Antireflection Characteristics Research Articles

Enhanced Photovoltaic Efficiency through 3D-Printed COC/Al₂O₃ Anti-Reflective Coversheets

In the past few years, there has been a considerable growth in the utilization of solar cells to produce electrical power to fulfil the growing worldwide energy demands. An optical loss is a crucial factor that impacts the performance of the photovoltaic conversion process. This loss occurs when incoming sunlight is reflected back on the outer layer of the photovoltaic cells. The application of antireflective materials on the photovoltaic substrates can enhance the absorption of sunlight and minimize the reflection. Currently, there is no ideal anti-reflective coating for solar cells that can allow the transmission of sunlight without any reflection. In this research, a transparent cyclic-olefin-copolymer (COC) was used to fabricate anti-reflection (AR) coversheet by fused deposition modelling process (3D printing). Further, the aluminium oxide Al2O3 powder was added at the proportions of 1wt%, 2wt%, 3wt%, and 4wt% to the COC polymer to increase the anti-reflection characteristics. The structural, morphological, mechanical (tear strength), electrical and temperature characteristics were studied. The performance of COC with aluminium oxide (COCA) coversheets was evaluated, and the findings revealed a considerable increment in power conversion efficiency (PCE) of 17.21% (sunlight exposure) and 18.34% (neodymium light) for COCA3 coversheets. As seen, the COCA3 sample exhibit lower electrical resistance of 3.88 ×10-3 Ω cm, carrier concentration (36.91×1020 cm-3) and higher hall mobility (13.67 cm2/Vs). The findings from the investigations demonstrated that the utilization of COC with Al2O3 powder (COCA) can be a suitable antireflective coversheet material for boosting the performance of polycrystalline silicon photovoltaic cells.

Fabrication of black metal surface for high solar energy absorption by femtosecond laser hybrid technology

Metals are crucial for solar energy applications, but their highly reflective surfaces limit solar energy absorption. The difficulty in manufacturing an ideal light-absorbing structure limits the incorporation of anti-reflective characteristics in metals. In this study, a femtosecond laser method was introduced to form micro-nano structures in metals, enhancing absorption by the application of silver nanoparticles and resulting in solar absorption rates of 97.2%, 98.3%, and 98.9% for aluminum, titanium, and steel, respectively. The solar reflectance was reduced by 82.3%, 62.6%, and 79.2%, respectively, compared to bare metal. Photothermal conversion and deicing tests verified a more efficient photothermal conversion ability in the composite micro-nanostructure surface. Compared to bare metal, the structure has more than twice the solar absorption efficiency and improves the deicing efficiency by 132%. The resultant material exhibits high photothermal conversion and deicing efficiencies, enhancing its potential for solar energy applications, particularly in photothermal, photovoltaic, and thermal solar technologies.

Tailored nano-pillar structures on surfaces: facile formation and multifunctional properties

Nano-pillar structured surfaces have prized for exceptional optoelectronic properties and biocompatibility but commonly complex, expensive, and inflexible in production. A systematic investigation of the formation, mechanisms, and properties of nanostructures induced by nano-capillaries remains unexplored. Through this study, the facile formation of nano-pillared surfaces induced by designable nano-capillaries on AAO template demonstrated significant improvements in antibacterial effect, spectral structural color and anti-reflection characteristics. Reverse molding of nano-pillar arrays with aspect ratios of up to 1.2 on polydimethylsiloxane (PDMS) films yielded a super-hydrophobic surface of 150° contact angle (CA). Through the utilization of computational fluid mechanics model, a direct correlation was demonstrated between the aspect ratio of nano-pillars and the viscosity of PDMS. The nano-pillared surfaces had remarkable antibacterial rates of 91% for Escherichia coli and 89% for Staphylococcus aureus. In addition, the structured surfaces exhibited color spanning from light blue to light red by tuning nano-pillars dimensions, incident light angle, and/or adding reflective metallic coating, which offered unique visualization effects for anti-counterfeiting. Moreover, the superior light-trapping and anti-reflection of the nano-pillared surface significantly increased the power conversion efficiency (PCE) 19% from the base performance of the polysilicon solar cells.

