Double-layer Antireflection Research Articles

Nano-Silica-Based Double-Layer Antireflective Coatings with Mildew Resistance and Moisture Resistance for KDP Crystals.

Sol-gel nano-silica antireflective (AR) coatings with moisture resistance are widely used for optical elements, such as potassium dihydrogen phosphate (KDP) crystals, but their mildew resistance is often disregarded. This work reports a double-layer AR coating with moisture resistance and mildew resistance for KDP crystals. A polydimethylsiloxane-modified dense silica coating and a quaternary ammonium salt (QAS) modified nanoporous silica coating are selected as the bottom layer and top layer, which effectively serve as a moisture barrier and an antireflection layer, respectively. The coated KDP crystal shows excellent antireflection properties with a maximum transmittance of 99.1% at 532nm. Perfluorooctyltriethoxysilane vapor treatment is performed further to improve the resistance to moisture and mildew. The resultant double-layer coating exhibits superior moisture resistance with almost no change in optical transmittance after a 3-month exposure to a high-humidity environment. The introduction of QAS and hydrophobicity in the top layer provides exceptional resistance against mildew, achieving an antimicrobial rate of 99.9% against E. coli and A. flavus. Moreover, the laser-induced damage threshold reaches 17.0 J cm-2 (355nm, 4.5ns). This work imparts moisture resistance and mildew resistance to AR coatings, providing valuable insights for designing multifunctional AR coatings on optical components.

High wear resistant double-layer antireflection coatings for near-infrared vehicular lidar

High wear resistant double-layer antireflection coatings for near-infrared vehicular lidar

Efficiency enhancement of ultrathin CIGS solar cells by optimal bandgap grading. Part II: finite-difference algorithm and double-layer antireflection coatings.

In Part I [Appl. Opt.58, 6067 (2019)APOPAI003-693510.1364/AO.58.006067], we used a coupled optoelectronic model to optimize a thin-film C u I n 1-ξ G a ξ S e 2 (CIGS) solar cell with a graded-bandgap photon-absorbing layer and a periodically corrugated backreflector. The increase in efficiency due to the periodic corrugation was found to be tiny and that, too, only for very thin CIGS layers. Also, it was predicted that linear bandgap-grading enhances the efficiency of the CIGS solar cells. However, a significant improvement in solar cell efficiency was found using a nonlinearly (sinusoidally) graded-bandgap CIGS photon-absorbing layer. The optoelectronic model comprised two submodels: optical and electrical. The electrical submodel applied the hybridizable discontinuous Galerkin (HDG) scheme directly to equations for the drift and diffusion of charge carriers. As our HDG scheme sometimes fails due to negative carrier densities arising during the solution process, we devised a new, to the best of our knowledge, computational scheme using the finite-difference method, which also reduces the overall computational cost of optimization. An unfortunate normalization error in the electrical submodel in Part I came to light. This normalization error did not change the overall conclusions reported in Part I; however, some specifics did change. The new algorithm for the electrical submodel is reported here along with updated numerical results. We re-optimized the solar cells containing a CIGS photon-absorbing layer with either (i)a homogeneous bandgap, (ii)a linearly graded bandgap, or (iii)a nonlinearly graded bandgap. Considering the meager increase in efficiency with the periodic corrugation and additional complexity in the fabrication process, we opted for a flat backreflector. The new algorithm is significantly faster than the previous algorithm. Our new results confirm efficiency enhancement of 84% (resp. 63%) when the thickness of the CIGS layer is 600nm (resp. 2200nm), similarly to Part I. A hundredfold concentration of sunlight can increase the efficiency by an additional 27%. Finally, the currently used 110-nm-thick layer of M g F 2 performs almost as well as optimal single- and double-layer antireflection coatings.

Simple Design of Double-Layer Antireflection Coating for Er-Doped Glass Laser Application

In an Erbium-doped glass laser resonator, parasitic light oscillations (yielding a lowering of the output laser beam power) may be avoided by deposition of well-adapted antireflection coatings on the edges of the active glass medium. However, towards laser application, efficient double-layers are scarce in literature. Here, we propose a simple design of double-layer (total thickness < 490nm) composed of thin films of MgF2 and Al2O3, materials that are easy to deposit by electron beam evaporation. Such coating design allows a calculated reflectance to be lower than 0.01% in the considered 1530-1570nm Near-Infrared range.

