Antireflective Films Research Articles

One step coating anti-reflective SiO2 film for silicon solar cells applications by atmospheric pressure plasma jet

By utilizing an atmospheric pressure plasma jet, a one-step deposition of anti-reflective silicon dioxide coating was successfully achieved on solar cover glass. A two-dimensional moving platform was utilized to coat large-area cover glass measuring 300 mm * 300 mm. Remarkably, at an input power of 40 W, the temperature of the cover glass remained as low as 59.4 °C. The impact of different motion patterns on the anti-reflective properties of the film was thoroughly investigated. Upon assembling the solar cells, a notable efficiency enhancement from 24.03% to 24.28% was observed. This method demonstrates promising prospects for repairing anti-reflective films on malfunctioning solar cell modules in photovoltaic power plants.

Low polarization-sensitive ultra-broadband anti-reflection coatings with improved reliability.

Broader spectra, lower reflectivity and higher reliability are the performance requirements for broadband antireflective (BBAR) films. In this work, a BBAR film structure was proposed, which maintains extremely low reflectivity, ultra-wide spectra, low polarization sensitivity and practical reliability. The BBAR film consists of a dense multilayer interference stack on the bottom and a nano-grass-like alumina (NGLA) layer with a gradient low refractive index distribution on the top. The film was deposited by atomic layer deposition, while the NGLA layer was formed by means of a hot water bath on Al2O3 layer. The top NGLA layer has extremely high porosity and ultra-low refractive index, along with extremely fragile structure. To surmount the fragility of NGLA layer, a sub-nano layer of SiO2 was grown by atomic layer deposition to solidify its structure and also to adjust the refractive index with different thicknesses of SiO2. Finally, in the wide wavelength range of 400-1100 nm, the average transmittance of the double-sided coated fused quartz reaches 99.2%. The absorption, light scattering, reliability and polarization characteristics of BBAR films were investigated. An optimized BBAR film with low polarization-sensitivity and improved reliability was realized, which should be potentially promising for application in optical systems.

Infrared anti-reflection film device for electromagnetic interference shielding

Infrared anti-reflection film device for electromagnetic interference shielding

Scratch-resistant antireflective coating for mid-wave infrared band

In the 3–5 μm mid-wave infrared (MWIR) atmospheric transparency window region, infrared detectors are widely applied in spectral imaging, remote sensing and other fields, and their rapid development has put forward higher requirements for infrared optical windows. Common mid-wave infrared optical materials such as germanium and zinc sulfide have poor mechanical properties, causing them difficult to meet various harsh environments. In this paper, a 3-layer film stack is proposed to achieve high transmission and high hardness by radio-frequency reactive magnetron sputtering with the single aluminum target. Two types of AlN/Al2O3/AlN stack with top AlN thicknesses of 50 and 100 nm are studied to realize the best optical and mechanical characteristics. The average transmission increases up to 94.0% for 3–5 μm with the double-side AlN/Al2O3/AlN stacks on the silicon substrate, while the hardness is significantly improved to ∼16.6 GPa for both types. After annealing at 500 °C and 750 °C for 6 h in a vacuum environment, the spectra of the two film stacks move towards the shorter wavelength slightly, and the hardness of both are obviously enhanced. The highest hardness of the film system reaches ∼20.8 GPa, making it far more resistant to sand erosion than ordinary antireflection films. The result shows that this film stack can withstand high temperature and gravel impact tests, meeting the service requirements of the harsh environment of the MWIR optical system.

Highly Effective Index-Matching Antireflective Structures for Polymer Optics

Optical polymers are attractive for lightweight and cost-effective refractive optical components, yet they reflect part of the incident light. Traditional vacuum-deposited antireflective films purely adhere to polymers and suffer from mechanical stresses due to the difference in the thermal expansion coefficients. Alternatively, reflection can be reduced by moth-eye structures; yet, their efficiency strongly depends on their index-matching with the optical substrate, which has not been demonstrated so far. Here, we introduce a new approach to engineering highly effective antireflective structures on the surface of the optical polymer, with an unprecedented ability to reduce the surface reflection from 5 to 0.1%. The structures were produced by high-throughput nanoimprint lithography, and their superior optical performance was achieved due to the precise matching of their index to that of the underlying substrate. We further applied these structures on different polymers and showed that their antireflective effect correlates with index-matching. We demonstrated that these structures could be applied on flat surfaces and curved lenses and produce high surface hydrophobicity. Overall, our work paves the way to an efficient and scalable antireflective solution for polymer optics.

