesting in self-organized Ge columnar nanovoids

Highly porous Germanium surfaces with uniformly distributed columnar nanovoid structures are fabricated over a large area (wafer scale) by large fluence Sn+ irradiation through a thin silicon nitride layer. The latter represents a one-step highly reproducible approach with no material loss to strongly increase photon harvesting into a semiconductor active layer by exploiting the moth-eye antireflection effect. The ion implantation through the nitride cap layer allows fabricating porous nanostructures with high aspect ratio, which can be tailored by varying ion fluence. By comparing the reflectivity of nanoporous Ge films with a flat reference we demonstrate a strong and omnidirectional reduction in the optical reflectivity by a factor of 96% in the selected spectral regions around 960 nm and by a factor of 67.1% averaged over the broad spectral range from 350 to 1800 nm. Such highly anti-reflective nanostructured Ge films prepared over large-areas with a self-organized maskless approach have the potential to impact real world applications aiming at energy harvesting.

In situ plasma cleaning of large-aperture optical components in ICF

The organic contamination damage of large-aperture optical components limits laser energy improvement of inertial confinement fusion (ICF). In situ cleaning of large-aperture optical components via low-pressure plasma is expected to remove organic contaminants from the optical surface. Herein, low-pressure air plasma equipment was proposed and used on surfaces of SiO2 sol–gel antireflection (AR) films in situ by conducting experiments. Its electrical discharge parameters were investigated and optimized during plasma cleaning. Plasma diffusion characteristics and homogeneity in large-aperture windows were analyzed by optical emission spectroscopy. Dramatic degradation in the optical properties of components was observed after organic contamination for 5 h. Transmittance, laser-induced damage threshold and surface morphology observation results demonstrated that low-pressure air plasma removed the organic contaminants from the surface of sol–gel AR films without causing damage and metal contamination. After plasma cleaning, the hydrophilicity of the films increased significantly due to the increase in the polar components of surface free energy. The mechanism of plasma cleaning organic contaminants was confirmed by x-ray photoelectron spectroscopy measurements. These salient results provide a new alternative method for removing organic contaminants in situ from large-aperture optical components and a foundation for improving the energy output of the ICF system.

Preview the Products on Display at Display Week 2022

Preview the Products on Display at Display Week 2022

Resonance-Enhanced Quantum Well Micropillar Array with Ultra-Narrow Bandwidth and Ultra-High Peak Quantum Efficiency

Infrared cameras with narrow-band detection capability are widely used for SF6 gas detection, which is an essential part of power equipment inspection. Narrow-band detection is usually achieved by a combination of quantum well infrared photodetectors (QWIPs) and narrow-band filters. Improving the quantum efficiency of QWIPs and reducing the detection bandwidth are important ways to improve camera performance. In this study, a back-incident-type device of quantum well micropillar array targeting at a 10.5 μm central wavelength is designed and studied by three-dimensional simulation. The operating mechanism of the device was determined by investigating the effect of the device geometry on the quantum efficiency. The enhanced absorption capability of the device mainly comes from the Fabry–Pérot resonance and the antireflection effect. The final device exhibits a remarkable peak quantum efficiency of 83% at 10.5 μm and an ultra-narrow spectral bandwidth of 0.2 μm. These excellent properties are achieved without an antireflective film and narrow-band filter, which can significantly improve the narrow-band capability and integration of the system; the dark current reduces to be 0.2762 times due to the low-duty cycle. These properties indicate that the structure of the quantum well micropillar array is of great significance to the development of QWIPs used in gas detection.

Ferroelectric crystals with giant electro-optic property enabling ultracompact Q-switches.

