Antireflective Films Research Articles

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.

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.

Superhydrophobic Modification of Atomic Layer Deposition Antireflection Aluminum Oxide Film: A Simple Evaporative Coating Technique.

The antireflective transmittance-enhancing films have important applications in solar cells and other applications due to their self-cleaning and high light transmittance. However, obtaining high transmittance, highly durable, and superhydrophobic surfaces in a simple and easily accessible way is still a challenge. A simple evaporative coating technique has been proposed that can be used to prepare antireflective superhydrophobic aluminum oxide films using 1H,1H,2H,2H-perfluoroalkyltriethoxysilanes. The results show that the contact angle of grass-like alumina increased from 99.5° to 155°. The surface energy of grass-like alumina decreased from 17.96 to 1.93 mN/m. The maximum value of light transmittance is close to 98%, and the average transmittance is above 95%. The films have excellent ultraviolet resistance and thermal stability along with relative mechanical and chemical stability. Meanwhile, this method has an excellent capacity for shape preservation. The relationships between the evaporation temperature and time and the light transmittance and hydrophobic angle of the films were also investigated together. This approach has the potential to be extended to large-scale industrial production.

Reconfigurable Antireflection Coatings Enabled by PDMS Oligomer Infusion in Templated Nanoporous Polymer Films.

The diffusion of uncured polydimethylsiloxane (PDMS) oligomers out of bulk PDMS elastomers is usually detrimental to many biomedical and microfluidic applications due to the inevitable contamination of the contacting fluids and substrates. Here, we transform this detrimental process into an enabling technology for achieving novel reconfigurable antireflection (AR) coatings, which are of great technological importance in the development of new nano-optical and optoelectronic applications. Self-assembled monolayer silica colloidal crystals are first used as sacrificial templates in fabricating nanoporous polymer AR coatings. When air in the templated nanopores is replaced with infused PDMS oligomers simply by pressing a PDMS stamp on a nanoporous AR film, the original antireflection conditions are lost, and the coating transforms from a low-reflection configuration to a high-reflection state. The original antireflection performance can be fully recovered by dissolving the infused oligomers in the appropriate solvents (e.g., hexane). This novel tuning mechanism for achieving reconfigurable AR properties has been confirmed by systematic investigations using various microscopes, optical spectroscopy, nanoindentation, thermomechanical tests, and X-ray photoelectron spectroscopy. Complex micropatterns with micrometer-scale spatial resolution and drastically different AR performances can be easily printed on nanoporous AR films by using a soft lithography-based microcontact printing process. Numerical finite-difference time-domain simulations match well with experimental antireflection measurements and reveal a linear relationship between the optical transmission and the amount of infused PDMS oligomers in nanopores.

Synthesis of hydrophobic silica without traditional aging process to construct the anti-reflective film with ultralow refractive index for improving power conversion efficiency

The fabrication of anti-reflective films to optimize sunlight utilization encounters various challenges. Herein, we have synthesized modified silica with hydrophobic properties, eliminating the conventional aging process to create an anti-reflective film with an ultralow refractive index of 1.05, marking the lowest value reported to date. This innovative methodology reduces tasks that typically require days or weeks to just a few hours, thereby significantly accelerating production. The power conversion efficiency of the photovoltaic device can increase by 6.2 % when coated with this film. This research not only advances the synthesis of silica but also develops anti-reflective films with record-low refractive indices. This breakthrough represents a substantial contribution, highlighting its significant impact on the photovoltaic field.

Enhancing terahertz magneto-optical effects in wafer-scale RIG single crystal thick films with anti-reflective coatings for improved transmittance

Wafer-scale rare-earth iron garnet (RIG) single crystal thick films were fabricated on 3-in. gadolinium gallium garnet (GGG) substrates using liquid phase epitaxy. The terahertz transmittance of the RIG crystals improved after removing the GGG substrate by polishing. The time-domain spectra at Terahertz (THz) frequencies indicate the existence of a magneto-optical effect in RIG samples. The results indicate that the RIG samples exhibit a high refractive index of ∼4.50 within the 0.1–1.0 THz frequency range, a transmittance of around 40%, and an absorption rate of only 10–50 cm−1. The Faraday rotation angles of the thick single-crystal films of the RIG samples were measured using a THz-TDS system. The RIG has a thickness of ∼330 μm. The Faraday rotation angles of RIG crystals at THz frequencies can reach up to 16° when an external magnetic field of 0.18 T is applied. The Verdet constants of the RIG sample were calculated to be ∼120°/mm/T. To improve the transmittance of the RIG sample, epoxy resin and polymethylpentene (TPX) were used as anti-reflective films. The transmittance of the RIG sample increased by ∼5% for the 80 μm thick epoxy and about 10% for the 320 μm thick TPX. Therefore, this RIG single crystal thick film can achieve a low loss, a high transmittance, and a strong magneto-optical effect in the terahertz region with the cooperation of a reflection-reducing film. It is expected to have wide applications in terahertz magnetic polarization conversion, non-reciprocal phase shifters, and isolators.

