Antireflective Surfaces Research Articles

Bioinspired Antireflective and Antifogging Surface for Highly Efficient and Stable Inverted Solar Cells.

Photovoltaic devices are essentially solar energy collectors that convert incident photons into charge carriers. However, light reflection losses and external factors (e.g., fog) can lead to an inefficient utilization of incident photons. Therefore, the development of antifogging surface materials that can efficiently reduce reflection is a critical issue in the upgradation of photovoltaic devices. Herein, inspired by the wing scale structures of butterfly Trogonoptera brookiana, an antireflective and antifogging surface (BRFS) was prepared by a method combining biotemplate and sol-gel. Remarkably, the BRFS possesses a relatively large surface roughness and exhibits superhydrophilic property (static water contact angle of 0°), which can quickly split fog droplet film within 6.6 s to realize the antifogging effect. In addition, the final transmittance of BRFS is as high as 90.25%. Furthermore, as an application demonstration, BRFS was applied to the surface of the reverse organic solar cells. Without compromising the inherent performance of the panels, the BRFS enhances the electrical performance of the inverted solar panels by 18%. This work provides a simple and effective strategy for designing surfaces with superior antifogging and antireflective properties and offers significant potential value for the practical application of photoelectric devices.

Reversible Antireflection Materials Inspired by Cicada Wings for Anticounterfeit and Photovoltaic Cells.

Antireflection (AR) surfaces are essential for the fields of flexible displays, photovoltaic industry, medical endoscope, intelligent windows, etc. Although natural creatures with well-organized micro/nanostructures have provided some coupling design principles for the rapid development of bioinspired AR materials, the mechanical vulnerability, poor flexibility, and nonadjustability have been pointed out as the drawback of these nanostructures. Here, a bioinspired reversible AR film with 4% reflectivity, 90% transmittance, and 9% haze in broadband (400-900 nm) was prepared. The flexible switching of AR performance enhancement and weakening throughout the visible wavelength band has been achieved by controlling the reversible change in the morphology of the interface structure. A variety of patterned film samples can be obtained by simply changing the template, which can be used in intelligent identification fields such as anticounterfeiting. The cycle test and photoelectric test show that the bionic reversible antireflection structure has certain stability and can effectively reduce the loss of photovoltaic cell conversion efficiency caused by mechanical deformation. It has broad application prospects in the fields of anticounterfeiting, intelligent window, flexible display, photoelectric element, and so on.

Hierarchical Micro/Nanostructures with Anti-Reflection and Superhydrophobicity on the Silicon Surface Fabricated by Femtosecond Laser

In this paper, hierarchical micro/nano structures composed of periodic microstructures, laser-induced periodic surface structures (LIPSS), and nanoparticles were fabricated by femtosecond laser processing (LP). A layer of hydrophobic species was formed on the micro/nano structures through perfluorosilane modification (PM). The reflectivity and hydrophobicity’s influence mechanisms of structural height, duty cycle, and size are experimentally elucidated. The average reflectivity of the silicon surface in the visible light band is reduced to 3.0% under the optimal parameters, and the surface exhibits a large contact angle of 172.3 ± 0.8° and a low sliding angle of 4.2 ± 1.4°. Finally, the durability of the anti-reflection and superhydrophobicity is also confirmed. This study deepens our understanding of the principles of anti-reflection and superhydrophobicity and expands the design and preparation methods for self-cleaning and anti-reflective surfaces.

Dual-Coated Antireflective Film for Flexible and Robust Multi-Environmental Optoelectronic Applications.

Artificial antireflective nanostructured surfaces, inspired by moth eyes, effectively reduce optical losses at interfaces, offering significant advantages in enhancing optical performance in various optoelectronic applications, including solar cells, light-emitting diodes, and cameras. However, their limited flexibility and low surface hardness constrain their broader use. In this study, we introduce a universal antireflective film by integrating nanostructures on both sides of a thin polycarbonate film. One side was thinly coated with Al2O3 for its high hardness, enhancing surface durability while maintaining flexibility. The opposite side was coated with SiO2 to optimize antireflective properties, making the film suitable for diverse environments (i.e., air, water, and adhesives). This dual-coating strategy resulted in a mechanically robust and flexible antireflective film with superior optical properties in various conditions. We demonstrated the universal capabilities of our antireflective film via optical simulations and experiments with the fabricated film in different environments.

