Antireflection Research Articles

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

Antireflection microstructures on ZnSe for mid- and far-IR fabricated by femtosecond laser ablation assisted with wet chemical etching

Most infrared materials used in high-power systems, such as optical parametric generators, have high values of refractive indices, which result in high Fresnel losses. The performance of conventional antireflection coatings is limited when used in high-power and ultra-broadband systems. An alternative approach is to fabricate antireflection microstructures (ARMs) that allow for a broadband increase in transmittance without reducing the damage threshold of the material. In this work, ARMs were fabricated on the surface of ZnSe crystals using the femtosecond laser ablation assisted with wet chemical etching method. This allowed to produce high aspect ratio microstructures that increase the transmittance up to 98% in the mid- and far- infrared regions.

Theoretical Analysis and Simulation of SiO2 and ZrO2 Based Antireflective Coatings to Improve Crystalline Silicon Solar Cell Efficiency

The Solar cell efficiency is crucial, and optical losses can hinder it significantly. Anti-reflective coatings are effective in minimizing these losses. In our study, we used Fresnel equations to calculate reflectance values for single-layer SiO2, ZrO2, a SiO2-ZrO2 mixture, and a double-layer SiO2/ZrO2 configuration. We then assessed their impact on crystalline silicon solar cells using the SCAPS program. The reflectance values of single-layer SiO2, ZrO2 and 10%SiO2-90%ZrO2 mixture were calculated as 19.17%, 13.09% and 13.01%, respectively. Notably, the double-layer SiO2/ZrO2 coating showed a low reflectance of 7.58%, a significant improvement compared to uncoated silicon at 37.45%. Efficiency values for crystalline silicon solar cells were calculated for single layer as 18,95% (SiO2), 20.39% (ZrO2), 20,40% (mixed coating) respectively and 21.68% for the double-layer SiO2/ZrO2 configuration.

Easily variable and scalable terahertz pulse source based on tilted-pulse-front pumped semiconductors

A new type of terahertz source containing only two optical elements - a volume phase holographic grating, and a semiconductor nonlinear slab - is proposed. The setup does not require any microstructuring, has only one diffraction order, and can be scaled to large pump sizes without any principal limitations. Furthermore, it can be easily adapted to different pump wavelengths and THz phase-matching frequencies. The Fresnel loss at the boundary of the materials can be significant at conventional pump polarizations (s-pol), but a single-layer anti-reflection (AR) coating can reduce it. Pumping such a setup with polarization in the dispersion plane (p-pol, TM mode) can reduce the effective nonlinear polarization and consequently the terahertz generation efficiency. However, in the absence of AR coating, this reduction is overcompensated by the reduced Fresnel loss.

Evaluation of hydrophobic/hydrophilic and antireflective coatings for photovoltaic panels

Evaluation of hydrophobic/hydrophilic and antireflective coatings for photovoltaic panels

Improvement strategy evaluation from coupled energy-flow perspective on the GaSb thermophotovoltaic cell

Thermophotovoltaic (TPV) emerges as a novel high-efficiency generation technology, showcasing enormous potential in various sustainable energy solutions. Aiming to understand the complex conversion process between radiative, electrical and thermal energies within TPVs, a multi-physics coupled model is established. From the heat generation, temperature and carrier perspectives, the output performance is analyzed in detail. Under 1200 K black-body radiation, the energy loss distribution in the GaSb cell is analyzed meticulously, where Joule heat (40.4 %), surface recombination heat (23.1 %) and thermalization heat (20.8 %) play predominant roles. As it stands, the cell temperature rises to a maximum of 317.0 K with a cooling intensity of 300 W/(m2·K). The minimum of the average cell temperature (approximately 312.3 K) occurs at the optimized working voltage of 0.3 V. Subsequently, the electrical characteristics are illustrated. The results indicate a maximum output power underestimation of 4.6 % compared to the uncoupled isothermal case. Based on the coupled model, a quantitative analysis of the anti-reflection coating (ARC), the structural adjustment (SA) and the selective emitter (SE) is conducted. The results reveal that the ARC case exhibits the most enhancement in the output power (55.3 %) followed by the SA case, which effectively improves it by 12.2 %. Although the SE case partially decreases the output power (−9.8 %), it shows promise in promoting conversion efficiency. Integrating the above strategies, the TPV system achieves an impressive conversion efficiency of 29.38 %, representing a 76.46 % improvement compared to the prototype with the cell only.

Mid-infrared interference coatings with excess optical loss below 10 ppm: erratum

This erratum addresses incorrect labeling of crystal axes in our published results [Optica 8, 686 (2021)OPTIC82334-253610.1364/OPTICA.405938], as well as a mistaken reference in the supplementary document.