5.3 W/265 μJ Mid-IR All-Fiber Er3+:ZBLAN Gain-Switched Laser Based on Dielectric Fiber Mirror and Fiber-Tip Protection

We report a 2.8 μm all-fiber high-power and high-energy gain-switched Er3+:ZBLAN laser based on dielectric fiber mirror and fiber-tip protection. The fiber pigtail mirror, specifically designed for dichroic operation (i.e., anti-reflection at 976 nm pump wavelength and high-reflection around 2.8 μm laser wavelength), shows high damage density of >10 MW/cm2. An anti-reflection protective film is coated on the input tip of Er3+:ZBLAN fiber and an AlF3 endcap is spliced to the output tip of Er3+:ZBLAN fiber for mitigating the fiber-tip photodegradation and high-power catastrophic failure at 2.8 μm. The compact all-fiber cavity is formed by efficiently connecting the Er3+:ZBLAN fiber with dielectric fiber mirror using the standard FC/PC fiber adaptor. When the 976 nm pump operates in pulsed regime, the all-fiber mid-infrared gain-switched laser can be attained with two states of single-pulse and pulse-burst output. The extracted maximum pulse energy is 4.8 μJ in the single-pulse state, and the shortest pulse width is 426 ns. The pulse-burst mode can generate a maximum average power of 5.291 W and burst energy of 264.55 μJ. This work may offer a promising way to realize the low-cost, all-fiber, high-power and high-energy gain-switched laser at MIR wavelengths.

Synthesis of copper oxide (CuO) via coprecipitation method: Tailoring structural and optical properties of CuO nanoparticles for optoelectronic device applications

Oxide-based nanoparticles have been studied extensively due to their unique optical and passivation properties, which are significantly distinct from those of bulk materials. The present study aimed to synthesize copper oxide nanoparticles through the co-precipitation method. The adequate substitution of sodium hydroxide (NaOH) into CuO is analyzed by different characterizations, i.e., X-ray diffraction (XRD), Scanning Electron Microscope (SEM), UV–visible spectroscopy (UV–visible), Fourier transform infrared (FTIR), and EDX. The X-ray diffraction spectra indicate that the prepared copper oxide nanoparticles were crystalline, nano-sized, and highly pure. The SEM micrographs showed that nanoparticles were spherical at lower contents of NaOH, while at higher contents, agglomeration of nanoparticles occurs, and the grain size changes. The decreased optical bandgap of the nanoparticles was observed due to different concentrations of sodium hydroxide. The crystalline size and strain values were also determined through the Williamson-Hall method. The compressive micro-stain in CuO materials confirms the negative slope value of the line fit in the W–H Plot. From this study, we concluded that synthesized CuO NPs have the potential to combine CuO materials with antireflecting films for improved optical performance in optoelectronic devices, precisely current density properties.

Superhydrophilic antireflection films with excellent optical and mechanical performance for perovskite solar cells

SiO2-based antireflection (AR) films can obviously improve the transmittance of the glass cover on the solar cells. Nevertheless, it’s still challenging to fabricate SiO2 films in a facile way with great antireflective properties, high hardness and good weather resistance to ensure their long-term use in outdoor environments. To solve this problem, a double-layer broadband SiO2 antireflective film with high transmittance increase and excellent mechanical properties was successfully prepared via an acid-catalyzed sol–gel method using polyethylene glycol (PEG) as pore-forming agent. The porous PEG2000-modified SiO2 films were selected as the outer layer for coating onto the pure SiO2 film to form double-layer SiO2 films with graded refractive index. When the mass ratio of PEG2000 to TEOS was 40 %, the obtained film showed the highest transmittance increase of 3.03 % in the wavelength range of 380–1100 nm and a high hardness of 3H. After applied to the perovskite solar cell, a significant enhancement of 1.19 % in photoelectric conversion efficiency (PCE) was achieved compared to the solar cell covered with bare substrate. Furthermore, the water contact angle (WCA) was also reduced to 6° while that of pure SiO2 film was 51.3°, endowing the double-layer SiO2 film superhydrophilic and anti-fogging performance. After the weather resistance test, the transmittance loss of the film was only 0.38 %. Therefore, this work demonstrated that the use of an appropriate amount of pore-forming agent PEG and the double-layer graded refractive index structure can enhance the transmittance of acid-catalyzed SiO₂ films, while maintaining high hardness and good weathering resistance for perovskite solar cells.