Design and Preparation of Anti-Reflection Nanoarray Structure on the Surface of Space Solar Cell Glass Cover

Space solar cell glass covers require high radiation resistance and wide-spectrum high light transmittance. The existing research on the preparation of thin films or special optical structures on the surface of solar cells rarely involves systematic research and the precise control of the high transmittance structural parameters of specific spectral bands by glass covers. Nanoarray structures were designed and constructed on high-purity quartz glass covers, achieving high anti-reflection within the 350–1100 nm range, the high energy part of the solar spectrum on Mars, regardless of the preparation of antireflective film and its radiation resistance. First, G-Solver software package was used to establish a nanoarray structure model according to the equivalent medium theory, and the effects of structural parameters such as the grating period, grating depth, and duty cycle on the glass cover transmittance were investigated. The results show that when the grating period is 50–200 nm, the transmittance ranges from 97.8% to 99.9%. When the grating period further increases from 300 nm, the lowest point of the transmittance spectrum moves to the longwave direction, and the transmittance from 350 nm to the lowest transmittance point significantly reduces. The optimal grating depth is 500 nm for a 300 nm grating period, the transmittance at 350 nm reaches 88.91%, and the average transmittance is 98.23%. When the period is 300 nm and the depth is 500 nm, the optimal duty cycle is 0.67, the transmittance at 350 nm reaches 96.52%, and the average transmittance is 99.23%. Nanoarray structures were constructed on the glass covers with nanoimprint and plasma etching, then modified with atomic layer deposition (ALD) to adjust their depth and duty cycle. The influence rules of the grating period, depth, and duty cycle on the cover transmittance from the experimental results are basically consistent with those from the simulation calculation. The nanoarray structure increases the average transmittance within 350–1100 nm of the glass cover by an average of 2.02% and the peak transmittance by 2.66%. The research results and experimental methods of this study have application value and promotion prospects for improving the photoelectric conversion efficiency of space solar cells and ground solar cells.

Study on the effect of anti-reflection film on the spectral performance of the spectral splitting covering applied to greenhouse

Study on the effect of anti-reflection film on the spectral performance of the spectral splitting covering applied to greenhouse

“Interface-free” ultrabroadband antireflection film based on nanorod structure with continuous change in refractive index

The bandwidth and laser induced damage threshold (LIDT) are the key factors influencing the performance of broadband antireflection (AR) films in optical systems. In this study, we used glancing angle deposition (GLAD) technology to prepare an “interface free” ultrabroadband AR film with continuously varying refractive index and a nanorod structure. Owing to the changing refractive index from substrate to air, the average residual reflectivity of our AR films in the transmission band of 200–2500 nm of the entire fused quartz substrate is less than 0.55%, which is far superior to the traditional broadband AR film. Further, owing to removal of the interface and nanorod structure, the LIDTs of the ultrabroadband AR film at 1064 and 532 nm are 22.5 and 22.6 J/cm2, respectively. These are approximately 50% and 20% higher than those of the traditional 532 and 1064 nm AR film, respectively, indicating superior laser damage resistance.

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.

Ion‐Charged Dielectric Nanolayers for Enhanced Surface Passivation in High Efficiency Photovoltaic Devices

AbstractThe power conversion efficiency of solar cells is strongly impacted by an unwanted loss of charge carriers occurring at semiconductor surfaces and interfaces. Here the use of ion‐charged oxide nanolayers to enhance the passivation of silicon surfaces via the field effect mechanism is reported. The first report of enhanced passivation from rubidium and cesium ion‐charged oxide nanolayers is provided. The charge state and formation energy of ion‐charged silicon dioxide are calculated from first principles. Ion embedding is demonstrated and exploited to control the interface population of carriers and minimize electron‐hole pair recombination. The passivation quality directly improves with charge concentration, yet excess ions can produce detrimental interface states. An optimal ionic charge concentration of ≈1.5 × 1012 q cm−2 is deduced, and a recombination velocity and current density as low as 2.8 cm s−1 and 7.8 fA cm−2 are achieved at the Si‐SiO2 interface. Maximized charge is shown to provide efficiency improvements as high as 0.7% absolute. This work provides a unique route to enhance passivation without compromising the film synthesis, thus retaining the antireflection and hydrogenation film properties. As such, ion‐charged dielectrics provide complementary paths for surface and interface optimization in future single‐junction and tandem solar cells.

