Single-layer Antireflection Coatings Research Articles

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.

Numerical Modelling of High Efficiency Silicon Solar Cell Using Various Anti Reflective Coatings (ARC)

The growing prevalence of solar in recent years, which is applied in practically every daily item comprehensively and broadly to make it simpler on consumers due to the consumption of solar resulting in a lot of savings. Anti-reflective coating (ARC) is one of the most important factors contributing to the extensive application of solar. It was acknowledged that ARC had been applied on solar cells to minimize reflection loss, enhance absorption, and boost power conversion efficiency (PCE). The efficiency of solar cell varies depending on the type of ARC material used and its specific characteristics. Since each anti-reflective coating originates from its own formula, there are many different materials produced and manufactured to be applied on solar cells. Hence, in this paper, the simulation of 6 different materials of anti-reflective coating (ARC) coatings has been analyzed and investigated using PC1D simulation software. The outcomes revealed that the ideal wavelength for developing and constructing an ARC would be around 500 and 800 nm. Silicon nitrite (Si3N4) would be the best ARC for designing a single-layer ARC due to its highest efficiency of 21.69 % and exhibits the lowest reflectance, closely followed by zinc oxide (ZnO) which has the efficiency of 21.67 %. Then, zinc sulphate (ZnS) and Titanium Oxide (TiO2) has the efficiency of 21.16 and 21.05 % respectively. While, the silicon dioxide (SiO2) has an efficiency of 20.23 % and lastly, silicon carbide (SiC) has lowest efficiency of 17.07 %. Based on the PC1D simulation software carried out in this research, the data and outcomes regarding the voltage, current, maximum power output, solar efficiency, fill factor, reflectivity, and external quantum efficiency are also reported. HIGHLIGHTS The ARC material and its properties affect solar cell efficiency This study used PC1D simulation software to evaluate 6 anti-reflective coating (ARC) materials The results showed that 500 - 800 nm is the best wavelength for ARC development and construction Silicon nitrite (Si3N4) ARC has the highest efficiency (21.69 %) and lowest reflectance, making it ideal for single-layer ARCs GRAPHICAL ABSTRACT

Experimental and theoretical studies on improving the efficiency of ZnO-based dye-sensitized solar cells using single-layer anti-reflective coating

The effect of a single-layer anti-reflective coating (ARC) on ZnO-based dye-sensitized solar cells (DSSCs) is theoretically predicted and verified by experimental fabrication. By the transfer matrix method (TMM), the absorption of the DSSC with and without the single-layer ARC is calculated and the improvement in short-circuit current density (∆ Jsc%) is estimated. The optimized thickness of the ARC required to obtain maximum improvement in the short-circuit current density (∆ Jsc%) is determined. By employing ARC with the calculated optimized thickness, the fabrication of spin-coated ZnO-based DSSCs is carried out. The structural and optical parameters are studied using XRD analysis and UV absorption spectra. The efficiency of the DSSC with and without the ARC is measured by intensity-modulated photocurrent and photovoltage spectroscopy. The theoretically predicted efficiency of the DSSC with and without ARC agrees well with the experimental values that provide insights about improving the electrical performance of the DSSC by the ARC.

Comparative Study of Polarization‐Dependent Conversion Efficiency of GaAs and Si Solar Cells at Oblique Incident Angles Using Surface DLAR Coating of MgF2/ZnSe

AbstractThe aim of this work is to minimize reflection losses in order to increase the efficiency of solar cells by using anti‐reflection coatings (ARCs). Despite extensive research on improving solar cell conversion efficiency at normal incidence, development at angle of incidence has received little attention. Thus, the reflectivity of single‐layer ARC (SLARC) MgF2 and ZnSe, double‐layer ARC (DLARC), MgF2/ZnSe on Si, and GaAs substrates at transverse electric (TE) and transverse magnetic (TM) modes of polarization in the visible and near‐IR regions for different angles of incidence is analyzed. The optical and electrical properties of Si and GaAs solar cells are analyzed by using the reflectance spectra of SLARC and DLARC at various angles of incidence for the TM and TE modes of polarization under the solar power spectrum (AM1.5). The achieved results due to the effect of DLARC are compared for Si and GaAs solar cells. From these analyses, it is concluded that MgF2/ZnSe is an appropriate DLARC for the range of wavelengths 400–800 nm at 10°–30° angles of incidence in TM mode for tuning the optical and electrical properties of Si and GaAs substrates for terrestrial applications.