Design and deposition of ZnS antireflection coating for high-performance mid-infrared PbSe photoconductive detectors fabricated by chemical bath deposition

Enhancing the detectivity is still a challenge for uncooled mid-infrared PbSe photoconductive (PC) detectors. Antireflection coating (ARC) provides a convenient solution to this challenge. Herein, antireflection physical modeling was proposed based on microstructural features of PbSe PC detectors. The simulated results show that the surface roughness contributes to the absorption enhancement of PbSe detectors, which reflects the advantage of the chemical bath deposition (CBD) manufacturing technology. Meanwhile, being the optimal ARC choice, ZnS ARC with thickness from 300 to 420 nm could induce more than 20 % absorption improvements in coarse CBD-PbSe films, which is confirmed by a signal enhancement from CBD-PbSe PC detectors covered with ZnS ARC. Combing with a noise reduction, the peak detectivity (D*) is almost doubled from 0.8 × 1010 to 1.5 × 1010 cm‧Hz1/2‧W−1 after depositing a desired ZnS ARC. Furthermore, ZnS ARC significantly eliminates the performance degradation of detectors triggered by moisture in the air. The low-cost ZnS ARC with good repeatability, which combines the characteristics of antireflection and passivation, provides an available solution to promote the industrialization of PbSe PC detectors.

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.

Anti-reflective properties of butterfly-wing-micro-nano structures in the infrared band

The delicate and intricate micro-nano structure on the surface of butterfly wings is genuinely remarkable. Despite its potential for anti-reflection purposes, this surface structure's theoretical analysis, optimal design, and anti-reflection performance regulation remain a mystery. The anti-reflection characteristics of butterfly Papilio epiphorbas, butterfly Parthenos syvia, and butterfly Sasakia charonda butterfly wings in the infrared band were carefully examined using finite difference time domain simulation and equivalent medium theoretical calculation. The anti-reflection mechanism of the surface micro-nano structure parameters and infrared wavelength of the butterfly wings of butterfly Papilio epiphorbas, butterfly Parthenos syvia, and butterfly Sasakia charonda were revealed. By Fourier infrared reflectance test and simulation of the three butterfly wings, the results show that the structural color scales of the three butterfly wings can achieve a better anti-reflection effect in the infrared band. The anti-reflection performance of the extracted bionic butterfly wings is improved by 0.34%, 2.44%, and 5.46%, respectively, compared with the original butterfly wings. These findings provide valuable theoretical and data support for the continued development of the design and manufacture of bionic anti-reflective surface optics.

Leafhopper-inspired reversibly switchable antireflection coating with sugar apple-like structure arrays

Optical coatings with reversibly tunable antireflective characteristics hold a tremendous potential for next generation optical energy-related applications. Bioinpsired by the camouflage behavior of small yellow leafhoppers, silica hollow sphere/shape memory polymer composites are self-assembled using a non-lithography-based approach. The average visible transmittance of the as-patterned hierarchical structure array-covered substrate is increased by ca. 6.3% at normal incident, and even improved by more than 20% for an incident angle of 75°. Interestingly, the broadband omnidirectional antireflection performance can be reversibly erased and recovered by applying external stimuli under ambient conditions. To gain a better understanding, its reversibility, mechanical robustness, and the structure-shape effect on the antireflective properties are systematically investigated in this research.

Comparative optical analysis of GaAs nanostructures for photovoltaic applications using finite element method

In this manuscript, a thorough comparative analysis of six GaAs based nanostructures (hollow and solid) is performed on the basis of their optical performance. These nanostructures are known to exhibit excellent anti-reflection properties, owing to their ability to generate a broadband absorption spectrum through efficient photon harvesting. Using the Finite Element Method (FEM) of the commercially available COMSOL Multiphysics package, the absorption characteristics, optical short circuit current density (JSC), electric field and photogeneration rates of six different nanostructures namely concentric nanocylinder (CNCy), hollow concentric nanocylinder (HCNCy), inverted nanopencil (INPe), hollow nanopencil (HNPe), nanorod + nanohemisphere (NR + NHe), and hollow nanorod + hollow nanohemisphere (HNR + HNHe) are computed. The optical performance of these nanostructures is largely dependent on their geometrical parameters such as filling ratio (FR = Diameter/Period), spacing and structural dimensions. The optimized values of these parameters can play a vital role in capturing the optical resonance modes by the nanostructures to produce absorption enhancement. It has been observed that the nanostructures with base diameter of 240 nm, period in the range of 300–350 nm and FR of 0.8 exhibit better optical characteristics. Optical JSC and optical efficiency of 29.45 mA cm−2 and 42.26%, respectively for CNCy nanostructure with FR of 0.8 and diameter of 240 nm is the highest among all the nanostructures. The effect of the angle of incidence of the photons striking the nanostructures on the average absorptance in both Transverse Electric (TE) and Transverse Magnetic (TM) modes are also investigated. In addition to this, we have also computed the effective refractive index for all the nanostructures using Maxwell Garnett formula in order to estimate the surface anti-reflection characteristics of these nanostructures.