Silicon carbide synthesized by RF magnetron sputtering in the composition of a double layer antireflection coating SiC/MgF2

In this paper, the optimal thickness of SiC film for an antireflection coating was determined by computer simulations using Lumerical FTDT and SCOUT software. The simulation was carried out for the SiC/MgF2 system, where silicon carbide films were deposited at a magnetron power of 100, 150, 200, 250 W, while the thickness of the magnesium fluoride films remained unchanged and amounted to 130 nm. The simulation results showed that the optimal parameters for the synthesis of SiC antireflection layer are 100 W/50 nm. With these parameters, the reflection is less than 3% in the widest wavelength range of 475–1020 nm. The dependence of the physical properties of the synthesized films on the power of the magnetron is investigated. Using reflection and transmission spectroscopy it was experimentally revealed that a decrease in the magnetron power from 250 to 100 W leads to a decrease in the refractive index. According to our results the best antireflection effect can be achieved with SiC/MgF2 coatings when SiC films are deposited at 100 W magnetron power. The reflectance spectra are consistent with the simulation spectra, especially in the 475–1020 nm range, where the surface reflects only 0.2–3.0% of the incident light. The obtained results are explained by the correlation between the structural properties, composition of amorphous silicon carbide films and antireflection properties.

Design and development of double-layer anti-reflection coating for HgCdTe based mid-wave infrared detector

A novel design and development of double-layer antireflection coating (ARC) is presented here for back side illuminated HgCdTe based mid- wave infrared (MWIR) detector. Reflectance of infrared radiation in the CdZnTe/HgCdTe structure is simulated to achieve optimum material and thickness of antireflection coating layers for mid- wavelength range. A polishing process for the surface qualification of CdZnTe material prior to deposition of layers has been developed using different chemical treatments and ellipsometric characterisation techniques. The desired ellipsometry parameters (i.e. 4.0<Ψ < 4.6 and 145<Δ<150) of CdZnTe surface is achieved with the polishing of Br2-metanol solution. The optimized ARC layers of YF3 and ZnS are deposited on the back side of CdZnTe surface and measured the reflectance by Fourier-Transform Infrared (FTIR) technique. The reflectance of below 2% is observed in the backside illuminated YF3/ZnS/CdZnTe/HgCdTe structure for mid-wave infrared range, which is similar with the simulated results. Thus, an improvements as well as new functionalities are implemented in infrared sensors by depositing optimum stack of thin film layers.

Influence of Al2O3/IZO double-layer antireflective coating on the front side of rear emitter silicon heterojunction solar cell

Transparent conductive oxide (TCO) thin films play a significant role in silicon heterojunction (SHJ) solar cell and perform both as antireflection coating (ARC) and carrier transport layer. Indium zinc oxide (IZO) films have attracted much attention in opto-electronic industry as an alternative TCO material owing to their superior optical and electrical characteristics as compared to conventionally used indium tin oxide (ITO) films. The optical and electrical properties of IZO films were studied and compared with ITO films. Moreover, the dielectric layer of Al2O3 was deposited on the IZO films using an atomic layer deposition (ALD) system to prepare a double layer antireflection coating (DLARC) structure. The wafer ray tracer simulation tool was used to optimize the thickness of Al2O3/IZO DLARC for SHJ solar cells and experimental results showed its validation. The performance of Al2O3/IZO DLARC on the front surface of rear emitter SHJ solar cell recorded to increase in the current density of 1.37% with enhancement in the efficiency of 0.8%, showing noticeable improvement as compared to cell fabricated with single-layer IZO film.

