Design Of Antireflection Coatings Research Articles

Design of Broadband and Wide-angle HLHL Antireflective Coatings for Triple Junction Solar Cells

Design of Broadband and Wide-angle HLHL Antireflective Coatings for Triple Junction Solar Cells

Novel Deposition Method of Crosslinked Polyethylene Thin Film for Low-Refractive-Index Mid-Infrared Optical Coatings.

Mid-infrared optics require optical coatings composed of high- and low-refractive-index dielectric layers for the design of optical mirrors, filters, and anti-reflection coatings. However, there are not many technologies for depositing a material with a refractive index of less than 2 and a low loss in the mid-infrared region. Here, we present a unique deposition method of crosslinked polyethylene thin film for mid-IR optical filter design. Polyethylene has a refractive index of 1.52 in the mid-infrared region and a small number of absorption peaks, so it is useful for making optical filters in the mid-infrared region. Only 1 keV of energy is required to crosslink the entire film by irradiating an electron beam while depositing polyethylene. In addition, crosslinked polyethylene thin film has high mechanical strength, so there is no cracking or peeling when used with germanium. This allows for the use of crosslinked polyethylene as a low refractive index for mid-infrared optical coating.

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.

Anti-reflection coatings for epsilon-near-zero materials

Epsilon-near-zero (ENZ) materials have attracted much interest within the photonics community due to the various novel light-matter interactions that can occur in the ENZ regime. These materials display a large impedance mismatch between the ENZ material and free space, making it difficult to couple light into the medium at normal incidence. In this article, we demonstrate that enhanced light coupling into an ENZ metamaterial stack can be achieved via the design and fabrication of anti-reflection coatings, which are simple to fabricate via e-beam evaporation. The coating fabricated has been optimized not only to minimize reflection but also aims to maximize transmission — making these designs applicable to e.g. beam shaping applications. We achieve a transmission enhancement of 20% through our metamaterial over a 150 nm range and reflection minimization of 50% over a 200 nm range.

Optical and mechanical properties of Zr-oxide doped TiO2/SiO2 anti-reflective coatings for PV glass covers

Multi-layer systems are frequently used as anti-reflective coatings (ARCs) due to their excellent optical properties. However, these systems suffer from erosive degradation (wear), thus urgently seeking alternative ways to improve their mechanical properties while maintaining their optical response. To tackle this problem, we propose to dope multi-layer TiO 2 /SiO 2 coatings with Zr-oxides to enhance their crystalline structure and density/compactness, as well as to form Si–Zr–O bonds. We explore the effect of Zr-oxide doping on the microstructure as well as the optical and mechanical properties of multi-layer TiO 2 /SiO 2 coatings with the overall aim to synergistically induce enhanced optical and mechanical properties. Therefore, homogeneous 250 nm thick multi-layer TiO 2 /SiO 2 coatings doped with Zr-oxides (different atomic concentrations) were deposited on glass substrates by magnetron sputtering. Based on our analysis, Zr-doping improves the optical and mechanical properties simultaneously. Among all ARCs, the sample annealed at 400 °C and doped with 1 at.-% Zr presented an excellent anti-reflective behavior and the best mechanical performance. These characteristics point towards an improved mechanical resistance (outstanding durability) and optical efficiency thus rendering them excellent candidates for the protection of glass covers on solar panels. • Design of anti-reflective coatings with TiO 2 /SiO 2 multi-layers doped with Zr-oxides. • Assessment of mechanical properties via XPM ultra-fast nanoindentation. • Zr-oxide doping and annealing synergistically improved mechanical properties.

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%).

