Multilayer Antireflection Coatings Research Articles

Fabrication and characterization of MgF2 anti-reflective films comprising dual-layer prepared by physical vapor deposition technique for optoelectronic applications

Moth eye protuberances, for instance, exhibit highly developed and well-organized nanostructures that allow them to adapt to a wide range of environmental conditions and achieve remarkable antireflective performance, which has inspired and been emulated by scientific advancement. Innovative studies have focused on bioinspired and imitating moth-eye patterns to provide a textured surface in multilayer antireflective coatings (ARC) using nanomaterials, polymers, or composites to eliminate undesired reflection in standard optical components and optoelectronic industrial applications. Multilayer AR systems provide a number of advantages over single-layer designs. Still, their limited applicability is due to obstacles such as mismatched properties at interfaces, high costs, poor mechanical durability, and wetting concerns. Using MgF2 and polytetrafluoroethylene, we develop a technique for fabricating high-performance AR nanostructures on borosilicate crown glass and Fluorine-doped Tin Oxide substrates via the glancing angle deposition technique. By inducing porosity and changing the deposition angle (α) at 550 nm, the refractive index of MgF2 is reduced from 1.38 to 1.14. In agreement with optical modelling predictions, high-performance ARC has been successfully produced on different substrates. Besides this, introducing a thin layer of polytetrafluoroethylene on MgF2 ARC via vapor deposition having a refractive index of 1.21 deposited at α ∼80° results in inducing water-repellent properties in ARC. Hence, our fabricated ARC yields stable AR efficiency with outstanding directional uniformity, durability, and negative temperature stability, having hydrophobic characteristics.

Optimized Wide-Angle Metamaterial Edge Filters: Enhanced Performance with Multi-Layer Designs and Anti-Reflection Coatings

Optimized Wide-Angle Metamaterial Edge Filters: Enhanced Performance with Multi-Layer Designs and Anti-Reflection Coatings

Efficiency enhancement of ultrathin CIGS solar cells by optimal bandgap grading. Part III: piecewise-homogeneous grading

In Parts I [ Appl. Opt. 58, 6067 (2019)APOPAI0003-693510.1364/AO.58.006067] and II [ Appl. Opt. 61, 10049 (2022)APOPAI0003-693510.1364/AO.474920], we used a coupled optoelectronic model to optimize a thin-film CIGS solar cell with a graded-bandgap photon-absorbing layer, periodically corrugated backreflector, and multilayered antireflection coatings. Bandgap grading of the CIGS photon-absorbing layer was continuous and either linear or nonlinear, in the thickness direction. Periodic corrugation and multilayered antireflection coatings were found to engender slight improvements in the efficiency. In contrast, bandgap grading of the CIGS photon-absorbing layer leads to significant enhancement of efficiency, especially when the grading is continuous and nonlinear. However, practical implementation of continuous nonlinear grading is challenging compared to piecewise-homogeneous grading. Hence, for this study, we investigated piecewise-homogeneous approximations of the optimal linear and nonlinear grading profiles, and found that an equivalent efficiency is achieved using piecewise-homogeneous grading. An efficiency of 30.15% is predicted with a three-layered piecewise-homogeneous CIGS photon-absorbing layer. The results will help experimentalists to implement optimal designs for highly efficient CIGS thin-film solar cells.

High-absorption optical stack for aluminum kinetic inductance detectors.

We present a high-absorption optical stack design for aluminum (Al) kinetic inductance detectors (KIDs). Aluminum can be easily processed in micro-fabrication and is the most conventional superconducting material for KIDs. However, it is challenging to achieve high absorption in the Al absorber because of its high reflection at optical wavelengths. By embedding the thin Al film between an anti-reflection (AR) coating layer and a dielectric-based distributed Bragg reflector, we show that close-to-unity absorption can be achieved around a single wavelength (e.g.,≈98.9% at 1518nm). The reflection and transmission measurements agree well with the calculation based on the transmission matrix model. We also show our preliminary results of absorption ≥70% in a broader wavelength range (≈230n m) with multilayer AR coatings. The absorber design in a lumped-element KID is discussed. Our work paves the way to high-efficiency photon-counting and energy-resolving Al-based KIDs in the optical to NIR range.