Correction to: Fabrication of superhydrophobic, permeable, and anti-reflective porous steel surfaces using laser ablation and heat treatment

Correction to: Fabrication of superhydrophobic, permeable, and anti-reflective porous steel surfaces using laser ablation and heat treatment

Light-trapping by wave interference in intermediate-thickness silicon solar cells

The power conversion efficiency of crystalline silicon (c − Si) solar cells have witnessed a 2.1% increase over the last 25 years due to improved carrier transport. Recently, the conversion efficiency of c − Si cell has reached 27.1% but falls well below the Shockley-Queisser limit as well as the statistical ray-optics based 29.43% limit. Further improvement of conversion efficiency requires reconsideration of traditional ray-trapping strategies for sunlight absorption. Wave-interference based light-trapping in photonic crystals (PhC) provides the opportunity to break the ray-optics based 4n 2 limit and offers the possibility of conversion efficiencies beyond 29.43% in c − Si cells. Using finite difference time domain simulations of Maxwell’s equations, we demonstrate photo-current densities above the 4n 2 limit in 50 − 300µm-thick inverted pyramid silicon PhCs, with lattice constant 3.1µm. Our 150µm-thick PhC design yields a maximum achievable photo-current density (MAPD) of 45.22mA/cm 2. We consider anti-reflection coatings and surface passivation consisting of SiO 2 − SiN x − Al 2 O 3 stacks. Our design optimization shows that a 80 − 120 − 150nm stack leads to slightly better solar light trapping in photonic crystal cells with thicknesses <50µm, whereas the 80 − 40 − 20nm stack performs better for cells with thicknesses >100µm. We show that replacing SiN x with SiC may improve the MAPD for PhC cells thinner than 100µm. For a fixed lattice constant of 3.1µm, we find no significant improvement in the solar absorption for 50 and 100µm-thick cells relative to a 15µm cell. A substantial improvement in the MAPD is observed for the 150µm cell, but there is practically no improvement in the solar light absorption beyond 150µm thickness.

Fabrication of superhydrophobic, permeable, and anti-reflective porous steel surfaces using laser ablation and heat treatment

Fabrication of superhydrophobic, permeable, and anti-reflective porous steel surfaces using laser ablation and heat treatment

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.

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.

SCATTERING OF ELECTROMAGNETIC WAVES ON FLAT GRID TWO-PERIODIC STRUCTURES

Context. One of the scientific hypotheses for the creation of nonreciprocal optical metasurfaces is based on the use of a wave channel in which rays of the direct and reverse diffraction scenarios are realized on two-periodic flat structures with nonlinear elements. Such processes in the nanometer wavelength range of electronic devices require precise calculations of the interaction of waves and microstructures of devices. It is also important to describe the behavior of antenna devices in mobile communications. Expanding the wavelength range of stable communication is achieved by using prefractal structures in antenna devices in combination with periodic structuring. Similar modeling problems arise when electromagnetic waves penetrate materials with a crystalline structure (radio transparency).
 Objective. To test this hypothesis, it is necessary to carry out mathematical modeling of the process of scattering of electromagnetic waves by metasurfaces under conditions of excitation of several diffraction orders. It is known that among two-periodic flat lattices of different structures there are five types that fill the plane. These are the Bravais grilles. The problem of scattering of an incident monochromatic TE polarized wave on a metal screen with recesses in two-periodic structures filled with silicon was considered.
 Method. The paper builds mathematical models for the study of spatial-amplitude spectra of metasurfaces on Brave lattices and gives some results of their numerical study. The condition for determining the diffraction orders propagating over the grating is proposed. Scattered field amplitudes are from the solution of the boundary value problem for the Helmholtz equation in the COMSOL Multiphysics 5.4 package. Similar problem formulations are possible when studying the penetration of an electromagnetic field into a crystalline substance.
 Results. Obtained relations for diffraction orders of electromagnetic waves scattered by a diffraction grating. The existence of wavelengths incident on a two-periodic lattice for which there is no reflected wave is shown for different shapes (rectangular, square, hexagonal) of periodic elements in the center of which a depression filled with silicon was made. Distributions of reflection coefficients for different geometric sizes of colored elements and recesses are given. The characteristics of the electric field at resonant modes in the form of modulus isolines show the nature of the interaction of the field over the periodic lattice and the scatterersdepressions. At the resonant wavelengths of the incident waves, standing waves appear in the scatterers.
 Conclusions. A mathematical model of the set of diffraction orders propagating from a square and hexagonal lattice into halfspace is proposed z >= 0. It has been shown that flat periodic lattice with square or hexagonal periodicity elements and resonant scatterers in the form of cylindrical recesses filled with silicon can produce a non-mirrored scattered field in metal. The response of the lattices to changes in the wavelength of the incident field by the structure of diffraction orders of the scattered field and high sensitivity to the rotation of the incident plane were revealed. The two-periodic lattices have prospects for creating anti-reflective surfaces of various devices. Two-periodic lattices have prospects for creating anti-reflective surfaces for various devices, laser or sensor electronic devices, antennas in mobile communication elements, and radio transparency elements. They have more advanced manufacturing technologies in relation to spatial crystal structures.