Hydrophobic anti-reflective silica hybrid film with tunable refractive index

As one of the important optical films, the anti-reflection film can effectively reduce light reflection at the optical interface, and has wide application potentials in the fields of solar power generation, high-power laser systems, optical devices. However, besides high transmittance, strong environmental resistance and mechanical properties are also needed for anti-reflection coatings in practical applications. In this paper, a series of single-layer hydrophobic anti-reflection silica coatings with adjustable refractive index between 1.13 and 1.44 is obtained via the hybridization of hydrophobic-modified alkali-catalyzed silica hollow nanospheres with hydrophobic acid-catalyzed silica in different proportions, and then used for the construction of double-layer membranes where the top layer has a refractive index of 1.19 and the bottom layer has a refractive index of 1.25. The single-layer film can exhibit nearly perfect transmittance up to 99.2 %, and meanwhile, the double-layer film exhibits excellent broadband anti-reflection with an average transmittance of 98.7 % in the wavelength range from 300 to 900 nm. The hydrophobicity of these films is excellent, and the maximum water contact angle reaches 142°, so the dust pollution hardly leads to the decline of its optical performance. Moreover, the addition of acid-catalyzed sol improves the mechanical properties of the hybrid film while maintaining good transmittance even after the rubbing test.

Numerical analysis of MgF2/SiO2 bilayers anti-reflective coating of light trapping in silicon solar cells by ray tracer software

Anti-reflective coating (ARC) application is continuously being developed extensively and widely for the manufacture of coatings on the surfaces of optical devices which are hugely essential, desirable, and required, particularly on silicon solar cells. Single layer ARC is sufficient, but double layer ARC tremendously enhances solar cell efficiency by covering a wider range of the solar spectrum. Magnesium fluoride, MgF2 and silicon dioxide, SiO2 are the ARC coatings used in this work, with wavelengths in the range from 300 to 1200 nm. The optical properties of bilayer ARC coatings were obtained by varying the thickness of the double coatings and see how the ARC effects Si solar cells. Wafer ray tracer was used in PV Lighthouse software to simulate and model MgF2 and SiO2 bilayer ARC coatings in order to fully understand the performance and impacts of the coatings on Si solar cells. This simulation work contains the analysis of reflection, absorption, transmission, and Jmax, which have been compared to many other theoretical results gathered from other studies and researches. To conclude, the absorption of the wavelength is highest between 500 nm to 900 nm leads to lowest reflection. The output shows that bilayer anti-reflective coatings with the thickness of 75 nm MgF2 and SiO2 are much more effective where the value of Jmax is reach 32.80 mA/cm2. The Jmax enhancement compare to reference is 27.13% is achieved.

Porous but Mechanically Robust All-Inorganic Antireflective Coatings Synthesized using Polymers of Intrinsic Microporosity.

Here, we introduce polymer of intrinsic microporosity 1 (PIM-1) to design single-layer and multilayered all-inorganic antireflective coatings (ARCs) with excellent mechanical properties. Using PIM-1 as a template in sequential infiltration synthesis (SIS), we can fabricate highly uniform, mechanically stable conformal coatings of AlOx with porosities of ∼50% and a refractive index of 1.41 compared to 1.76 for nonporous AlOx that is perfectly suited for substrates commonly used in high-end optical systems or touch screens (e.g., sapphire, conductive glass, bendable glass, etc.). We show that such films can be used as a single-layer ARC capable of reduction of the Fresnel reflections of sapphire to as low as 0.1% at 500 nm being deposited only on one side of the substrate. We also demonstrate that deposition of the second layer with higher porosity using block copolymers enables the design of graded-index double-layered coatings. AlOx structures with just two layers and a total thickness of less than 200 nm are capable of reduction of Fresnel reflections under normal illumination to below 0.5% in a broad spectral range with 0.1% reflection at 700 nm. Additionally, and most importantly, we show that highly porous single-layer and graded-index double-layered ARCs are characterized by high hardness and scratch resistivity. The hardness and the maximum reached load were 7.5 GPa and 13 mN with a scratch depth of about 130 nm, respectively, that is very promising for the structures consisting of two porous AlOx layers with 50% and 85% porosities, correspondingly. Such mechanical properties of coatings can also allow their application as protective layers for other optical coatings.