Comparing single-, double- and triple-layer anti-reflection coatings for ultra-low reflectance in silicon heterojunction solar cells

To increase the efficiency of silicon heterojunction (SHJ) solar cells (SCs), it is paramount to enhance the utilization of sunlight by light management. In this study, the dependences of weighted reflectance and thus generation current (J G) for SHJ SCs on different anti-reflective structures are displayed by OPAL2 simulation tool. According to this, SiN x and SiO2 films are deposited on front of indium tin oxide (ITO) as multilayer anti-reflection coatings (ARCs). It is demonstrated experimentally that the photovoltaic performance of SHJ SCs can be significantly improved by multilayer ARCs. Especially, with 90/21/40 nm SiO2/SiN x /ITO anti-reflective layer structure, the reflectance of SHJ SC is reduced as low as 0.94%, and the current density is shown to be increased by 4.34% compared to the common SCs. This work shows a promising and cost-effective way to achieve higher light utilization and thus promotes photovoltaic characteristics for SHJ SCs.

Fabrication of a porous SiO2 thin film with an ultralow refractive index for anti-reflective coatings

Anti-reflective (AR) coatings are used in various optical products, such as lenses, filters, and transparent conductive films. High-performance multilayer AR coatings can be achieved by reducing the refractive index of the top layer. Preventing light scattering by forming finely structured film is also important for a high-performance antireflection film. In this study, porous SiO2 thin films with ultralow refractive indices were prepared using a simple sol–gel method. A high-quality porous SiO2 thin film with an ultralow refractive index of 1.17 bearing a fine porous structure was fabricated by carefully selecting the solvent and base species. Observation and simulation of the film structure revealed the factors responsible for the low scattering of light and the ultralow refractive index exhibited by the film. Hydrophobic treatment of the film was conducted to reduce the fluctuation of optical performance caused by changes in the refractive index owing to the water adsorbed. Therefore, porous SiO2 thin films can be used in the lenses and filters of various optical instruments.Graphical abstractA transparent film with low refractive index was obtained. The film has porous structure, consisting of silica particles of a few nm in size. The pores size was found to be a few nm by image analysis. Thin films with low refractive index and low scattering for optics were successfully prepared by a simple sol–gel method.

Optimization of Multilayer Antireflection Coatings for Visible and Infrared Regions

Multilayer antireflection coatings have been modeled in visible and infrared regions (1-5 μm) bands to increase the transmittance of glass and silicon substrates. The transmittance was studied using different semiconductor materials with different thickness ( single, double and three) layers to determine the best design that depends on the manufacture of antireflection coatings at low costs and few layers of coatings to reduce the stress generated by the increased number of layers. MgF2 and TiO2 materials are used in the visible region (300-1000 nm) at the central wavelength (500 nm). The transmittance of MgF2 single–layer with a quarter waves optical thickness is reached (98.61%) and the transmittance value is (98.74%) for arrangement (. The transmittance of the infrared spectrum for antireflection coating materials depends on the thickness and temperature of these materials because of scattering and absorption in such materials. LaF3, ZrO2, ZnSe, and CdTe materials are used in the infrared region at a design wavelength (3000 nm). The maximum value of transmittance is around (99.99%) for the best design that consisting of three layers with quarter wavelength thickness. Keywords: Antireflection Coatings, Multilayers, Semiconductor, Transmittance