Photonic Crystal Structures for Photovoltaic Applications.

Photonic crystals are artificial structures with a spatial periodicity of dielectric permittivity on the wavelength scale. This feature results in a spectral region over which no light can propagate within such a material, known as the photonic band gap (PBG). It leads to a unique interaction between light and matter. A photonic crystal can redirect, concentrate, or even trap incident light. Different materials (dielectrics, semiconductors, metals, polymers, etc.) and 1D, 2D, and 3D architectures (layers, inverse opal, woodpile, etc.) of photonic crystals enable great flexibility in designing the optical response of the material. This opens an extensive range of applications, including photovoltaics. Photonic crystals can be used as anti-reflective and light-trapping surfaces, back reflectors, spectrum splitters, absorption enhancers, radiation coolers, or electron transport layers. This paper presents an overview of the developments and trends in designing photonic structures for different photovoltaic applications.

Enhancing anti-reflective properties of electronic glass through two-step chemical etching

With the rapid growth of the electronic display industry, aluminosilicate glass has emerged as a replacement for traditional soda lime silica glass as the cover plate of various display devices because of its excellent physical and chemical properties. High transmittance and low reflectivity are the inevitable requirements of its application. However, few studies have been reported about the antireflection of aluminosilicate glass. In this study, a two-step etching method was employed to treat both sides of the alkali-aluminosilicate glass to obtain surface antireflection. Analytical methods such as EPMA, AFM, and UV spectrophotometry were utilized to evaluate the effect of the etching process and resultant surface microstructure on the optical properties of the glass. Furthermore, comparative research was conducted to distinguish the etching reaction differences between alkali-aluminosilicate glass and other glass compositions like soda-lime glass and high-boron-silicon glass. The results demonstrated that the controlled two-step etching process created a micro-porous surface structure, with a gradient refractive index. Subsequent to the secondary etching, the glass exhibits an impressive average transmittance of 98.88% within the visible light spectrum (380–780 nm). Moreover, identical etchant across different composition glasses leads to discernible differences in transmittance.

Micro nano antireflective and hydrophobic hierarchical structures ZnS by femtosecond laser

Antireflective hydrophobic hierarchical structures were fabricated on ZnS with ultralow reflectance by femtosecond laser. By adjusting the scanning interval, laser scanning speed and laser power, different kinds of hierarchical structures were obtained. The hierarchical structures combined the light trapping effect of micro-structures and effective refractive index medium effect of nano structures, greatly reduced the reflectance. At optimal parameters, the reflectance of ZnS with hierarchical structures decreased to lower than 1.4 % in the wavelength of 500–2500 nm. Besides, the hierarchical structures featured good hydrophobic performance with contact angle of 114°. This work provided a new way for the surface antireflection and hydrophobicity process, which could be widely used in the optical windows, and photoelectron devices.

Nanosecond Laser Fabrication of Novel Micro-/Nanostructured Metal Surfaces: A Dual-Functional Supersurface Combining Antireflectivity and Superhydrophobic Properties.