Effect of magnetron sputtering power on the properties of the AlO X monolayer and AlO X /MgF2 bilayer anti-reflection films

The AlO X monolayer anti-reflection (MLAR) films and the AlO X /MgF2 bilayer anti-reflection (BLAR) films were deposited on high-purity glasses with magnetron sputtering. We investigated the influences of sputtering power on the O/Al molar ratio, microstructure, and optical properties of the AlO X MLAR films and AlO X /MgF2 BLAR films. The results showed that a too high or a too low sputtering power was detrimental to the preparation of the high-quality films, which could only be obtained when the sputtering power was 115 W. However, the sputtering power did not affect the crystallinity of the films, all of which were amorphous. When the sputtering power was 115 W, the high-purity AlO X MLAR film exhibited an O/Al molar ratio of 2.27:1, a refractive index of 1.426, and an average transmittance (T avg: average transmittance of the quartz glass deposited the film, hereinafter the same) of 94.03% within 300–1100 nm wavelength range. The T avg of AlO X /MgF2 BLAR film with a power of 115 W was 94.99%, which was 1.92% higher than that of the glass substrate. And it improved the cell’s photoelectric conversion efficiency (PCE) by 3.19%.

Design of ZnS nanospheres antireflective structure for mid and far infrared applications

Developing high-performance mid and far infrared antireflection films is a significant requirement in the field of infrared optics. This study successfully prepared AR films composed of ZnS nanospheres for mid and far infrared bands using a combination of hydrothermal and sol-gel methods. Initially, ZnS nanospheres with uniform size and good monodispersity were synthesized via the hydrothermal method and subsequently coated on CdSe substrate through dip coating. The refractive index of the ZnS film is adjusted between 1.36 and 1.52. A significant AR effect was observed in ZnS nanospheres film on CdSe substrate at 3–5 μm and 8–14 μm, and the reflectance is approximately 3 % which is about 25 % lower than that of the uncoated sample. Upon coating with a TiO2 protective layer, the reflectivity further decreased to about 0.6 % and the film demonstrated excellent weather resistance and mechanical properties. This work provides a novel approach for the preparation and regulation of mid and far infrared AR film, significantly contributing to the development of optical film.

Facile sol-gel synthesis of highly durable anti-reflection films with enhanced self-cleaning performance for perovskite solar cells

Facile sol-gel synthesis of highly durable anti-reflection films with enhanced self-cleaning performance for perovskite solar cells

Fabrication and characterization of MgF2 anti-reflective films comprising dual-layer prepared by physical vapor deposition technique for optoelectronic applications

Moth eye protuberances, for instance, exhibit highly developed and well-organized nanostructures that allow them to adapt to a wide range of environmental conditions and achieve remarkable antireflective performance, which has inspired and been emulated by scientific advancement. Innovative studies have focused on bioinspired and imitating moth-eye patterns to provide a textured surface in multilayer antireflective coatings (ARC) using nanomaterials, polymers, or composites to eliminate undesired reflection in standard optical components and optoelectronic industrial applications. Multilayer AR systems provide a number of advantages over single-layer designs. Still, their limited applicability is due to obstacles such as mismatched properties at interfaces, high costs, poor mechanical durability, and wetting concerns. Using MgF2 and polytetrafluoroethylene, we develop a technique for fabricating high-performance AR nanostructures on borosilicate crown glass and Fluorine-doped Tin Oxide substrates via the glancing angle deposition technique. By inducing porosity and changing the deposition angle (α) at 550 nm, the refractive index of MgF2 is reduced from 1.38 to 1.14. In agreement with optical modelling predictions, high-performance ARC has been successfully produced on different substrates. Besides this, introducing a thin layer of polytetrafluoroethylene on MgF2 ARC via vapor deposition having a refractive index of 1.21 deposited at α ∼80° results in inducing water-repellent properties in ARC. Hence, our fabricated ARC yields stable AR efficiency with outstanding directional uniformity, durability, and negative temperature stability, having hydrophobic characteristics.