Relaxor-lead titanate (PbTiO3) crystals, which exhibit extremely high piezoelectricity, are believed to possess high electro-optic (EO) coefficients. However, the optical transparency of relaxor-PbTiO3 crystals is severely reduced as a result of light scattering and reflection by domain walls, limiting electro-optic applications. Through synergistic design of a ferroelectric phase, crystal orientation, and poling technique, we successfully removed all light-scattering domain walls and achieved an extremely high transmittance of 99.6% in antireflection film-coated crystals, with an ultrahigh EO coefficient r33 of 900 picometers per volt (pm V-1), >30 times as high as that of conventionally used EO crystals. Using these crystals, we fabricated ultracompact EO Q-switches that require very low driving voltages, with superior performance to that of commercial Q-switches. Development of these materials is important for the portability and low driving voltage of EO devices.

Near 90% Transparent ITO-Based Flexible Electrode with Double-Sided Antireflection Layers for Highly Efficient Flexible Optoelectronic Devices.

As a widely used substrate for flexible electronics, indium-tin oxide-based polymer electrodes (polymer-ITO electrodes) exhibit poorly visible light transmittance of less than 80%. The inferior transmittance for polymer-ITO electrodes severely limits the performance improvement of polymer-ITO based electronics. Here, a conceptually different approach of the double-sided antireflection coatings (DARCs) strategy is proposed to modulate both the air-polymer substrate interface and ITO-air interface refractive index gradient, to synergistically improve the transmittance of polymer-ITO electrodes. On the basis of SiO2 nanoparticles antireflection layer on polymer substrate, a polymer-metal oxide composite antireflection film is fabricated on the ITO side. Resultantly, the transmittance of ITO-based flexible electrodes is successfully improved from 76.8% to 89.8%, which is the highest transmittance among the reported ITO-based flexible electrodes. Furthermore, the photoluminescence emission intensity of luminescent materials enveloped with the DARCs electrodes increases by 74% over that with reference electrodes, demonstrating the DARCs antireflection strategy can efficiently improve the performance of flexible optoelectronic devices. With DARCs electrode, the flexible perovskite solar cells exhibit an enhanced efficiency from 18.80% to 20.85%.

Resilient moth-eye nanoimprinted antireflective and self-cleaning TiO2 sputter-coated PMMA films

Moth-eye nanostructures are amongst the most remarkable surfaces in nature because of their multi-functionality including antireflection, self-cleaning and bactericidal ability. Moth-eye surfaces consist of subwavelength arrays of tapered nanostructures, which are challenging to reproduce artificially. Nanoimprint lithography is probably one of the most suited technologies for this purpose. However, the poor mechanical resilience and durability of the polymeric nanocones when exposed to the environment, hinders their use in actual applications. To overcome these limitations, this work demonstrates the use of a thin oxide coating over the polymer moth-eye features imprinted on poly methyl methacrylate (PMMA) films. Particularly TiO2 conformal thin film coatings are deposited by unipolar pulsed dc magnetron sputtering over the antireflective nanopatterns acting as encapsulant. The coating, while preserving the antireflective properties, protects the nanostructures against mechanical scratching and improves substantially their thermal stability to over 250 °C. Furthermore, the TiO2 layer provides additional photoinduced self-cleaning functionality and at the same time it protects the matrix from UV photodegradation. The robust and durable antireflective surfaces developed here may find application on solar cells covers, flat panel displays or on optical components.

Fabrication of Cu/Cu2O/CuO@WO3 composite films with antireflective, hydrophilic, and photocatalytic properties by magnetron sputtering

Multifunctional coated glass with antireflective, hydrophilic, and photocatalytic properties was prepared by magnetron sputtering. Cu/WO3 bilayered structures were deposited on the glass surface, and Cu and its oxide-loaded WO3 composite thin films were obtained by annealing at 574 K, 674 K, 774 K, and 824 K. The effects of micro-characteristics on antireflective, hydrophilic, and photocatalytic properties were investigated to obtain the best composite. The density and reflectivity of the films were reduced by changing the annealing temperature. The composite film annealed at 774 K had the highest transmittance of 85% at 629 nm. Moreover, the annealed Cu/Cu2O/CuO@WO3 films manifested excellent hydrophilic properties due to the formation of large agglomerated structures on their surfaces. Cu and its oxides were loaded with WO3 to obtain Z-type heterojunctions and plasma resonance, which greatly improved the photocatalytic efficiency of the films. The photocatalytic degradation rate of the composite films reached 2.3 × 10-−2 min−1, which was 3–4 times larger than that of the pure WO3 film. Therefore, this study provides new possibilities for the preparation of antireflective and self-cleaning thin films with high efficiency and low cost.