The research and applications in the field of micro/nano surface manufacturing are progressively shifting their focus toward multifunctional surfaces. In practical applications, objects often need to operate under demanding environmental conditions, and single-function surfaces have inherent limitations in terms of performance, adaptability, and longevity. In this paper, a micro-/nanolayered structural strategy with dual functions of ultrahigh antireflective properties and superhydrophobicity was created on the surface of titanium alloy by using nanosecond pulsed laser processing, and two structural modes of periodic honeycomb and lattice with controllable shapes were designed. In addition, the morphology and formation mechanism of multilevel micro-/nanostructures were investigated in depth, combining laser texturization and silanization of substrate microstructures. The effects of the micro-/nanostructured morphology on the reflection and wettability properties were evaluated with different pulse widths and lateral overlap index. This study also demonstrated that water droplets exhibit excellent bouncing and rolling behavior on superhydrophobic surfaces, further verifying the excellent hydrophobic properties of the prepared samples. Furthermore, in addressing the challenges of susceptibility to dust contamination and performance degradation in extreme environments associated with antireflective surfaces, a series of durability and mechanical stability tests were conducted on controllability periodic micro-/nanostructured surfaces. Successfully meeting this challenge will open up great potential and opportunities for significant improvements in equipment performance and stable operation under extreme operating conditions.

Surface engineering of Sio2-Zro2 films for augmenting power conversion efficiency performance of silicon solar cells

Improving solar cell performance hinges significantly on the application of anti-reflective surface coatings. A wide variety of coating techniques, including blade coating, spin coating, dip coating, and others were employed. The present research investigation employed various coating materials, namely SiO2 (Silicon dioxide), ZrO2 (Zirconium dioxide), and SiO2–ZrO2 blends, to apply a protective layer onto polycrystalline silicon solar cells using the sputter coating process. The efficiency of these solar cells with multilayer coating was assessed through diverse characterization methods. The uniform thin films were obtained using a 45-min coating process using an input voltage source of 17 kV, which was confirmed through analyses conducted using FESEM and AFM techniques. The UV–Vis spectroscopy and current-voltage source metre were employed to examine the light absorption and transmittance of bare and coated silicon solar cells. When compared to alternative solar cells, the solar cell coated with a combination of SiO2 and ZrO2 demonstrated uniform deposition and a low light reflectance of only 6 %. SiO2–ZrO2 gains a highest power conversion efficiency (PCE) of 17.6 % under controlled light source. This superior performance was due to the increase in photon transmittance in to the depletion region. Furthermore, the electrical resistivity of the SiO2–ZrO2 blend coated solar cell was measured using the four-probe method was found to be 2.89 × 10−3 Ω-cm, which was lower than that of other solar cells. From the experimental results, it was clear that SiO2 - ZrO2 blend-coated solar cells outperformed both other coated and uncoated solar cells. Consequently, SiO2–ZrO2 blends emerged as superior anti-reflective materials for achieving peak performance.

Rapid fabrication of antireflective structures on ZnS surface by spatial shaping femtosecond laser

Antireflection performance and fabrication efficiency are key factors that affect the practical application of antireflective structures. Nowadays, how to combine good antireflection performance with highly efficient processing is still a difficult problem. In this work, a novel and scalable method of fabrication of antireflective LIPSS (laser induced periodic surface structure) on ZnS surface by spatial shaping femtosecond laser is proposed. A Gaussian beam is converted to a line beam by a cylindrical lens transformation. The focal long axis of line beam is on the scale of centimeters, and the minor axis is on the scale of micrometers. Hence, the fabrication efficiency can be significantly improved by adjusting the scanning direction perpendicular to the major axis. Notably, the proposed highly efficient method only takes 21 s to complete the fabrication of 1 × 1 cm2 antireflective ZnS surface with excellent antireflective property. At the laser power of 500 mW, scan speed of 1.0 mm/s, scan interval of 0.55 cm, the transmittance of fabricated antireflective structures maintains 78–87.5% at 2.5–10 μm, with the average transmittance of 81.3%, 5.9% higher than that of untreated ZnS. This proposed method may open a revolutionary concept for the rapid antireflective surface laser processing, which has a great application potential in energy, military, aerospace and other fields.

Properties of Black Silicon Layers Fabricated by Different Techniques for Solar Cell Applications

Black silicon (BS) layers coated with passivation films are widely used as antireflective frontal surfaces for solar cells. The most common BS fabrication techniques are reactive ion etching (RIE), metal‐assisted chemical etching, and laser‐induced processing. Herein, the structural and optical properties, as well as the minority carrier lifetime, of BS are compared with and without atomic layer deposited HfO2 passivation films produced by the above formation methods. The antireflection behavior of the samples is discussed based on the light trapping effect and the change in the BS refractive index from air to the bulk of crystalline Si. Finally, test solar cells are manufactured, and their photovoltaic parameters are studied. The comparison results show that RIE is the most preferred in all technical respects. The features of using different BS fabrication techniques from the solar cell manufacturing point of view are analyzed.