Amplification of near field radiation at surfaces of pure dielectric domain with anti-reflection films and photonic crystal structures

With chemical stability under high temperatures, dielectric materials can be idealized thermal emitters for different energy applications. However, dielectric materials do not support surface waves at near-infrared ranges for longer-distance thermal photon tunneling, which limits their applications in near-field thermal radiation. It is demonstrated in this study that thermal field amplification at near-infrared wavelengths at dielectric surfaces could be achieved through asymmetric Fabry–Perot resonance with anti-reflection coatings or 1D photonic crystal type structures. ⩾100 nm near-infrared thermal photon tunneling can be achieved when these thin film structures are added to the emitter and the collector surfaces. Among these two thin film structures, 1D photonic crystal type periodic structures constructed with the same high refractive index material as the emitter/collector material allow near-field thermal photon tunneling at large parallel wavenumbers. Moreover, the field amplification can be increased by adding more 1D photonic crystal layers to achieve even longer distances near field thermal photon tunneling.

Facile preparation of porous SiO2 antireflection film with high transmittance and hardness via self-templating method for perovskite solar cells

An antireflection (AR) film on the surface of the photovoltaic glass can significantly improve the photoelectric conversion efficiency of solar cells. However, AR films prepared by a facile and low-cost sol-gel method usually exhibit poor mechanical properties, which limits their applications. Herein, hexamethoxy methyl melamine resin (CYMEL 303LF) was employed as a pore-forming agent in the sol and sacrificial template to prepare porous SiO2 film on glass by a facile sol-gel method and subsequent heat treatment. The obtained SiO2 film showed a high solar transmittance increase of 3.24% in the wavelength range of 380–1100 nm and a good hardness of H when the dosage of CYMEL 303LF is 10 wt%, the short circuit current density and photoelectric conversion efficiency of the solar cell are increased respectively by 1.44 mA/cm2 and 1.08%, compared with the substrate, which is better than most SiO2 films in the previous works. With increasing the dosage of CYMEL 303LF from 0% to 12%, the solar transmittance gain was increased at first and then decreased, while the film hardness was decreased straightly. This was probably because that the introduction of CYMEL 303LF can facilitate the formation of more pores in the SiO2 film, leading to a decrease in the refractive index and film adhesion. Therefore, this work can provide a facile method to prepare high-performance SiO2 as AR film for solar cells.

Effect of Laser Conditioning on Surface Modification and Laser Damage Resistance of SiO2 Antireflection Film

SiO2 sol-gel antireflection film coated on fused silica can reduce the reflection loss and improve the transmittance of the optical component, although it is still prone to laser induced damage. Laser conditioning is an effective way to improve the laser induced damage threshold (LIDT) of SiO2 sol-gel antireflection film. In this paper, single-layer SiO2 sol-gel antireflection films pretreated by triple-frequency laser with different parameters are characterized by the macroscopical parameters, such as transmittance, refractive index, and thickness. The law of surface modification and the defect removal mechanism of the SiO2 sol-gel antireflection film by laser conditioning are obtained. It is found that laser conditioning can reduce the thickness of the film and introduce densification. In addition, laser conditioning can eliminate micro-defects, such as vacancies and voids in the preparation of SiO2 sol-gel antireflection films, which is the main reason to improve the laser damage resistance of films. Finally, the laser conditioning process with three step laser energy combinations of (0.2–0.6–1.0) Fth0 (zero damage threshold) is the best one to obtain high transmittance, and excellent effects on structure modification and defect removal of films. The research in this paper provides data support for the engineering application and mechanism research of laser conditioning.

Solution-Processed Large-Area Organic/Inorganic Hybrid Antireflective Films for Perovskite Solar Cell.

In recent years, organic/inorganic hybrid materials have attracted much attention in the field of multilayer antireflection films because of their excellent optical properties. In this paper, the organic/inorganic nanocomposite was prepared from polyvinyl alcohol (PVA) and titanium (IV) isopropoxide (TTIP). The hybrid material has a wide, tunable window of refractive index, i.e., 1.65-1.95, at a wavelength of 550 nm. The atomic force microscope (AFM) results of the hybrid films show the lowest root-mean-square surface roughness of 2.7 Å and a low haze of 0.23%, indicating that the films have good potential for optical applications. The double-sided antireflection films (10 × 10 cm2) with one side of hybrid nanocomposite/cellulose acetate and the other side of hybrid nanocomposite /polymethyl methacrylate (PMMA) achieved high transmittances of 98% and 99.3%, respectively. After 240 days of aging testing, the hybrid solution and the antireflective film remained stable with almost no attenuation. Furthermore, the application of the antireflection films in perovskite solar cell modules increased the power conversion efficiency from 16.57% to 17.25%.