Anti-fog nanocomposite coatings of enhanced durability

Highly porous nanocomposite films were produced at room temperature from SiO2 or TiO2–SiO2 solutions synthesized by a sol–gel route in the presence of oxide nanoparticles. The photocatalytic behavior of titania-based films was controlled at the sol synthesis step, through three parameters: the relative molar concentration between polymeric and condensed silica, the reactivity of the hydrolysis step, and the relative molar concentration of the active component. The reported method allowed ample tuneability of film refractive index, an important parameter for the design of antireflective and multifunctional coatings. Superhydrophilic properties were demonstrated by the samples and, notably, retained for over 30 days. Experimentally mimicking accelerated surface pollution with olive oil and stearic acid, a strong correlation was found between residual organic contamination, quantified by integrating the film absorption FT-IR spectrum over the C–Hn stretching area, and the measured water contact angle (WCA). Strategies for a fast surface cleaning and restoration of the superhydrophilic behavior via a mild oxidizing agent, based on UV exposure or immersion in a NaClO water solution, were investigated.High wettability can also be obtained through the control of the porosity. This effect has been termed nanowicking: the rapid infiltration of water in an interconnected porous network.

Antireflective Self-Cleaning TiO2 Coatings for Solar Energy Harvesting Applications

Titanium(IV) oxide (TiO2, titania) is well-known for its excellent photocatalytic properties, wide bandgap, chemical resistance, and photostability. Nanostructured TiO2 is extensively utilized in various electronic and energy-related applications such as resistive switching memory devices, flat panel displays, photodiodes, solar water-splitting, photocatalysis, and solar cells. This article presents recent advances in the design and nanostructuring of TiO2-containing antireflective self-cleaning coatings for solar cells. In particular, the energy harvesting efficiency of a solar cell is greatly diminished by the surface reflections and deposition of environmental contaminants over time. Nanostructured TiO2 coatings not only minimize reflection through the graded transition of the refractive index but simultaneously improve the device’s ability to self-clean and photocatalytically degrade the pollutants. Thus, novel approaches to achieve higher solar cell efficiency and stability with pristine TiO2 and TiO2-containing nanocomposite coatings are highlighted herein. The results are compared and discussed to emphasize the key research and development shortfalls and a commercialization perspective is considered to guide future research.

Design and preparation of superhydrophobic, broadband and double-layer antireflective coatings

As one of the most widely used optical films, antireflective coating (ARC) is widely used in lasers, display screens and solar cells. In this article, the double-layer ARC coating consists of a bottom layer using SiO2-TiO2 composite nanomaterials and a top layer of SiO2 modified with Hexamethyldisilazane (HMDS). The optimal parameters of the double-layer ARC were obtained through the simulation software Macleod. Meanwhile, the aging time of SiO2 sol, the volume fraction of HMDS, the annealing temperature, the dip-coating speed, and the volume fraction of TiO2, which affect the refractive index of the bottom and top layers, were explored in order to match the best parameters. By adjusting the structure of the bottom and top layers, the double-layer broadband ARC coating has a maximum transmittance of 97.6% in the 400-1800 nm spectral range, and an average transmittance of 96.0%. In addition, HMDS was used to modify the SiO2 sol to obtain a double-layer ARC with superhydrophobic properties with a hydrophobic angle of 151.4°. After the high-temperature and high-humidity environment test, the antireflective performance of the double-layer ARC has not changed significantly, demonstrating the broad prospects for application in large outdoor solar photovoltaic power plants. Moreover, this work not only provides a new method for adjusting the refractive index of the coating, but also opens up a new way for the preparation of broadband ARC.

Design of Anti-Reflection Coatings for Application in the Infrared Region (10.6 micron)

In this research, anti-reflection coatings consisting of single and double layers were designed in the IR (8 – 14μm) region to reduce the unwanted reflections of germanium (Ge) substrate. The reflectance of Ge substrate was about 36% per surface. These values were reduced reasonably by using single and double layer anti-reflection. The used layers were promoted in their performance by changing their thickness and refractive indices. The results indicated that the suggested structures are very efficient in reducing the reflectance of the Ge substrates in the selected region. The performance of the double layer antireflection coatings of ZnSe, BaF2 and BiF3 on Ge substrates is presented.