Synthesis, characterization, and application of silica aerogel thin films prepared via surface derivatization: A comprehensive study on micro-silica nanofilms for enhanced photoelectric conversion efficiency in photovoltaic solar cells

Silica aerogels are nanoporous materials with exceptional optical and physical properties, making them promising candidates to enhance solar cell efficiency as antireflective coatings. This study synthesized hydrophobic silica aerogel thin films under ambient conditions and characterized their porous structure, surface morphology, and optical performance. The films were deposited on monocrystalline silicon solar cells to assess their impact on photovoltaic properties. A two-step acid/base catalyzed sol-gel process was utilized, followed by solvent exchange and surface modification with trimethylchlorosilane. Structural analysis via SEM revealed successful deposition of crack-free films when aging occurred in an ethanol environment. The aerogel displayed considerable specific surface area (115 m2/g), porosity (77.92%) and surface roughness (55-78%) along with a low refractive index (1.05), benefiting light harvesting. Preliminary solar testing showed increased output voltage with a 0.2 mm aerogel coating versus a bare cell. Further IV measurements demonstrated enhanced charge transport and conversion efficiency for the treated cell. The aerogels antireflective and light-trapping effects appear to improve photon absorption. This initial research validates the potential of ambient pressure-synthesized hydrophobic silica aerogels to increase the performance of silicon photovoltaics cost-effectively. Further optimization of film thickness and morphology could realize higher efficiency gains.

Multifunctional coatings for solar module glass

AbstractCurrently, single‐layer antireflection coated (SLARC) solar glass has a dominant market share of 95% compared to glass with other coatings or no coating, for Si PV modules. This antireflection coating (ARC) results in an efficiency gain of 2–3%. However, there are issues with these SLARCs: (1) solar cell warming due to increased sub‐bandgap light absorption (by +0.4 ~ 1.2 K), counteracting the cell current gain and accelerating the aging of the solar panels, and (2) poor durability due to the coating's porous structure (typically lasting ≤5 years). This paper aims to develop a non‐porous multilayer coating (MLC) that is more durable and will act as a spectrally selective filter for solar modules. Studies have been conducted on MLCs in terms of optical, microstructure, mechanical, and durability properties compared with commercial single‐layer AR coatings. The MLCs showed superior performance in durability and benefit in reducing parasitic heat absorption in the non‐usable wavelength range. Also, a techno‐economic analysis model based on the multifunctional coating specifically to evaluate economic benefits has been developed.

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.

Highly efficient anti-reflection coating on transparent material surface by a deposition-oxidation two-step process using very high-frequency plasma under atmospheric pressure

Using atmospheric-pressure (AP) helium (He)-based plasma excited by a 150 MHz very high-frequency (VHF) power, the formation of low-refractive-index silicon oxide (SiOx) layers for single-layer quarter-wave anti-reflection (AR) coatings of transparent substrate materials is studied. To effectively lower the refractive index of SiOx layers, a deposition-oxidation two-step process is adopted. Specifically, carbon and hydrogen-containing silicon oxide (SiOCH) films are coated in hexamethyldisiloxane and hydrogen-fed plasma on the substrates with fine polystyrene spheres arranged, and subsequently oxidized in oxygen-fed plasma. During the post-oxidation process, the SiOCH film is transformed into silica (SiO2)-like one and the polystyrene spheres underlying the film is simultaneously oxidized to be removed. As a result, a SiO2-like film with a very low refractive index of 1.23 and with excellent adhesion to the substrate is obtained. It is also demonstrated that the low-refractive-index coating functions well as a quarter-wave AR coating of a glass substrate.

First-principles prediction of antimony based XSbF3 (X = Be, Mg, Ca and Sr) fluoroperovskites: An insight into structural, optoelectronic and thermal properties

First-principles computations have been carried out to explore the structural, optoelectronic and thermodynamic characteristics of antimony-based fluoroperovskites XSbF3 (X = Be, Mg, Ca, Sr) compounds. The optimized lattice constants of 4.46, 4.60, 4.72 and 4.81 Å are obtained for BeSbF3, MgSbF3, CaSbF3 and SrSbF3 compounds, respectively. The negative values of the binding energy of these compounds advocate that these compounds are structurally and thermodynamically stable. The electronic properties such as band structures, density of states and partial density of states reveal the metallic character of the studied compounds. Various optical and thermal parameters have been discussed in detail. To the best of our knowledge, this is the first theoretical attempt to study the physical properties of XSbF3 (X = Be, Mg, Ca, Sr) fluoroperovskite compounds. The findings of this study yield useful insights into the potential implementation of these compounds for the development of lenses, anti-reflection coatings and other valuable optoelectronic devices.