Utilization of CaF2/ITO Double‐Layer Anti‐Reflective Coating for Increasing the Efficiency in Rear Emitter SHJ Solar Cells

AbstractA method to minimize optical losses in the front side of rear emitter silicon heterojunction (SHJ) solar cells by applying double‐layer antireflection coating (DLARC) has been examined. The primary aim is to increase the short circuit current density (Jsc) using DLARC that is associated with the cell's absorbance. The optical and electrical properties of single‐layer antireflection coating (SLARC) are studied and compared with calcium fluoride (CaF2)/Indium tin oxide (ITO) DLARC.OPAL 2 is utilized as a simulation tool to increase the optical properties of CaF2/ITO DLARC, and the experimental result verifies its validity. ITO is deposited using sputter system while thermal evaporator is utilized to deposit CaF2 to make DLARC. The SHJ solar cell having DLARC demonstrates the average reflection of 6.55% which is 31.7% less than SLARC, that is 9.59% for the wavelength range of 300 to 1100 nm. The fabricated textured solar cell with CaF2/ITO DLARC shows enhancement in external quantum efficiency from 76.89% to 81.06%. It also indicates an improvement in Jsc to 40.83 mA cm‐2 from 39.91 mA cm–2 and having a conversion efficiency of >21% when compared with that of ITO SLARC.

Design and Simulation of Triple Layer Antireflection Coating for Silicon Solar Cells

In present work an attempt has been made to investigate the effect of triple layer anti-reflection coating (TLARC) on the surface of silicon cell theoretically. In this regard, MgF2, Si3N4, and TiO2 have been used to design anti-reflection coatings (ARC). Reflection spectra for single double and triple layer ARCs have been evaluated numerically using transfer matrix method (TMM). Numerically calculated reflection spectra for single, double, and triple layer anti-reflection coatings further used in PC1D simulator to study the performance of silicon solar cell. Result shows reduction in reflectance of silicon solar cell down to less than 3% in the wavelength range 400 – 1200 nm with conversion efficiency 21.6% for TLARC (MgF2/Si3N4/TiO2).

Water-based silica coatings: An environmentally friendly process on an industrial scale of single-layer anti-reflective coatings for large substrates

A new water-based silica sol was developed to provide single-layer anti-reflective (AR) coatings. The combination of nanoparticle-based aqueous coating and wiping-coating method facilitated to reduce the solvent waste. The wiping-coating process requires only 35 ml sol to cover a large glass substrate (80 × 160 cm). Samples coated on one side show an improvement in light transmission in the visible range: the maximum transmission is 95.12 ± 0.33% on float glass and 92.48 ± 0.25% on display glass. This is an excellent performance compared to the extra 99.04% maximum transmission of samples coated on both sides. The layer thickness distribution defined by the ellipsometry of 98 samples (10 × 10 cm) shows homogeneity (77.4 ± 2.2 nm) over the total area. Homogeneous films with good surface wetting were applied on glass, polycarbonate (PC), and acrylic glass (PMMA). The cured layers were successfully tested against dry heat, damp heat (40 °C/98% RH), and climatic change (−40 °C–40 °C/98% RH) on all three substrate materials. No delamination from the substrate was observed. The changes in the minimum reflection after exposure to damp heat and climatic change were minimal (ΔR = ±0.6%) in the wavelength range of 400–1000 nm. The addition of Levasil nanoparticles into the water-based silica sol improved coating hardness on glass sheets up to 3H pencil hardness without significant loss in transmission.

Optimization of Antireflection Coating Design Using PC1D Simulation for c − Si Solar Cell Application