Simulation of Anti-Reflective TiO2/SiO2 Coating for Silicon Photovoltaic Application by Ray Tracing

n solar systems, anti-reflective coatings are used to reduce reflection and increase efficiency. However, the front surface on the solar cells alone is not effective because most of the light from the sun is reflected and very less energy absorption into the solar cells occur. An anti-reflective coating (ARC) of a sufficient thickness can greatly reduce front surface reflectance. Nanoscale surface texturing, on the other hand, can efficiently capture a higher ratio of incident light to boost optical absorption. In this study, the light trapping scheme within the wavelength of 300 to 1200 nm was used to improve the overall efficiency of silicon solar cells. A thin layer of TiO2 and SiO2 anti-reflective coating with different thicknesses was stacked alternatingly due to their different refractive index with TiO2 having a high refractive index and SiO2 with a low refractive index. Solar irradiance spectrum AM1.5G at normal incidence was used in this present work. For the ray-tracing simulation, the front planar with multilayer ARC with different thicknesses were investigated to obtain the optimum value for optical properties and current density. All the four combination arrangements of SiO2 and TiO2 were evaluated and the maximum potential photocurrent density (Jmax) was calculated. The Jmax value of thin crystalline silicon, c-Si (without ARC) was 24.93 mA/cm2 and increased to 30.28 mA/cm2when ARC was used on the front surface. This represents an increasing of 21.46 % enhancement compared to the Jmax of the c-Si reference. Simulation of Anti-Reflective TiO2/SiO2 Coating for Silicon Photovoltaic Application by Ray TracingImran Al-Haqeem Bin Jaffar1, Siti Hajar Mohmad Salleh2*, Mohd Zaki Mohd Yusoff31,2Faculty of Applied Sciences, Universiti Teknologi MARA, Cawangan Perlis, Campus Arau, 02600 Perlis, Malaysia3Faculty of Applied Science, Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia*Corresponding author’s E-mail: sitiha2902@uitm.edu.myReceived: 08 August 2022 Accepted: 17 February 2023Online First: 17 March 2023

Ameliorating Properties of Perovskite and Perovskite–Silicon Tandem Solar Cells via Mesoporous Antireflection Coating Model

AbstractIt is anticipated that perovskite solar cells (PSCs) will overtake other products in the market for next‐generation photovoltaics. The optical loss, however, continues to be a flaw that restricts the photocurrent (Jph) of PSCs. Mesoporous antireflection coatings (ARCs), both monolayer and multilayer, are designed using a combination of the finite element method and equivalent medium theory, and ARCs models are merged with PSCs. In the current work, mesoporous ARCs are made, the optical performance of the device is evaluated using optical modeling, and then the ARCs are integrated into solar cells. The simulation results show that the Jph of planar inverted PSCs can increase to 24.00 mA cm−2 when the front surface of PSCs adopts mesoporous ARC (via parameter optimization and sensible arrangement and combination). An increase of 0.98 mA cm−2 in Jph of PSCs is observed in comparison with flat ARC (23.02 mA cm−2). The strong light transmission and low reflection properties of the mesoporous ARCs are confirmed by the optimized solution. It is important to note that the first fusion of mesoporous and multilayer ARC offers a fresh approach to the development of perovskite and perovskite/silicon tandem solar cells with extremely high efficiency.

Optical design of multilayer antireflection coatings for indoor solar cell applications.

Multilayer antireflection coatings (ARCs) for solar cells are conventionally designed to enhance the photocurrent level obtained at normal incidence. This is mainly because outdoor solar panels are usually placed such that they can receive strong midday sunlight at a nearly vertical angle. However, in the case of indoor photovoltaic devices, the direction of light changes considerably with changes in the relative position and angle between the device and light sources; therefore, it is often difficult to predict the incident angle. In this study, we explore a method to design ARCs suitable for indoor photovoltaics by essentially taking into account the indoor lighting environment, which is different from the outdoor conditions. We propose an optimization-based design strategy that aims to enhance the average level of the photocurrent generated when a solar cell receives irradiance randomly from all directions. We apply the proposed method to design an ARC for organic photovoltaics, which are expected to be promising indoor devices, and numerically compare the resultant performance with that obtained using a conventional design method. The results demonstrate that our design strategy is effective for achieving excellent omnidirectional antireflection performance and allows the realization of practical and efficient ARCs for indoor devices.