Theoretical Simulation and Preparation of Anti-reflection Characteristics of Zinc Sulfide Surface Microstructure

Theoretical Simulation and Preparation of Anti-reflection Characteristics of Zinc Sulfide Surface Microstructure

Anti-reflecting metasurface for broadband polarization independent absorption at Ku band frequencies

An impedance matched metasurface can efficiently channel the electromagnetic fields for maximum power transfer. The thin film based impedance matching techniques often utilize highly dissipative materials and destructive interference of reflection components from multiple subwavelength layers. Here, we propose a novel method to achieve anti reflection characteristics through destructive interference of antiparallel electromagnetic scattering emerging from chiral metasurface. The supercell structure of metasurface consists of four adjacent multi split-rings on FR-4 substrate. The split-rings are arranged to induce anti-parallel surface currents leading to destructive interference for scattered fields. The antireflection characteristics results in near perfect broadband absorption at dual frequency bands. A broadband absorption of 983 MHz is achieved between 12.687 and 13.669 GHz. Similarly, a narrow band absorption of 108 MHz is achieved in frequency range of 15.307–15.415 GHz. The impedance matched with unique symmetric design of supercell results in identical absorption for both x- and y-polarized incident fields. The numerical and experimental results verify broadband absorption characteristics at Ku band frequencies. The proposed metasurface absorber can be used for microwave energy harvesting applications.

Broadband absorber coupled with anti-reflection inverted pyramid type all-dielectric microstructure

In order to improve the absorption efficiency and absorption bandwidth, we propose an inverted pyramid type all-dielectric absorber. Using the anti-reflection interface characteristics of the inverted pyramid microstructure, the designed absorber can achieve 100% perfect absorption in the range of 1.5THz to 1.7THz. Based on the structural diffraction analysis and electromagnetic field distribution characteristics, we have deeply explored the physical mechanism of wave absorption of the designed structure, and revealed the dual physical mechanism of electromagnetic wave diffraction conversion and resonance absorption. Based on the unique wet etching technology, we have experimentally prepared this inverted pyramid type all-dielectric absorber. Through experimental measurement, the consistency of the theoretical design and experimental test was confirmed.

Fabrication of random nanocones to improve wideband light trapping for thin film photovoltaic devices using nanosecond laser processing

Light-trapping is very crucial for thin film solar cells for the efficient collection of light to reach high light conversion efficiencies. Recently, the use of surface micro/nanostructure has emerged as a suitable technique to improve the absorption of light in thin solar absorbers. Amorphous silicon (a-Si) has strong absorption in the visible region. Expansion of this absorption band towards near infrared (IR) region by reducing the reflectance with light trapping has been presented in this in this work. This is achieved by fabricating random nanocones using laser texturing on the a-Si thin film surface. In this study, periodic structures with different shapes are theoretically investigated to identify the ideal texture shape for wideband light coupling and compared with the surface reflective properties of random nanocones. The light-trapping properties of random nanocones, fabricated using a ns pulsed Nd3+: YAG (neodymium-doped yttrium aluminium garnet) laser in water and air are investigated, and the influence of texture dimensions in improving the antireflection characteristics are studied. Numerical simulation shows the reduction in reflection in the near (IR) region with the random nanocones compared to regular periodic structures, overall exhibiting wideband antireflectance in ultraviolet (UV)–visible–near IR region due to the presence of multiscale structures. Experimentally measured reflectance across the whole spectra decreased by 14% to 19% in comparison with the untextured surfaces suggesting an enhancement in light coupling through multiple reflections on the laser fabricated nanocones. A small decrease of about ∼ 0.15 to 0.8% in efficiency was observed in the first one hour when continuously exposed to light in the thermal stability studies, and it remained stable for the rest of the test. This study will help in designing thin film solar absorber with a wide absorption range to aid in meeting the energy demand.