Minimizing the photon losses by depositing an anti-reflection layer can increase the conversion efficiency of the solar cells. In this paper, the impact of anti-reflection coating (ARC) for enhancing the efficiency of silicon solar cells is presented. Initially, the refractive indices and reflectance of various ARC materials were computed numerically using the OPAL2 calculator. After which, the reflectance of SiO2,TiO2,SiNx with different refractive indices (n) were used for analyzing the performance of a silicon solar cells coated with these materials using PC1D simulator. SiNx and TiO2 as single-layer anti-reflection coating (SLARC) yielded a short circuit current density (Jsc) of 38.4 mA/cm2 and 38.09mA/cm2 respectively. Highest efficiency of 20.7% was obtained for the SiNx ARC layer with n=2.15. With Double-layer anti-reflection coating (DLARC), the Jsc improved by ∼0.5 mA/cm2 for SiO2/SiNx layer and hence the efficiency by 0.3%. Blue loss reduces significantly for the DLARC compared with SLARC and hence increase in Jsc by 1 mA/cm2 is observed. The Jsc values obtained is in good agreement with the reflectance values of the ARC layers. The solar cell with DLARC obtained from the study showed that improved conversion efficiency of 21.1% is obtained. Finally, it is essential to understand that the key parameters identified in this simulation study concerning the DLARC fabrication will make experimental validation faster and cheaper.

Optical Characteristics of Antireflection Coatings Based on Al2O3–SiO2 for Silicon Solar Cells

The results from modeling, manufacture, and investigation of the integral reflection coefficient (RS) of single-layer composite antireflection coatings of Al2O3–SiO2 for silicon solar cells with integral reflection coefficient RS ≤ 10% are presented. It was shown that for Al2O3 concentrations of 52–84 wt.%, SiO2 concentrations of 16–48 wt.%, and thickness of 53–97 nm the smallest values of RS are 73–77% for Al2O3 and 27–23% for SiO2 with thickness of 69–75 nm. It was shown experimentally that for layers with Al2O3:SiO2 = 75:25 wt.% with thickness of 72 nm RS = 3.53%, which is approximately half of the RS value for Si3N4.

An environmentally friendly approach to produce single-layer anti-reflective coatings on large surfaces using wet chemical method

Sustainable production of anti-reflective coatings demands environmentally friendly approaches. This paper introduces a novel method of preparing thin films from an aqueous medium using a sol-gel technique. Single-layer anti-reflective coatings, from water-based silica sols, were prepared and characterized. The thicknesses of thin films were found to be between 75 and 135 nm with refractive indexes between 1.23 and 1.41 and porosities between 7 and 53%. The maximum transmissions of manufactured coatings reached from 99.85% to 99.03% in the visible region. The ageing of silica particles in the aqueous medium was studied using TEM. The transparent water-based sol consisted of individual silicon-dioxide nanoparticles with narrow size distribution (15–20 nm). The TEM images showed, that the silica nanoparticles become uniform and distinguishable within two weeks and no aggregation occurs within 46 days. It was found, that the aqueous silica sol is stable and clear for more than 6 months. The aqueous silica films deposited onto large glass surfaces were found to be homogeneous, with excellent adhesion (Cross Hatch Test is 0; ISO 2409 test standard) and hardness equal to 2H. We present a schematic illustration of the adsorption mechanism of non-ionic silicone surfactant and Pluronic surfactant on the silica surface.

Modeling and Analysis of Organic Light Emitting Diode with Thin Film Anti-Reflective Coatings

The effects of anti-reflective coatings (ARC) on organic light emitting diode (OLED) optical characteristics are reported in this paper. The light output produced from the OLED is not 100%. But the emitted light is trapped due to various Modes. The losses at the glass air substrate interfaces of an OLED are addressed in this work. The Anti-Reflective coatings increase the light output by reducing OLED reflections at the interface between glass and air. The Finite Difference Time Domain (FDTD) method and the Fresnel theory have been used to design the device and study the effects on OLED of the Single Layer Anti-Reflective Coating (SLAR) and Double Layer Anti-Reflective Coating (DLAR). The thicknesses and refractive indices of the layers of the anti-reflective coatings were optimized. We also compared the light out coupling power efficiency of the SLAR coated OLED with that of an OLED with a DLAR coating and also with Conventional OLED. The results show that the enhancement in light output efficiency of the DLAR coated OLED was slightly higher than that of the SLAR coated OLED.