Industrial applications of sol-gel derived coatings.

Sol-gel derived coatings have many practical applications in different industries. In this paper, HI-GARD® hard coat, multi-layer antireflective coatings, and an anti-glare coating with organic particles are described. Optical and mechanical performances of these coatings are discussed in addition to adhesion properties. The HI-GARD® hard coat was dip or spin coated from a sol by hydrolyzing alkoxysilanes with water in an acidic condition. The hard coat acts as a protective coating for optical lenses with excellent optical properties with a Bayer ratio of 4.8 and an adhesion of 5B. The multi-layer antireflective coatings were prepared by incorporating titanium oxide sol into the HI-GARD® hard coat solution to obtain different layers by spin-coating with tunable refractive index. These two-layer or three-layer antireflective coatings increase transmittance by at least 3% compared to an uncoated glass substrate. Anti-glare coatings were spray-coated at room temperature on glass substrates by embedding cationic or anionic polystyrene particles in an acid-hydrolyzed silane sol. The anti-glare coating with organic particles can provide a significant glare reduction with a haze value of up to 13% for display surface without sparkling. In addition to these transparent coatings, non-transparent sol-gel derived coatings such as a sol-gel non-stick coating for cookware and bakeware, and two zinc-silicate protective coatings hydrolyzed from a silane with addition of zinc dusts for corrosion protection are also discussed briefly. The schematic structures of the hard coat on CR-39® substrate, three-layer AR coatings on glass substrate, and organic particle embedded anti-glare coatings on glass substrate, and their respective transmittance or reflective curves.

Broadband Multi-layer Anti-reflection Coatings with Mullite and Duroid for Half-wave Plates and Alumina Filters for CMB Polarimetry

A broadband two-layer antireflection (AR) coating was developed for use on a sapphire half-wave plate (HWP) and an alumina infrared (IR) filter for cosmic microwave background (CMB) polarimetry. Measuring tiny CMB B-mode signals requires maximizing the number of photons reaching the detectors and minimizing spurious polarization due to reflection with an off-axis incident angle. However, a sapphire HWP and an alumina IR filter have high refractive indices of \(\simeq\) 3.1, and an AR coating must be applied to them. Thermally sprayed mullite and Duroid 5880LZ were selected in terms of index and coefficient of thermal expansion for use at cryogenic temperatures. With these materials, the reflectivity was reduced to about 2% at 90/150 GHz and <1% at 220/280 GHz. The design, fabrication, and optical performance evaluation of the AR coatings are described. The coatings were used in a current ground-based CMB experiment called the Simons Array. Also, they could be applied to next-generation CMB experiments, such as the Simons Observatory.

Advanced antireflection for back-illuminated silicon photomultipliers to detect faint light

Silicon photomultipliers have attracted increasing attention for detecting low-density light in both scientific research and practical applications in recent years; yet the photon losses due to reflection on the light-sensitive planar silicon surface considerably limit its photon detection efficiency. Here we demonstrate an advanced light trapping feature by developing the multi-layer antireflection coatings and the textured silicon surface with upright random nano-micro pyramids, which significantly reduces the reflection of faint light in a wide spectrum, from ultraviolet to infrared. Integrating this advanced photon confinement feature into next-generation back-illuminated silicon photomultiplier would increase the photon detection efficiency with significantly lower reflection and much more active areas. This advanced design feature offers the back-illuminated silicon photomultiplier broader application opportunities exemplified in the emerging scenarios such as nuclear medical imaging, light detection and ranging for autonomous driving, detection of scintillation light in ionizing radiation, as well as high energy physics.