Selection of Materials for Double Layer Antireflection Coating of Silicon Solar Cell

In present work an attempt has been made to select material to design double layer antireflection coatings (DLARC) for silicon solar cell, theoretically. In this regard, silicon nitride (Si3N4) is used along with MgF2 and SiO2 to design DLARC to achieve zero reflectance over wide range of spectra. Reflection spectra for DLARC systems of MgF2/Si3N4 and SiO2/Si3N4 have been evaluated numerically using transfer matrix method (TMM). Further, reflectance for MgF2/Si3N4 is investigated at various monitoring wavelengths (o = 550, 600, 650 and 700 nm). Calculated reflectance has been used in PC1D simulator to study the effect of double layer antireflection coating on optical and electrical parameters of silicon solar cell. Simulation results shows, reduction in reflectance form &gt; 30% down to zero in the wavelength range 500 – 700 nm with conversion efficiency 21.33% at 600 nm for MgF2/Si3N4.

Full‐Spectrum Absorption Enhancement in a‐Si:H Thin‐Film Solar Cell with a Composite Light‐Trapping Structure

Thin-Film Solar Cells In article number 2000524, Yue Yang and co-workers propose a composite light-trapping structure with a double-layer antireflection coating on the upper surface and Ag hemispheres on the substrate to achieve full-spectrum absorption enhancement in a-Si:H thin-film solar cells. The short-circuit current density and photoelectric conversion efficiency are improved by ∽40% compared to a 100-nm-thick bare cell and increasing the cell thickness to 400 nm could even approach the theoretical absorption limit.

High-low refractive index stacks for broadband antireflection coatings for multijunction solar cells

Antireflection coatings are an interesting challenge for multijunction solar cells due to their broadband spectrum absorption and the requirement of current matching of each subcell. A new design for multijunction solar cell antireflection coatings is presented in this work in which alternative high and low index materials are used to minimize the reflection in a broadband (300–1800 nm). We compared the short circuit current density of high-low refractive index stacks designs with optimum double-layer antireflection coatings by considering two optical materials combinations (MgF2/ZnS and Al2O3/TiO2) for the AM0 and AM1.5D spectra. The calculations demonstrate that for lattice-matched triple-junction solar cells and inverted metamorphic quadruple-junction solar cells, high-low refractive index stacks outperform the optimum double-layer antireflection coatings. The new design philosophy requires no new optical materials because only two materials are used and exhibits excellent performance in broadband spectra. The angle performance of these antireflection coatings is slightly better than classical double-layers whereas the analysis for thickness sensitivity shows that small deviations from deposition targets only slightly impact the performance of antireflection coatings. Finally, some technical solutions for depositing these high-low refractive index multilayers are discussed.

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.

On the origin of spectrally selective high solar absorptance of TiB2-based tandem absorber with double layer antireflection coatings

Despite significant efforts in developing tandem ceramic coatings for photo-thermal conversion applications, the underlying physics behind spectrally selective high absorptance and thermal stability of the ceramic absorbers remains to be addressed. In this perspective, TiB2/Ti(B,N)/SiON/SiO2 and Ti/TiB2/Ti(B,N)/SiON/SiO2 films were developed on stainless steel substrates (SS 304) using pulsed direct current and radio frequency magnetron sputtering. The addition of double layer antireflection coating not only increases the solar absorptance, but also the thermal stability of the tandem absorber. The amorphous coatings exhibit a high solar absorptance of 0.981 at room temperature and an acceptable thermal emissivity of 0.15 at 82 °C. Variable angle spectroscopic ellipsometry analysis reveals a gradient in the refractive indices of the individual layers from the substrate to the top surface. The coatings with and without titanium interlayer were found to be stable for 2 h in air up to 450 °C and 400 °C, respectively. Under vacuum, the coatings exhibited good thermal stability up to 250 h at 500 °C. We make an attempt to explain the high absorptance of the tandem absorber in terms of the composition and gradient in refractive indices across the stack.

Fully screen-printed bifacial large area 22.6% N-type Si solar cell with lightly doped ion-implanted boron emitter and tunnel oxide passivated rear contact