Tailoring the structural and optical properties of HiPIMS TiO2 thin films for photovoltaic applications

Titanium dioxide (TiO2) thin films are deposited onto glass and silicon <100> substrates by high power impulse magnetron sputtering (HiPIMS) at various substrate positions from the substrate-holder center (x = 0, 10, 20 and 30 mm). The structural analysis conducted through XRD and Raman spectroscopy shows that all the films deposited at lower radial distance (x = 0–20 mm) are identified as pure anatase phase of TiO2, while those deposited at 30 mm contain a small trace of rutile phase with anatase phase remaining dominant. AFM analysis reveals homogenous surfaces with low values of roughness (2.6–3.8 nm) and a decrease of grain size with the substrate position. The films exhibit high refractive index and large indirect optical band gaps (3.25–3.38 eV). Finally, UV-blocking and antireflection characteristics are studied.

Tunable antireflective characteristics enabled by small yellow leafhopper-inspired soccer ball-shaped structure arrays

BackgroundNowadays, tunable antireflective characteristics have attracted considerable attention due to growing demands in next-generation optical energy-related fields. MethodBioinspired by the distinctive structural geometry on small yellow leafhopper wings, this study reports reversibly switchable antireflective characteristics enabled by ambient-temperature shape memory polymer-based soccer ball-shaped structure arrays with multilayer porous structures underneath. Significant findsThe resulting structures behave a broadband omnidirectional antireflection performance, where the average reflectance in the visible spectrum can even be reduced by 22% for an incident angle of 75º. Interestingly, the structures can be instantaneously deformed or recovered through applying external stimuli in ambient environments. The antireflective property switches associated with the shape memory transitions deliver vast opportunities in developing smart optical devices. Moreover, the structure-shape effect and reversibility on the antireflective properties are systematically assessed in the research.

Dual-Band Helical Edge States and Discrete Dirac Vortices in Solid-State Elastic Waves

Dual-band equipment has unique advantages as regards ensuring the stability of wireless communication and improving efficiency. With the development of topological photonics and phononics, electromagnetic and mechanical wave transmission with simultaneous advantages, e.g., antireflection, broadband, and nondispersion characteristics, has been simultaneously realized. This outcome has greatly improved elastic wave manipulation performance in solids, which are important media for wireless communication. Here, using a plate phononic crystal (PnC), a dual-mode elastic topological insulator is theoretically designed and experimentally realized, and the quantum spin Hall effect is observed under a dual band. Using discrete Kekul\'e modulation to construct the PnC multidomain junction, dual-mode and dual-band Dirac vortexes, i.e., a type of topological corner state, are obtained in a single PnC. These transmitted and localized topological states have the same excellent properties as their antecedents, which are obtained with single-band materials. The implementation mechanisms are diverse and applicable to multiple modes and broad frequencies, offering antijamming, low-loss, high-efficiency, and high-capacity signal processing components. The findings of this study will aid development of solid-state topology PnCs, as well as future topological-phononic integrated circuits with high performance and multifunctionality.

Polarization-insensitive broadband omni-directional anti-reflection in ZnO nanoneedle array for efficient solar energy harvesting.

Broadband omni-directional anti-reflection characteristics have been an important issue because they can maximize the optical absorption in photovoltaic devices. Here, we investigate the optical properties of ZnO nanoneedle arrays to demonstrate broadband anti-reflection, omni-directionality, and polarization insensitivity using optical simulations and experimental approaches. The results of this work clarify that the ZnO nanoneedle array plays an important role as a broadband anti-reflection layer due to its spatially graded refractive index, omni-directionality and polarization insensitivity. To take advantage of these structures, we prepared a ZnO nanoneedle array on the surface of conventional SiNx/planar Si solar cells to prove the broadband omni-directional anti-reflection for solar energy harvesting. Current density–voltage results show that SiNx/planar Si solar cells with ZnO nanoneedle arrays lead to a nearly 20% increase in power conversion efficiency compared to SiNx/planar Si solar cells, and a 9.3% enhancement in external quantum efficiency is obtained under identical conditions. Moreover, the photocurrent results of SiNx/planar Si solar cells with ZnO nanoneedle arrays clearly demonstrate the incident angle- and polarization-insensitive characteristics compared to those of typical SiNx/planar Si solar cells. Our results demonstrate the optical multi-functionality of ZnO nanoneedle arrays and pave the way for high-performance optoelectronic devices that require broadband omni-directional anti-reflection and polarization insensitivity.