Design of a novel anti-reflective coating with ultra-low reflectance based on resin-anchored hollow silica strategy

The strategy of resin-anchored hollow silica particles (HSPs) offers a tempting option for large-scale fabrication of anti-reflective functional surfaces on flexible plastic substrates. However, attempts to experimentally investigate the structure-performance relationship of such anti-reflective coatings and to further optimize the coating structure require long experimental cycles and significant labor costs. In view of this, the effectiveness of using COMSOL two-dimensional (2D) simulation to solve the problem is validated in conjunction with experimental results. Then three coating structure models are investigated. Finally, a coating with ultra-low reflectance in the entire visible wavelength band (380–780 nm) is designed. The coating has a novel structure consisting of resin-anchored double-layer unequal-size HSPs. It combines two anti-reflective principles, the moth-eye bionic structure and the refractive index adjustment of the film layer. The maximum reflectance of the coating is only 0.32 % over the entire visible wavelength range, and its average reflectance reaches an ultra-low level of 0.14 %. The coating has a wide angle anti-reflective performance. When the angle of incidence is <60°, the reflectance of the coating is <3 %. The results of this study are expected to provide direction for later experimental improvements.

Monolithic nanocellulose films patterned with flower-shaped and other microstructures: A facile route to modulate topographical, wetting and optical properties

Surface microstructures are found in nature as a mean to control wettability and adhesion. Efforts to reproduce related architectures in designing functional materials, however, require the use of tedious procedures, such as micro- and nanolithography. Herein, we introduce a facile and scalable method to create highly ordered surface microstructures or patterns supported on films made from the same material, cellulose nanofibrils (CNF). The micropatterning is based on fluid flow through solid grids that transfer three-dimensional designs on the surface of the formed films, with precise control on their spatial distribution. The obtained patterned films can be modulated as far as their wettability, optical and haptic features. The viscosity of the CNF aqueous suspension and strength properties of the produced films are shown to define the architecture of the surface patterns. In particular, multi-scale flower-shaped structures generate new properties, going from super-absorbency through capillary action in unmodified films to superhydrophobic materials after mild hydrophobization treatment. Our results pave the way to scalable and cost-efficient designs based on CNF for water harvesting, microfluidics, anti-reflective surfaces and haptic devices, among others

Optical modeling and characterization of bifacial SiNx/AlOx dielectric layers for surface passivation and antireflection in PERC

AbstractIn this research, we analyzed the impact that the optical characteristics of dielectric surface passivation and antireflection coating schemes have on the performance of passivated emitter and rear cell (PERC) silicon solar cells. We employed wafer ray tracer (WRT) and automate for simulation of heterostructure (AFORS‐HET) simulations, as well as experimental characterization of fabricated thin film coatings. We investigated three distinct front surface morphologies: planar surface, upright pyramids, and inverted pyramids. Using WRT, we calculated the photogeneration current densities (JG) for PERC devices with three schemes: (i) SiNx/AlOx as antireflection coating and passivation stacks on both the front and rear sides, (ii) SiNx antireflection coating on the front side and AlOx passivation layer on the rear side, and (iii) SiNx/AlOx as antireflection coating and passivation stacks on the front side with an AlOx passivation layer on the rear side. Following simulation with optimal JG, two schemes are experimentally evaluated: PECVD SiNx (70 nm) and atomic layer deposition (ALD) AlOx (15 and 25 nm). We confirmed the growth effects and optical properties using X‐ray diffraction, Raman spectroscopy, effective lifetime, and refractive index measurements. The most favorable electrical properties were obtained with SiNx (70 nm, front) and AlOx (25 nm, front and rear), where the AlOx can be deposited via ALD bifacially on a single step, minimizing processing while maintaining passivation performance. Finally, we used AFORS‐HET to simulate the maximum performance of PERC bearing such films. The results showed a Voc = 0.688 V, Jsc = 41.42 mA/cm2, FF = 84%, and packing conversion efficiency (PCE) = 24.12% as the optimal solar cell performance values.