We report on the fabrication of fully screen-printed bifacial large area (239 cm2) high-efficiency n-type Si solar cells with ion-implanted homogeneous boron emitter on the front side and carrier-selective tunnel oxide passivated contact (TOPCon) on the rear. Our phosphorus-doped poly-Si/SiOx passivated contact with SiNx capping layer gave excellent surface passivation with a very low recombination current density (J0_TOPCon) of ~1 fA/cm2 after a simulated firing treatment at ~770 °C without metallization. After screen-printed and fire-through metallization on n-TOPCon with ~13% metal coverage, metallized J0_TOPCon value increased to only ~5 fA/cm2. In addition, homogenous boron implanted emitter (~180 Ω/) passivated with ALD Al2O3 layer capped with PECVD SiNx/SiOx double-layer antireflection (DLAR) coating gave excellent passivation with emitter recombination current density of ~12 fA/cm2 prior to metallization. The industrial screen-printed, fire-through contacts with floating busbars on this boron emitter gave metallized emitter recombination current density of ~31 fA/cm2. This resulted in a low-cost industrial screen-printed n-type bifacial Si solar cell with 22.6% efficiency and 702 mV open-circuit voltage (Voc).

Simulation of multi-layer antireflection film for crystalline silicon solar cell

Based on the design theory of single-layer, double-layer and multi-layer antireflection films, the thickness and refractive index of each layer of three-layer antireflection films are designed and calculated. The theoretical results of double-layer and three-layer antireflection films was simulated by PC1D, and reflectance, internal and external quantum efficiency and device characteristics of solar cells with double-layer and three-layer antireflection coatings were comparative studied. The results show that the three-layer antireflection film has a wider wavelength response range and higher external quantum efficiency, and the conversion efficiency of the three-layer antireflection film Crystalline silicon solar cells is improved by 0.2% compared with the double-layer antireflection film Crystalline silicon solar cells.

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.

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.

Preparation of superhydrophilic silicate coating by sol–gel for double-wavelength broadband antireflective coatings

In the process of realizing double-wavelength broadband antireflection (AR) coatings, it is very important to control the refractive index in a wide range, but at present, many methods of adjusting the refractive index are too complex or expensive. Here, a simple and inexpensive sol–gel route is proposed to prepare the superhydrophilic silica (SiO2) thin films having ultra-low refractive indices by the SiO2 particles surface corrosion with hydrofluoric acid (HF) in sol; this treatment effectively reduces the refractive index of the coating from 1.22 to 1.11. The formation mechanism of the coatings with ultra-low refractive index was discussed in detail. The corrosion of HF on the particles surface significantly improves the hydrophilicity of the coating, and reduces the water contact angle of the coating from 27° to 2°. The bottom layer is prepared by mixing the acid–base complex silica sol. When the refractive indices of the bottom and top layers were set as 1.29 and 1.13, the double-layer double-wavelength AR coating with excellent optical properties has the transmittance of 99.95% and 100.00% at 532 and 1064 nm, respectively.

Effect of obliquity of incident light on the performance of silicon solar cells

The aim of this work is to investigate the effect of angle of incident light on the performance of silicon solar cell. In this regard, numerical calculations have been performed to obtain the reflectance for double layer antireflection coating (DLARC) of Si3N4 at various angles of incidence (i.e.0o,15o,30o,45o,and60o) using transfer matrix method. Reflectances obtained, are found to increases with increase in angle of incidence. Calculated reflectances have been further used in the PC1D simulator as external reflectance files to study the performance of silicon solar cell. As a result of the simulation, the conversion efficiency (and short circuit current) of solar cell is found to decrease by 1.7% (0.062 mA/cm2) with increase in angle of incidence from 0oto60o.

Designing anti-reflection coatings for optical surface

In this paper, we have analyzed the optical properties of single and double layer antireflection coatings with the help of influential characteristics matrix formulation method in the visible electromagnetic spectrum. We have studied deeply for the glass coated with MgF_2 as a single layer coating and the spectrum analysis of double layer coatings of glass with〖 MgF〗_2-Al_2 O_3. With the aid of the algebraic mathematics and MatLab program, we have developed antireflection coating designs which leads to an enhancement of material’s ability for transmission spectrum through it. According to the result we have obtained, it clearly seen that the maximum transmission power for single layer and double layer coatings are about 97.2% which occurs at wavelength of 450 nm and 100% occurs at 324 nm, respectively. It is also observed that the minimum value recorded in transmission spectra for double layer antireflection coating is 99.83% at a wavelength of 418 nm (for normal incidence) and 400 nm (for θ=60° angle of incident). In broadly speaking, our fundamental work shows double layer antireflection coating is more convenient and feasible than single layer antireflection coating.  Â

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%.