Evolutionary algorithms converge towards evolved biological photonic structures

Nature features a plethora of extraordinary photonic architectures that have been optimized through natural evolution in order to more efficiently reflect, absorb or scatter light. While numerical optimization is increasingly and successfully used in photonics, it has yet to replicate any of these complex naturally occurring structures. Using evolutionary algorithms inspired by natural evolution and performing particular optimizations (maximize reflection for a given wavelength, for a broad range of wavelength or maximize the scattering of light), we have retrieved the most stereotypical natural photonic structures. Whether those structures are Bragg mirrors, chirped dielectric mirrors or the gratings on top of Morpho butterfly wings, our results indicate how such regular structures might have spontaneously emerged in nature and to which precise optical or fabrication constraints they respond. Comparing algorithms show that recombination between individuals, inspired by sexual reproduction, confers a clear advantage that can be linked to the fact that photonic structures are fundamentally modular: each part of the structure has a role which can be understood almost independently from the rest. Such an in silico evolution also suggests original and elegant solutions to practical problems, as illustrated by the design of counter-intuitive anti-reflective coatings for solar cells.

Broadband antireflective coatings for high efficiency InGaP/GaAs/InGaAsP/InGaAs multi-junction solar cells

Design and fabrication of antireflection coatings (ARCs) was performed to maximize the photocurrent of Ⅲ-Ⅴ solar cells based on InGaP, GaAs, InGaAsP, and InGaAs. The current-limiting behavior of multi-junction solar cells allowed only the specific design of ARCs to improve the total current density of multi-junction solar cells, which enabled thin and efficient antireflection layers to achieve their full potential. ARCs were designed for InGaP/GaAs and InGaAsP/InGaAs double junction solar cells and InGaP/GaAs/InGaAsP/InGaAs quadruple junction solar cells. From the ARC design results, the best solar cell reflectance at the region of interest appeared to be 1.44% for InGaP/GaAs solar cells, 2.17% for InGaAsP/InGaAs, and 0.48% for the quadruple junction solar cells. To achieve the preferred refractive index for the ARC structures, nanostructures fabricated via glancing angle deposition were utilized. With ARC fabricated structures, InGaP/GaAs double junction solar cells yielded a power conversion efficiency of 13.3%, which was 1.34 times higher than that of cells without ARC (9.91%). Additionally, calculation results for the various ARC designs using dual and triple material systems were provided to increase their applicability.

Design, preparation and characterization of antireflective coatings using oxynitride films

In present paper, we introduce an investigation of aluminum oxynitride films deposition using one metallic target in various gas mixture. The optimized preparation conditions for such reactive sputtering were found. Non-optimized conditions led to sputtering target poisoning or under-stoichiometric films formation. The reactive deposition process was guided by the active feedback control system. Dependence between gas composition and changes of nitrogen concentration in the films and their optical properties were investigated. The increase of nitrogen content in films leads to increases in extinction coefficient in UV region and refractive index in the whole investigated wavelength range. It was shown the possibility of using oxynitride films for antireflective coating (AR) deposition. The coating composed from three layer of oxynitrides with changing the composition. It has low surface roughness and low compressive stress.

Fabrication of absorbing Nb-Ti suboxide anti-reflective thin film stacks

Optically black anti-reflective coatings that absorb light are potentially useful for color isolation in the flat panel display industries and stray light reduction in imaging technologies. Here we report the design and fabrication of high performance multilayered black anti-reflective coatings. Thin film suboxides NbxTi1−xO2, NbO2 and TiO2−x were prepared using pulsed laser deposition (PLD). Their optical constants were then used to design a six layer coating which has less than 2% reflectivity across the visible range (400–700 nm) even at moderate incidence angles. Furthermore, this six layer coating displays large and constant absorbance across the visible range making it optically black. This optical behavior is due largely to the use of the suboxide NbxTi1−xO2 which is unique because of its spectrally constant absorption coefficient.