Design and optimization of single, double and multilayer anti-reflection coatings on planar and textured surface of silicon solar cells

The present silicon solar cell industry's main concern is to increase efficiency by minimizing the surface reflection. As a result, lately, much attention has been paid to the composition and number of the layers used for anti-reflection coatings in order to reduce surface reflection. In the present work, single, double, triple, and quadruple anti-reflection coatings on silicon solar cells have been designed and optimized using FDTD and PC1D simulation methods. The different combinations of SiO2, SiON, Si3N4, and SiNx coatings on both planar and textured surfaces were simulated and their optical and electrical parameters were investigated. Compared to planar surfaces, the designed coatings on textured surfaces showed better optical and electrical results for almost all investigated parameters. On textured surfaces, SiO2/Si3N4/SiNx acquired the lowest weighted average reflection (0.121%), SiO2/SiNx, SiON/SiNx, SiO2/Si3N4/SiNx, and SiO2/SiON/Si3N4/SiNx the highest Jsc(38.5 mA/cm2) and finally SiO2/Si3N4/SiNx and SiO2/SiON/Si3N4/SiNx both the highest Voc(705.7 mV) and η(23%).

Terahertz antireflection coatings employing off-the-shelf adhesive tapes.

We demonstrate the feasibility of making antireflection coatings (ARCs) for terahertz (THz) light using multilayered polymer films from commercial adhesive tapes. Efficient and low-cost ARCs in the THz range are not conveniently available. Our economical approach can mitigate many of the experimental challenges posed by Fresnel reflection. Harnessing a time-domain THz spectrometer, we demonstrate the performance of several types of multilayer coatings on a variety of substrates. By varying layer stacking and thicknesses, spectral performance can be tuned and optimized for specific applications. Good agreement is found between experimental measurement and analytic calculations evaluating the performance of these multilayer tape ARCs.

Optical Performance Assessment of Nanostructured Alumina Multilayer Antireflective Coatings Used in III-V Multijunction Solar Cells.

The optical performance of a multilayer antireflective coating incorporating lithography-free nanostructured alumina is assessed. To this end, the performance of single-junction GaInP solar cells and four-junction GaInP/GaAs/GaInNAsSb/GaInNAsSb multijunction solar cells incorporating the nanostructured alumina is compared against the performance of similar solar cells using conventional double-layer antireflective coating. External quantum efficiency measurements for GaInP solar cells with the nanostructured coating demonstrate angle-independent operation, showing only a marginal difference at 60° incident angle. The average reflectance of the nanostructured antireflective coating is ∼3 percentage points smaller than the reflectance of the double-layer antireflective coating within the operation bandwidth of the GaInP solar cell (280–710 nm), which is equivalent of ∼0.2 mA/cm2 higher current density at AM1.5D (1000 W/m2). When used in conjunction with the four-junction solar cell, the nanostructured coating provides ∼0.8 percentage points lower average reflectance over the operation bandwidth from 280 to 1380 nm. However, it is noted that only the reflectance of the bottom GaInNAsSb junction is improved in comparison to the planar coating. In this respect, since in such solar cells the bottom junction typically is limiting the operation, the nanostructured coating would enable increasing the current density ∼0.6 mA/cm2 in comparison to the standard two-layer coating. The light-biased current–voltage measurements show that the fabrication process for the nanostructured coating does not induce notable recombination or loss mechanisms compared to the established deposition methods. Angle-dependent external quantum efficiency measurements incline that the nanostructured coating excels in oblique angles, and due to low reflectance at a 1000–1800 nm wavelength range, it is very promising for next-generation broadband multijunction solar cells with four or more junctions.

Performance and durability of thin film solar cells via testing the abrasion resistance of broadband anti-reflection coatings