Efficient GaAs nanowire solar cells with carrier selective contacts: FDTD and device analysis

Nanowire (NW) solar cells (SCs) with III-V materials have demonstrated superior light harvesting and anti-reflection characteristics, while also consuming less material than planar SCs. However, the performance of NW-based SCs in actual applications falls short of expectations because to their high surface-to-volume ratio and short minority carrier lifetimes. To tackle this, core-shell radial junction SCs are proposed. However, it is extremely difficult to achieve precise doping in both core and shell of NWs while preserving defect-free interface characteristics in the experimental realization, resulting in poor p-n junction quality and significant recombination processes. In this article, we have proposed a core-shell heterojunction SCs composed of p-type GaAs NW as the core material and ITO/TiO2 as the shell material to achieve high efficiency. Using the finite-difference time-domain (FDTD) methodology, we have shown that a coating of ITO/TiO2 shell over a geometrically optimized GaAs core may considerably reduce the cell's optical losses. In addition, using Lumerical's Charge solver module we found that the use of n-type TiO2 coating as an electron-selective can significantly improve the minority carrier transport and collection in the device. The optimized structure has exhibited an efficiency of 18.43% even for low minority carrier life-time (τn) of 100ps and carrier mobility (μn) of 1000cm2V−1s−1 while maintaining high surface recombination velocity (SRV) of 107 cm/s and 104 cm/s at contacts and TiO2/GaAs interface, respectively.

A Composite Matching Layer with Anti-Reflection Characteristics for Broadband Acoustic Scattering Reduction

A composite matching layer composed of periodically arranged scatters with anti-reflection (AR) characteristics is proposed for broadband scattering reduction. The anti-reflection structure is composed of periodically arranged metal foam scatters, and it is the first attempt to be applied in the field of suppressing acoustic reflection. A complete theoretical model is developed to reveal the mechanism of scattering reduction and acoustic absorption based on effective medium theory and the transfer matrix method. The correctness and effectiveness of the theoretical model are verified by the finite element method (FEM), showing acoustic reflectance of less than 13.5% at broadband frequencies. The variation trends of reflectance are deeply investigated. The superior acoustic scattering reduction performance suggests that the matching layer possesses potential for acoustic imaging equipment and acoustic stealth.

Fabrication of Needle-Like Silicon Nanowires by Using a Nanoparticles-Assisted Bosch Process for Both High Hydrophobicity and Anti-Reflection.

In this work, a modified Bosch etching process is developed to create silicon nanowires. Au nanoparticles (NPs) formed by magnetron sputtering film deposition and thermal annealing were employed as the hard mask to achieve controllable density and high aspect ratios. Such silicon nanowire exhibits the excellent anti-reflection ability of a reflectance value of below 2% within a broad light wave range between 220 and 1100 nm. In addition, Au NPs-induced surface plasmons significantly enhance the near-unity anti-reflection characteristics, achieving a reflectance below 3% within the wavelength range of 220 to 2600 nm. Furthermore, the nanowire array exhibits super-hydrophobic behavior with a contact angle over ~165.6° without enforcing any hydrophobic chemical treatment. Such behavior yields in water droplets bouncing off the surface many times. These properties render this silicon nanowire attractive for applications such as photothermal, photocatalysis, supercapacitor, and microfluidics.

Tunable Omnidirectional Antireflection Coatings Inspired by Inclined Irregular Nanostructures on Transparent Blue-Tailed Forest Hawk Dragonfly Wings.

Randomly arranged inclined irregular nanostructure-covered blue-tailed forest hawk dragonfly wings are highly transparent for wide viewing angles. Inspired by the dragonfly wings, monolayer silica colloids are self-assembled on shape memory polymer-coated substrates and utilized as plasma etching masks to pattern disorderly arranged inclined irregular conical structures. The structures build gradual refractive index transitions at various angles of incidences, resulting in omnidirectional antireflection performance over the whole visible wavelength region. In comparison with a bare substrate, the optimized structure-covered substrate presents 10% higher optical transmission at 0° and even 41% higher optical transmission at an angle of incidence of 75°. Importantly, by manipulating the structural configuration of the shape memory polymer-based structures, the corresponding antireflection characteristics can be instantaneously and reversibly eliminated and recovered after drying out of common household liquids or applying contact pressures in ambient environments. The tunable omnidirectional antireflection coatings are prospective candidates for realizing optical modulation, which exhibits an enormous application value in smart windows, intelligent display screens, optical components, and novel optoelectronic devices.