Antireflective, Transparent, Water-Resistant, and Antibacterial Zn-Doped Silicon Oxide Thin Films for Touchscreen-Based Display Applications

Antireflective, Transparent, Water-Resistant, and Antibacterial Zn-Doped Silicon Oxide Thin Films for Touchscreen-Based Display Applications

Texturing of polydimethylsiloxane surface for anti-reflective films with super-hydrophobicity in solar cell application

This study utilized a Cu metal assisted chemical etching (MACE) method to produce an anti-reflection texture on poly dimethyl siloxane (PDMS). We measured the diffuse and total transmittance, total reflectance, and haze ratio to analyze the optical properties of the textured PDMS films, which were confirmed using finite-difference time-domain (FDTD) calculations. The anti-reflection textured PDMS films exhibited improved optical performance in the visible light region, owing to the light scattering and trapping effect, by improving the lateral surface area and aspect ratio of the micro/nanostructures. The average reflectance was 2.86% under optimal conditions. The optimized structures of the films also showed super-hydrophobicity (θCA≈155.2°). We applied the optimized film to perovskite photovoltaic solar cell devices and observed an enhanced short-circuit current density (Jsc) from approximately 21.95 to 24.06 mA/cm2 (∼9% increase). The improved Jsc increased the PCE to 17.11% (∼11% increase) in the MAPbI3 p-i-n structured devices. Based on the results, we confirmed that the superhydrophobic anti-reflection PDMS film can be used to overcome the limitation of light absorption in solar cell applications.

UV-cured organic–inorganic composites for highly durable and flexible antireflection coatings

In this work, we develop novel UV-cured composite antireflection films by using UV curable silsesquioxanes (GPOSS) as the organic network and acidic silica sols as the inorganic parts. The composite films can be rapidly crosslinked and solidified under UV light and UV ozone exposure, respectively. The final coatings exhibit broadband antireflective properties with average transmittance of 92.71% from 400 nm to 2000 nm, and the coatings display mechanical robustness with relative transmittance reduced of only 0.38% and 0.08% after cyclic scrubbing and tape-peeling tests. Due to synergetic effect from vigorous organic-organic intramolecular crosslinking and delicate organic–inorganic intermolecular crosslinking, the coatings achieve good environmental durability with negligible optical loss after 48 h HAST test. By this design, the present UV cured composites pave the way to select novel functional materials for robust flexible antireflection use. And the method in this work opens up prospective opportunities for large-scale, flexible, and rapid coating preparation with multiple performances, which can be used to transparent displays and various flexible opto-electronic devices.

Preparation of SiO2 antireflection film with high hardness and adhesion by mPEG

Coating antireflection film on the surface of glass cover is one of the important methods to improve the photoelectric conversion efficiency of solar cells. Sol-gel method is suitable for low cost and large area preparation of antireflection film. However, most of antireflective films prepared with sol-gel have not enough good mechanical properties, and their applications are restricted. A porous antireflection film was prepared with sol-gel, where the polyethylene glycol monomethyl ether (mPEG) was used as the porogen. The effects of the mPEG additive amount were investigated on the microstructure and properties of the film. The results showed that the transmittance of the film (the coated glass) first increases and then decreases with the increase of the amount of mPEG. When the amount of mPEG is 0.6 g, the average transmittance of the film in the wavelength range of 380–1100 nm is the highest, higher than that of glass substrate by 4.2 percentage points. The adhesion of the film reaches grade 0 and the hardness is greater than 9H. The efficiency of monocrystalline silicon solar cells could be increased from 11.65% to 12.04%, by a relative increase of 3.35%