Fabrication of mesoporous double-layer antireflection coatings with near-neutral color and application in crystalline silicon solar modules

Single-layer antireflection (SLAR) coatings have been applied in crystalline silicon solar modules for a decade, which evolved from open-pore silica at an early stage into closed-pore structures nowadays in industry. For improving photovoltaic and aesthetic characteristics of solar modules, not only AR properties but also color neutrality of AR coatings need to be intensively studied. In this work, the double-layer antireflection (DLAR) coatings were designed and their residual color was studied by comparing with conventional SLAR and DLAR coatings under both normal and oblique incidences. According to the design, we fabricated the mesoporous DLAR coatings, which exhibited a high average transmittance of Tave = 99.02% at visible wavelengths from 380 nm to 780 nm and a low chroma value of C = 3.35. Applying the mesoporous DLAR coatings to the crystalline silicon mini-modules, the power conversion efficiency was increased by 2.40% on average in relative terms. Besides the power output gain, durable DLAR coatings with neutral color are of great significance for not only imparting a natural and sheer-black appearance to photovoltaic modules without unwanted blueish color, but also finding practical applications in consumer electronics, building glazing, and display windows.

Light scattering characterization of single-layer nanoporous SiO2 antireflection coating in visible light.

Antireflective coatings are widely applied on transparent optical components to reduce reflections at surfaces. Nanoporous silica (NP SiO2) thin films with tailored refractive index properties are used as single-layer antireflective coatings providing nearly zero reflectivity. In this work, light scattering properties of nanoporous silica single-layer antireflective coatings are investigated in order to determine their optical quality by means of total scattering and detailed roughness analysis. Scattering and roughness characterization of the samples coated with different film thicknesses were realized to distinguish the influences of nanopores and surface roughness on scattering losses in the visible (VIS) spectral range. No significant correlation of scattering losses with the film thickness is found, showing negligible influence of the nanopores to the overall scattering properties compared with the dominating effect of interface roughness. Moreover, the scattering losses from coated fused silica glass were observed as low as 20 ppm (0.002%). It is confirmed that NP SiO2 single-layer antireflective coatings are suitable to be used in optics demanding extremely low scattering characteristics.

GaSe crystals with antireflection coatings for terahertz generation

Single- (SiO2) and double-layer (SiO2/Si3N4) antireflection coatings for wavelength region around 800 nm were deposited by magnetron sputtering onto GaSe crystals. The fabricated AR-coated crystals were used for terahertz generation by optical rectification of femtosecond laser pulses. The increase of generated terahertz power by about 28% for the GaSe crystals with the single-layer antireflection coatings was found as consequence of 27 percent increase in transmission through the front face of the crystal.

Optimization of anti-reflective coatings using a graded index based on silicon oxynitride

The present work deals with a comparative study of three anti-reflective coatings (ARCs) based on oxynitride using a gradient refractive index (graded index) following three proposed profiles such as the linear, sub-linear and super-linear profiles. This comparison is based on the quality of the obtained photocurrent density improvement and the normalized photocurrent. At the same time, the conventional single-layer ARC SiO3 and Si3O4 are presented as reference in this comparison. Two parameters are taken into account as the main variables which have the main impact and a degree of sensitivity to the quality of the ARC, the thickness of the layer and the irradiation incidence angle. This study has led to the determination that the super-linear profile is the optimal profile, and that it can be used in multilayer ARCs to ensure optimal energy conversion versus the layers’ thickness and reduced light loss under oblique incidence with improved efficiency.

Model for Characterization and Optimization of Spectrally Selective Structures to Reduce the Operating Temperature and Improve the Energy Yield of Photovoltaic Modules

Many existing commercially manufactured photovoltaic modules include a cover layer of glass, commonly coated with a single layer antireflection coating (ARC) to reduce reflection losses. As many common photovoltaic cells, including c-Si, CdTe, and CIGS, decrease in efficiency with increasing temperature, a more effective coating would increase reflection of sub-bandgap light while still acting as an antireflection coating for higher energy photons. The sub-bandgap reflection would reduce parasitic sub-bandgap absorption and therefore reduce operating temperature. This reduction under realistic outdoor conditions would lead to an increase in annual energy yield of a photovoltaic module beyond what is achieved by a single layer ARC. However, calculating the actual increase in energy yield provided by this approach is difficult without using time-consuming simulation. Here, we present a time-independent matrix model which can quickly determine the percentage change in annual energy yield of a module with a s...

Determination of Refractive Index and Thickness of Nanosized Amorphous Carbon Films Via Visible Range Reflectance Spectra

The values of thickness and refractive index (1.92 < nf < 2.19) of amorphous nanosized carbon films obtained on a crystalline silicon substrate by a pulsed laser deposition were experimentally determined via an analysis of visible range of reflection spectra. Manufactured films can be used as single-layer anti-reflective coatings for Si and GaAs semiconductors.