Reflection from the front glass of solar modules causes over 4% optical loss leading to a significant decrease in module efficiency. Single layer solution gelation (sol-gel) anti-reflective (AR) coatings are effective over a narrow range of wavelengths, whereas reflection losses can be reduced over a broader wavelength when multilayer broadband AR coatings are applied. In this work, three different multilayer AR coatings including 4-layer SiO2/ZrO2, 4-layer SiO2/ITO, and 6-layer SiO2/ZrO2 were deposited using magnetron sputtering. The abrasion resistance is important because the coatings will be subject to regular cleaning cycles. A variety of abraders including Felt pad, CS-10 and CS-8 under different loads are used. The optical performance and durability of these coatings were analyzed using a spectrophotometer, optical microscope, scanning electron microscope, and scanning white light interferometer. No damage was observed after abrasion of the coatings with a felt pad under 1 and 2 N loads. However, there was a slight increase in Weighted Average Reflection. When coatings were tested with CS-10 and CS-8 abraders, coatings with ZrO2 resulted in higher scratch resistance in comparison to coating with ITO. However, all-dielectric broadband AR coatings are more durable and have better optical performance compared to single layer sol-gel coatings.

Laser-induced damage of 1064 nm multilayer antireflection coatings after exposure to gamma rays

Laser coatings designed for space applications not only encounter harsh space environments, but also suffer from laser irradiation. High-energy radiation in space, such as Gamma rays, can cause defects and other damage to materials, which could contribute to laser damage induced by defect absorption. In this work, we studied the optical properties and structural composition of three groups of 1064 nm multilayer antireflection (AR) coatings irradiated by Gamma rays (345 Gy), and the effect of Gamma ray radiation on the laser-induced damage properties of thin films. Experimental results revealed that after exposure to Gamma ray, the absorption and surface roughness of the AR coating increased while the transmittance decreased. X-ray photoelectron spectroscopy (XPS) analysis confirmed that SiO2 is more fragile under Gamma radiation compared to Ta2O5 and HfO2. It was also demonstrated that the Gamma ray damage of AR coatings mainly occurred in the SiO2 layers, and consist of generation of oxygen vacancies and charging defects. The defects generated by Gamma rays increased the absorption of the laser power by the film, hence increasing the probability of laser-induced damage and reducing the laser-induced damage threshold of the film. The coatings prepared by sputtering deposition technique showed lower probability of damage by Gamma ray radiation compared to electron-beam evaporated coatings.

Structural, Morphological, and Optical Properties of Cobalt Oxide Thin Films

AbstractCobalt oxide thin films are successfully synthesized by sol‐gel spin coating method. The XRD study shows that the cobalt oxide thin films annealed at 400°C exhibit cubic polycrystalline structure. SEM images show a well adherent and uniform formation of cobalt oxide thin films with nanosized grains‐like morphology. From the optical study, the direct optical band gap values of as‐deposited and annealed cobalt oxide films are found to lie between 1.42–2.05 and 1.36–1.94 eV. The absorption coefficient of the cobalt oxide is found to be in the order of 104 cm−1. High refractive index of cobalt oxide indicates that it can be used as one of the layers in multilayer antireflection coatings.

Heat-Resistant Black Insulative Thin Films for Flat-Panel Displays in Al-Doped Ag-Fe-O Systems.

Multilayer antireflection (AR) coatings require a material with a large and constant absorption coefficient over the whole visible range and thermal stability. Coatings for use in touch panel displays are also required to be electrically insulative. In this study, 60 mol % Ag-40 mol % (Fe1-xAlx)-O (x = 0, 0.25, 0.50, 0.75, and 1.0) thin films are prepared by pulsed laser deposition, and their optical properties, electric resistance, and thermal stability are clarified by combining the experimental data and density functional theory (DFT) calculations. Over the visible range, large and constant absorption coefficients are obtained for all compositions. The standard deviations of the absorption coefficients of the x = 0.75 and 1.0 samples are found to be smaller than those of conventional materials like graphite and CrOx. High sheet resistance (Rsheet > 107 Ω·sq-1) is also confirmed. It is determined that nanometer-sized Ag dispersed into a matrix, which was confirmed to be ionic Ag in the matrix phase, is responsible for the absorption at a shorter visible light range and insulative nature even at high Ag content. The films with high Al content are stable up to 500 °C. The potential of these black insulative Ag-Al-Fe-O thin films for use as black AR coatings is confirmed by optical simulations with multilayer stacks.