Anti-reflective and high-transmittance optical films based on nanoporous silicon dioxide fabricated from templated synthesis

Herein, we report anti-reflective and high-transmittance optical films based on nanoporous silicon dioxide (SiO2) fabricated from templated synthesis. Amorphous mesoporous polystyrene (PS) thin-film templates were prepared by solvent nano-crystallization induced phase separation technique. The mesoporous PS films were used as templates for the preparation of nanoporous SiO2 thin films through the sol-gel method followed by the removal of the template at high temperatures. The nanoporous SiO2 thin films were well-characterized by Field-Emission Scanning Electron Microscopy (FE-SEM), and N2 sorption isotherms for framework size, morphology, surface area, and pore volume respectively. The average pore size for disordered nanoporous SiO2 and calculated porosities are 23 nm and 0.60 respectively. The amorphous nanoporous SiO2 was evaluated for optical reflectance and transmittance in the visible light spectrum and found to have reflectance as low as 6.9% and transmittance as high as 96.5%.

Highly Efficient Perovskite Solar Cells with Light Management of Surface Antireflection

Abstract Perovskite solar cells (PSCs) captivate tremendous interest thanks to high-efficiency and low-cost. Nevertheless, the planar PSCs are negatively affected by serious reflection loss usually because of the refractive index mismatch between the glass substrate and the air, which limits their light harvesting performance. Here, we report an investigation for highly efficient PSCs with light management by applying a structural antireflective film made of polydimethylsiloxane (PDMS) pyramidal texture. Machine learning is firstly used to predict planar (FAPbI3)0.95(MAPbBr2.2Cl0.8)0.05 PSC’ performance for an experimental guide. The experimental results show excellent agreement between the two. When the antireflective film is utilized in the present planar PSCs, an impressive light absorption enhancement is achieved, resulting in a significantly increased power conversion efficiency of up to 23.5%.

Fabrication parameters of spin coating hollow SiO2 nanospheres for antireflection films

Fabrication parameters of antireflection films made of spin coating hollow SiO2 nanospheres were investigated. The film thickness, film morphology and optical properties of the antireflection films were observed dependent on speed of spin coating. With a proper coating speed to produce film of desirable thickness, the antireflection film shows transmittance of 98.7% at λ = 550 nm. We applied a two-step coating to serve as an alternative way for fabrication of hollow SiO2 nanospheres antireflection films. For the antireflection films made by the two-step coating, a relatively improved uniformity in surface morphology and decrease in diffuse reflectance were found. The results suggest using the two-step coating method can be beneficial for uniformity in film morphology and optical properties of the antireflection films.

Research on realizing high permeability and laser stealth compatibility in visible light band with dielectric/metal/dielectric film system

The “cat’s eye effect” in the optical window of all kinds of photoelectric equipment is the main basis of a laser active detection system, which poses a great threat to military equipment and combatants. However, under the condition of ensuring high visible transmittance, the sniper stealth scheme for anti-laser active detection remains to be discussed. In this paper, genetic algorithm is used to inverse design the metasurface anti-reflection film. The three-layer anti-reflection film are composed of Si<sub>3</sub>N<sub>4</sub> and Ag , and rectangular array of metal micro-nano structures is added on the top layer to form a wavelength selective absorber, so as to achieve the effect of low reflection and high absorption at laser wavelength. By combining the device design with genetic algorithm, the parameter combination that best possesses the target performance of the device is obtained. The average transmittance in a wavelength range of 380–780 nm is 88%, and a maximum transmittance peak is 94%. The reflectance and the absorption rate at 1550 nm are achieved to be 10% and 80%, respectively. In order to better meet the requirements for practical application, we further design the cross metal array to obtain polarization insensitive characteristics. The metasurface anti-reflective membrane with improved structure can achieve an average visible transmittance of 82% and a reflectance of 5% at 1550 nm. The two metasurface anti-reflection films designed in this work do not require additional devices, and the imaging quality can be guaranteed. At the same time, it can effectively reduce the laser echo energy, so as to achieve the effect of high-quality visible light transmittance and laser stealth compatibility.

Preparation and Properties of Sol-Gel ZrO2/SiO2 Broadband Antireflective Film

Preparation and Properties of Sol-Gel ZrO2/SiO2 Broadband Antireflective Film

Design and Fabrication of Antireflective Film for Weak Ripple Superluminescent Diode

Design and Fabrication of Antireflective Film for Weak Ripple Superluminescent Diode