Enhanced optical performance of solar cell using hydrophobic SnO2/TEOS/MTMS antireflection coating

AbstractAnti‐reflection coatings have potential usage in photovoltaic solar cells, sensors, and display devices to reduce reflectance, glare and enhance light transmission. ARC was developed to increase more efficiency of solar cell cover glasses, by depositing SnO2/TEOS/MTMS coating using the sol–gel spin coating technique. The coating showed a maximum transmittance of 92.70% at 399 nm wavelength with an average refractive index of 1.42. The transmittance of the antireflective film was increased by 2.29% than the bare glass substrate. The surface morphology of the coatings was investigated using FESEM analysis. The mechanical stability of the coating was evaluated using ASTM standard D 3363–05 pencil scratch test, and it demonstrated good performance against 3H hardness pencil. The efficiency of solar cells has been increased by 1.56% after depositing with single layer SnO2/TEOS/MTMS film. Moreover, the coating maintains the solar cell's performance even during dust exposure, because of its self‐cleaning ability with water contact angle of 94°. Thus, the Anti‐reflection coating can be applied to enhance the efficiency of photovoltaic system.

Double layer silica antireflective films with high strength and rub resistance prepared by sol gel method

The single-layer silica antireflective film with base catalysis prepared by sol gel method is an important part of the high-power laser facility for inertial confinement fusion, while the weak adhesion between the single-layer silica film and the substrate during the preparation process makes it susceptible to be contacted erasure and unable to be used. Double-layer silica antireflective (DLAR) films of different thicknesses were obtained using the base catalysis sol–gel method, in which the upper layer was coated with a relatively dense thin layer, and the performances of the films were characterized. The results showed that the transmittances of the DLAR films with different thicknesses were ˃99.0%, and in which one of the maximum transmittance peaks reached to 99.83% @ 1000 nm. The surface roughness of the DLAR films was < 2.0 nm, and the surfaces of the films were flat. The contact angles between DLAR films and water reached 118° and maintained stable in high humidity environment. The laser induced damage thresholds for different thickness DLAR films (peak transmittances @ 400, 600, 800, 1000 nm) were comparable to device requirements by 1-on-1 testing method, and the DLAR films exhibited high strength and good friction resistance.Graphical abstract

Comparative Study of Plasma-Enhanced-Atomic-Layer-Deposited Al2O3/HfO2/SiO2 and HfO2/Al2O3/SiO2 Trilayers for Ultraviolet Laser Applications.

High-performance thin films combining large optical bandgap Al2O3 and high refractive index HfO2 are excellent components for constructing the next generation of laser systems with enhanced output power. However, the growth of low-defect plasma-enhanced-atomic-layer-deposited (PEALD) Al2O3 for high-power laser applications and its combination with HfO2 and SiO2 materials commonly used in high-power laser thin films still face challenges, such as how to minimize defects, especially interface defects. In this work, substrate-layer interface defects in Al2O3 single-layer thin films, layer-layer interface defects in Al2O3-based bilayer and trilayer thin films, and their effects on the laser-induced damage threshold (LIDT) were investigated via capacitance-voltage (C-V) measurements. The experimental results show that by optimizing the deposition parameters, specifically the deposition temperature, precursor exposure time, and plasma oxygen exposure time, Al2O3 thin films with low defect density and high LIDT can be obtained. Two trilayer anti-reflection (AR) thin film structures, Al2O3/HfO2/SiO2 and HfO2/Al2O3/SiO2, were then prepared and compared. The trilayer AR thin film with Al2O3/HfO2/SiO2 structure exhibits a lower interface defect density, better interface bonding performance, and an increase in LIDT by approximately 2.8 times. We believe these results provide guidance for the control of interface defects and the design of thin film structures and will benefit many thin film optics for laser applications.