Study on the Effect of Anti-Reflection Film on the Spectral Performance of the Spectral Splitting Covering Applied to Greenhouse

Study on the Effect of Anti-Reflection Film on the Spectral Performance of the Spectral Splitting Covering Applied to Greenhouse

Meniscus and Spin Coating Methods for Coating SiO2 Sol-Gel Antireflective Film on Beam Sampling Grating

Meniscus and Spin Coating Methods for Coating SiO2 Sol-Gel Antireflective Film on Beam Sampling Grating

Long-lasting antifogging mechanism for large-aperture optical surface in low-pressure air plasma in-situ treated

In this article, the long-lasting antifogging capability of large-aperture optical components was obtained by the in-situ plasma treatment. Water contact angle and surface free energy were used to study the overall antifogging evolution of optical components in the air. The optical performance, including laser-induced damage threshold and surface morphology, were discussed after plasma cleaning. Elements contents and functional groups information were analyzed by X-ray photoelectron spectroscopy detection as a reference to simulation results. In molecule dynamics simulations, the substrates of fused quartz were modified by linking various functional groups (-H, –OH, –CHO, –COOH, –NH2) to simulate the surface of optical components after plasma treatment at a microscopic level. Experimental results showed that the surface of the optical components (fused quartz, sol-gel antireflection film, multilayer dielectric film) treated by plasma had a good antifogging effect, which can be maintained for 300 min. The surface wettability of optical components was improved significantly after plasma treatment, which was supported mainly by the polar components in the surface free energy. Besides, The optical performance of the components was enhanced while the surface structure was barely damaged. According to simulation results, it was found that –CHO, –COOH, and –NH2 played a dominant role in improving the hydrophilicity of optical components, compared with -H, –OH. The hydrophilic surfaces after plasma modification were obtained because more hydrogen bonds were generated between the surface functional groups and the water molecules. The above research provides a new method and a theoretical basis for improving the long-lasting antifogging for large-aperture optical components.

Effects of O2 flux on structure, optical properties and hydrophobicity of highly emissive antireflective HfO2 thin films by magnetron sputtering

We used magnetron sputtering to prepare high emissive HfO2 thin films with thickness 300–500 nm under different O2 flux. A dense uniform HfO2 thin film with a polycrystalline monoclinic structure had been achieved. The effects of O2 flux on structural, optical and mechanical properties of deposited thin films were investigated. With the increasing O2 flux, the thickness of both the thin film and HfSixOy interlayer found at the interface of HfO2 and Si substrate decreased while the grain size and surface roughness increased significantly. At an O2 flux of 30 sccm, the deposited HfO2 film achieved a high transmittance up to 93%, a high emissivity up to 90%, a low bandgap (5.65 eV), a high refractive index (2.03) and a good hydrophobicity with an optimum contact angle of 117.8°. The obtained results of high emissivity, optical transmission and hydrophobic behavior are best among the reported performance, with the implication for application in high-performance optical coatings of lenses, windshields and optoelectronic devices.

Highly transparent antireflection coatings on fullerene-free organic solar cells using polymeric nanoparticles

A simple method is described herein for the preparation of highly transparent antireflection (AR) coatings based on polymeric nanoparticles (NPs) for efficient organic solar cells. The NPs based on poly(styrene-co-acrylic acid) (PS-co-PAA) are synthesized via a straightforward emulsion polymerization process, and air void-containing AR films are deposited onto the glass sides of organic solar cells via spin-casting of the NP solution. Various NP sizes ranging from 42 to 86 nm are used to provide a variety of pore fractions and refractive indices. The AR film with an average particle size of 86 nm is shown to increase the normal-incident 595-nm light transmittance from 92.0 to 98.9%. The AR coatings on solar cells are beneficial for the light absorption of the photoactive layers, thus resulting in enhanced short-circuit current densities of up to ∼26.8 mA cm-2. The power conversion efficiency of the device with the optimum AR coating is increased to 12.8% compared to that of non-AR device (12.0%). This work represents a simple strategy for developing high-performance solar cells.