Design, fabrication, and analysis of double-layer antireflection coatings (ARC) for industrial bifacial n-type crystalline silicon solar cells.

Monocrystalline silicon-based, n-type front and back contact (nFAB) solar cells are gradually attracting more interest from the photovoltaic industry, due to their good bifaciality and high efficiency potentials. To further improve the conversion efficiency, nFAB solar cells need to make better use of the solar spectrum. Conventional single-layer SiNx antireflection coating (ARC) tends to have a high reflection loss for ultraviolet photons. Thus, in this work, we prepare a double-layer ARC structure made of SiNx/SiOx stack, deposited by the plasma-enhanced chemical vapor deposition method. We investigate the effects of double-layer ARC through simulation and experimental studies by fabricating bifacial nFAB cells. The results show that the implementation of a double-layer ARC helps to greatly reduce front reflection in short wavelength, and thus allow for improvement of the photocurrent by up to 0.3 mA/cm2. As a result, the average cell efficiency of nFAB solar cells increases by absolute ∼0.2%.

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.

Design and realization of antireflection coatings for the visible and the infrared based on mesoporous SiO2 and SiO2-TiO2 hybrid materials.

Five-layer antireflective coating for the visible and the infrared has been successfully fabricated by a solgel route on quartz substrate. The quarter-half-quarter multilayer structure with two buffer layers is optimized by the optical admittance approach. Mesoporous SiO2 film templated by an ethylene oxide-propylene oxide-ethylene oxide triblock copolymer is used as the top layer, and SiO2-TiO2 hybrid films are employed as the other layers. The grazing incidence small-angle x-ray scattering results indicate the ordered mesopores in the low-index SiO2 film, as well as the homogeneity of the SiO2-TiO2 hybrid films. Transmittance spectra are fitted to obtain film thicknesses and refractive indices, providing the main technological parameters for theory designs. A short heat-treatment step followed by a shock cooling process is introduced to suppress crack formation in film stacks. The transmittance of the obtained five-layer antireflective coating exceeds 99% at 500-700nm, and the maximum value in the infrared region is 97.84% at 1100nm. This work is a beneficial attempt to fabricate antireflective coatings with multilayer structure through the soft solgel route.

Design and deposition of single and multilayer antireflection coatings of glass substrate using electron beam deposition

E-beam deposition technique offers many advantages compared to other physical vapour deposition techniques in terms of film uniformity, reproducibility and its optical efficiency. In the present work, design and deposition of both single and multilayer antireflection filter has been performed on optical grade glass substrates. Materials for coating were selected on basis of literature review consisting mainly of oxides and fluorides. Thickness of individual layers was optimized using FilmstarTM software for both single and multilayer antireflection coating. The performance of coatings was characterized using various spectroscopic techniques such as UV–Vis spectrophotometer and Gonio spectrophotometer. The peak transmittance was found to be 96.41% for single layer and 94.09% for multilayer antireflection coatings respectively. The performances for both antireflection coatings are compared and analyzed for best possible results. These filters can be used for applications such as transparent industrial display systems, relay optics in complex optical instruments and can further be customized for solar cell application.

色散效应对钝化硅太阳电池减反射膜系设计的影响

色散效应对钝化硅太阳电池减反射膜系设计的影响

Design of Nano-Porous Multilayer Antireflective Coatings

We present an overview of the design potential of nano-porous anti-reflection coatings (ARCs) and the associated challenges in its fabrication. Genetic algorithm optimization for the most effective ARCs on glass for normal and all incident angles is carried out and an admittance loci-based pictorial is used to visualize their performance. We then describe the advantages of using nano-porous multi-layers vis-à-vis other types of moth-eye type nano-grating films: Principally trading high performance and high cost of fabrication for good performance and lower cost facile synthesis. We describe some of the issues involved in the fabrication of such multi-layer stacks on glass and polymeric substrates and provide suggestions for overcoming these limitations.