A novel optical management layer with flexible color tunability and high transmittance in organic solar cells

The evaluation of colored semi-transparent organic solar cells (ST-OSCs) relies on the power conversion efficiency (PCE) and peak transmittance across the visible light spectrum. However, it is a significant challenge to enhance both parameters simultaneously. In this study, we investigate the impact of different film systems for the Ag electrode on transmittance enhancement using an optical interference formula derived for anti-reflective films. As a result, a novel ZnS/WO3 double-layer anti-reflective film is introduced as an optical management layer. The ZnS/WO3/Ag structure achieves a peak transmittance exceeding 75 % across the visible light spectrum while also offering customizable color attributes. Upon electrical simulation, the power conversion efficiency (PCE) of organic solar cells with 15 nm Ag and 80 nm PM6:Y6 reached to 11.72 %, and an ideal PCE value of 14.53 % is achieved by reducing non-radiative recombination. Through optical simulations, it has been demonstrated that the integration of a ZnS/WO3 double-layer anti-reflective film with organic solar cells enables the generation of OSCs in vibrant purple, blue, cyan, and green hues. Notably, these OSCs exhibit their highest peak transmittance at blue light (452.5 nm), reaching an impressive value of 50.49 %. These remarkable findings not only showcase exceptional performance but also highlight significant potential in applications involving colored OSCs utilizing the new optical management layer composed of ZnS/WO3 double-layer anti-reflective films.

Porous SiO2 antireflection film with high UV resistance

Sol-gel is one of the most economical methods to prepare antireflection films, but the low ultraviolet radiation-resistance (UV-resistance) of the sol-gel film limits its applicability in the solar industry. A SiO2 antireflection film was prepared with sol-gel method with phenyl salicylate (PS) as the porogen. The effects of the PS addition were investigated on the microstructure, optical property and UV-resistance of the film. When the addition of PS is 1.20 g, the refractive index at 550 nm is 1.30, and the maximum transmittance is 96.30 %. The average transmittance within the 400–1100 nm range reaches its peak at 92.85 %, which is 4.35 percentage points higher than that of the blank glass. In addition, the film without PS has an average transmittance of 91.00 % after 5000 equivalent solar hours (ESHs) UV irradiation, decreasing 1.07 percent point, and has a pencil hardness of 5 H and an adhesion of grade 2 of the tape-tearing method. However, the film with 1.20 g of PS still has an average transmittance of 92.15 % after 5000 ESHs UV irradiation, decreasing only 0.7 percent point, and has a pencil hardness of 7 H and an adhesion of grade 1 of the tape-tearing method.

A linearly polarized light emission with a composite nanowire grating in whole white band

To obtain a highly linearly polarized light, a composite model consisting of white light emission, anti-reflection film, and metal-dielectric-metal nanowire grating was designed, analyzed, optimized, and fabricated. Based on the finite-difference time-domain method, the impacts of material, period, height, and incidence angle on the polarization performance of the composite model were discussed. The metal-dielectric-metal nanowire grating was fabricated on blue chip and fluorescent ceramics using nanoimprint technology. The employed materials of metal-dielectric-metal nanowire grating were aluminum and PMMA, with the period of 200 nm, wire width of 100 nm, and the height of metal and dielectric were 100 nm and 120 nm. Additionally, the anti-reflection film consisting of PMMA with the thickness of 45 nm was incorporated on fluorescent ceramics to enhance energy efficiency. Finally, through a series of test experiments, the composite model can be realized by the extinction ratio of 40 dB, while the transmittance of TM mode exceeds 50% at 450–750 nm. The theoretical analysis of this study is verified by experiments, and it has significant potential in the pursuit of high brightness, ultra-thin micro displays.

Achieving effective performance of silicon solar cell through electrosprayed MgF2 antireflection coating

Solar cells technology will be one of the futuristic major resources for global energy demands. One of the major problems in energy harvesting using solar cells was reflection of incident light over solar cell surface. The present research work aims to synthesize the magnesium fluoride through sol-gel process which acts as antireflection layer for achieving better output performance. MgF2 films were deposited over solar cells at varying time periods of 60, 90, 120 and150 min through electrospraying technique. MgF2 electrosprayed solar cells were inspected for evaluating its structural, optical, electrical and morphological characteristics. The coated solar cells were analyzed under dark and light conditions. The precursor materials involved in sol-gel synthesis of MgF2 were magnesium chloride hexahydride, polyethylene glycol and hydrofluoric acid. From the I–V results, it is evident that performance of 120 min MgF2 coated solar cell exerts maximum performance of 19.38 % (open) and 19.41 % (controlled). MgF2 antireflective electrosprayed films were prominent materials for minimizing reflection and ensuring the maximum photon transmission into the coated surface especially in opto-electronic applications.