Enhancing photovoltaic cell efficiency: A comprehensive study on BN-Si3N4 blend antireflective coatings and their impact on power conversion

Antireflective surface coatings were one of the most important factors that contributed to the improvement of the functionality of photovoltaic cells. The coatings were performed by different methods such as RF sputtering, spin coating, dip coating, electro spraying etc. The coating materials such as BN, Si3N4 and BN-Si3N4 blends were applied to solar cells using the RF sputtering technique in this study. Several distinct characterization methods were adopted to assess the productivity of Si3N4 coated cells. The BN-Si3N4 blend coated cell has a low light reflection of 8 % and exhibits uniform layer deposition, which shows a significant improvement over conventional solar cell. The BN-Si3N4 solar cell was able to obtain the highest possible power conversion efficiency of 19.70 % when exposed to direct sunlight and 21.28 % when exposed to neodymium light. It possess the narrow scope of visible spectrum and acts as green/yellow filter in visible spectrum. This light is capable of delivering light similar to sunlight with consistent radiation. This was accomplished by increasing the transmission of photons that reached the depletion region. The four-probe experiment was employed to measure the electrical resistivity of BN-Si3N4 solar cell, which was found to be 0.00298 Ω-cm. This value was lower than the electrical resistivity of other solar cell samples. Based on the results, BN-Si3N4combination outperformed both coated and bare cells. It was found that BN-Si3N4blendwas a remarkable antireflective coating to maximize the performance.

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

Fabrication of a Porous Low Refractive Index Anti-Reflective Coating with High Transmittance by Using the Porogen of Laureth-5 Carboxylic Acid

A porous anti-reflective coating (P-ARC) with average transmittance in the visible range of 97.9% was fabricated through the sol-gel method, followed by calcination at a relatively low temperature (220 °C) using the porogen of Laureth-5 carboxylic acid via a one-step approach. The results demonstrated the coating had an absolute value that was 7.5% higher than that of bare glass (92%). The prepared porous anti-reflective coating had a refractive index as low as 1.21. The coating remained undamaged during 3M tape stripping tests while maintaining excellent light transmittance. This work presents a film that has good thermal stability, chemical stability, and mechanical stability.

Analytical modeling of acoustic exponential materials and physical mechanism of broadband anti-reflection

Spatially exponential distributions of material properties are ubiquitous in many natural and engineered systems, from the vertical distribution of the atmosphere to acoustic horns and anti-reflective coatings. These media seamlessly interface different impedances, enhancing wave transmission and reducing internal reflections. This work advances traditional transfer matrix theory by integrating analytical solutions for acoustic exponential materials, which possess exponential density and/or bulk modulus, offering a more accurate predictive tool and revealing the physical mechanism of broadband anti-reflection for sound propagation in such non-uniform materials. Leveraging this method, we designed an acoustic dipole array that effectively mimics exponential mass distribution. Through experiments with precisely engineered micro-perforated plates, we demonstrate an ultra-low reflection rate of about 0.86% across a wide frequency range from 420 Hz to 10,000 Hz. Our modified transfer matrix approach underpins the design of exponential materials, and our layering strategy for stacking acoustic dipoles suggests a pathway to more functional gradient acoustic metamaterials.

Mechanically-Durable Antireflective Subwavelength Nanoholes on Glass Surfaces Using Lithography-Free Fabrication.

Traditional multilayer antireflection (AR) surfaces are of significant importance for numerous applications, such as laser optics, camera lenses, and eyeglasses. Recently, technological advances in the fabrication of biomimetic AR surfaces capable of delivering broadband omnidirectional high transparency combined with self-cleaning properties have opened an alternative route toward realization of multifunctional surfaces which would be beneficial for touchscreen displays or solar harvesting devices. However, achieving the desired surface properties often requires sophisticated lithography fabrication methods consisting of multiple steps. In the present work, we show the design and implementation of mechanically robust AR surfaces fabricated by a lithography-free process using thermally dewetted silver as an etching mask. Both-sided nanohole (NH) surfaces exhibit transmittance above 99% in the visible or the near-infrared ranges combined with improved angular response at an angle of incidence of up to θi = 60°. Additionally, the NHs demonstrate excellent mechanical resilience against repeated abrasion with cheesecloth due to favorable redistribution of the shearing mechanical forces, making them a viable option for touchscreen display applications.

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.

Plasma-enhanced atomic-layer-deposited HfO2–SiO2 nanolaminates for broadband antireflection coatings

The ever-increasing demand for broadband antireflection (AR) coatings has led to a growing interest in nanolaminates (NLs) with tunable properties. However, achieving excellent optical performance in NLs can be challenging due to multiple interfaces and a rather thin sublayer. In this study, we systematically investigated the factor that deteriorates the optical performance, focusing on the sublayer thickness deviation, sublayer n deviation, and interfacial diffusion, to correct the n-profiles of NLs. A pre-correction strategy for the AR coating design is proposed and experimentally demonstrated via plasma-enhanced atomic layer deposition. The excellent fit of the spectrum demonstrates that the proposed design strategy can benefit structure-sensitive NL-based coatings.

Performance Comparison of Si and GaAs Solar Cell due to Deposition of ZnO and SiO2 Antireflection Coating Layer

Performance Comparison of Si and GaAs Solar Cell due to Deposition of ZnO and SiO2 Antireflection Coating Layer