Antireflective Films Research Articles

Micro-/nano-crater in ultraviolet-pulsed-laser irradiated anti-reflective film

To address the issues of laser-induced shadow pit in anti-reflective (AR) film, the characteristics of the micro-/nano-crater in AR films irradiated with different laser energies, and the effects of the crater on the film and the fused silica substrate were studied. The results indicate that craters may be present solely in the film layer, or both the film layer and the substrate. Precursors such as trace particles in the sol-gel solution may be the main factor causing the formation of micro-/nano-crater. Finally, two physical models are proposed based on the properties of craters. That is, (1) the heat absorption of precursors generates plasma micro-explosion, and (2) the effect of recoil momentum and confined plasma pressure. The processes and mechanisms of the crater formation are further elaborated.

Hydrophobic anti-reflective silica hybrid film with tunable refractive index

As one of the important optical films, the anti-reflection film can effectively reduce light reflection at the optical interface, and has wide application potentials in the fields of solar power generation, high-power laser systems, optical devices. However, besides high transmittance, strong environmental resistance and mechanical properties are also needed for anti-reflection coatings in practical applications. In this paper, a series of single-layer hydrophobic anti-reflection silica coatings with adjustable refractive index between 1.13 and 1.44 is obtained via the hybridization of hydrophobic-modified alkali-catalyzed silica hollow nanospheres with hydrophobic acid-catalyzed silica in different proportions, and then used for the construction of double-layer membranes where the top layer has a refractive index of 1.19 and the bottom layer has a refractive index of 1.25. The single-layer film can exhibit nearly perfect transmittance up to 99.2 %, and meanwhile, the double-layer film exhibits excellent broadband anti-reflection with an average transmittance of 98.7 % in the wavelength range from 300 to 900 nm. The hydrophobicity of these films is excellent, and the maximum water contact angle reaches 142°, so the dust pollution hardly leads to the decline of its optical performance. Moreover, the addition of acid-catalyzed sol improves the mechanical properties of the hybrid film while maintaining good transmittance even after the rubbing test.

Recent Applications of Antireflection Coatings in Solar Cells

The antireflection coating (ARC) suppresses surface light loss and thus improves the power conversion efficiency (PCE) of solar cells, which is its essential function. This paper reviews the latest applications of antireflection optical thin films in different types of solar cells and summarizes the experimental data. Basic optical theories of designing antireflection coatings, commonly used antireflection materials, and their classic combinations are introduced. Since single and double antireflection coatings no longer meet the research needs in terms of antireflection effect and bandwidth, the current research mainly concentrates on multiple layer antireflection coatings, for example, adjusting the porosity or material components to achieve a better refractive index matching and the reflection effect. However, blindly stacking the antireflection films is unfeasible, and the stress superposition would allow the film layer to fail quickly. The gradient refractive index (GRIN) structure almost eliminates the interface, which significantly improves the adhesion and permeability efficiency. The high-low-high-low refractive index (HLHL) structure achieves considerable antireflection efficiency with fewer materials while selecting materials with opposite stress properties improves the ease of stress management. However, more sophisticated techniques are needed to prepare these two structures. Furthermore, using fewer materials to achieve a better antireflection effect and reduce the impact of stress on the coatings is a research hotspot worthy of attention.

Coupled optical-electrical-thermal loss modelling and energy distributions of a photovoltaic module

This paper develops a coupled optical-electrical-thermal loss model of a photovoltaic (PV) module under various conditions. Validation shows that the coupled optical-electrical-thermal loss model is accurate and effective, ranging from 0.17% to −1.88%, which are smaller than limit error in the IEC standard. The developed model is then applied to investigate energy distributions of a PV module under standard test conditions (STC) and dynamic conditions by qualitative and quantitative evaluations. Results show that the energy distributions under dynamic conditions are similar to those under STC. The power output, optical and thermal losses are 16%, 16% and 68%, respectively. The optical losses mainly result from transmission loss (43.4%), reflection loss at air-glass interface (25.5%) and reflection loss at PV layer (25%). As for complicated thermal losses, they are caused by thermalization loss (38.4%), sub-bandgap loss (21.6%), angle mismatch loss (12.9%) and voltage drop loss due to non-radiative recombination (11.6%). Furthermore, some optical suggestions (anti-reflection film, velvet surface and light trapping structure) and thermal suggestions (up conversion, down conversion, stacked structure, surface recombination optimization and the photovoltaic/thermal technology) are proposed to optimize the PV power output.

Spectrally selective antireflection of nanoimprint lithography-formed 3D spherical structures on film coated with a silver layer

We fabricate moth-eye antireflection (AR) coatings using high-resolution and low-cost UV nanoimprint lithography with polyethylene terphthalate (PET) molds. Several various thicknesses of silver films placed on the moth-eye structure were analyzed for reflectance and transmission. On PET, the conical nanostructured surface arrays had a spatial period length of approximately 250 nm, a diameter of approximately 200 nm, and a height of approximately 160 nm. After them, a silver (Ag) layer of 18 nm is deposited satisfactorily on the PET substrate surface. The never-ending moth-eye formations of the imprinted mold were fabricated by Ni mold electroplating, interference lithography, and replication. We found that an Ag layer of suitable thickness on AR film in the spectrum range that can be seen has high transmittance (Highest value is 72%) while in the infrared spectrum it has high reflectance (At least 60%). For an optical film with a silver coating has been placed on an anti-reflection subwavelength-structured (ASS) surface, such properties, including heat insulation, have obvious applications in windows for homes and vehicles.

Solvothermal treatment of MgF2 coating solutions: a comparative study

MgF2 coating solutions were prepared by the fluorolytic processing of Mg(OEt)2 and MgCl2. Parts of these sols are solvothermally treated in an autoclave at 160 °C. The two respective precursors were used to prepare porous λ/4 antireflective films by dip-coating on soda-lime and borosilicate glass substrates. UV–Vis spectroscopy and X-Ray diffraction (XRD) were applied to characterize the films as a function of annealing temperature. Samples treated at 500 °C underwent testing of abrasion resistance and water solubility.Porous antireflective MgF2 coatings were prepared from as-synthesized solutions and sols that had additionally undergone solvothermal processing. Films prepared on soda-lime and borosilicate glass substrates were systematically compared.

Investigation of Hybrid Films Based on Fluorinated Silica Materials Prepared by Sol–Gel Processing

In this research, fluorinated silica materials were prepared through sol–gel processing with tetraethylorthosilicate (TEOS), triethoxymethylsilane (MTES), and trimethoxyhexadecylsilane (HDTMES), using a fluorinated solution (FS) under acidic medium. The fluorinated solution (FS) was obtained by diluting the perfluorooctanoic acid (PFOA) in 2-propanol. These fluorinated sol–gel silica materials were placed on the glass surfaces in order to achieve the antireflective and hydrophobic fluorinated hybrid films. The structure and surface properties of the final samples were investigated by Fourier transform infrared spectroscopy (FTIR), ultraviolet/visible spectroscopy, thermogravimetric analysis (TGA), atomic force microscopy (AFM), and contact angle (CA) determinations. FTIR spectra demonstrated the presence of a silica network modified with alkyl and fluoroalkyl groups. Thermal analysis showed that the fluorinated sol–gel silica materials prepared with HDTMES have a good thermostability in comparison with other samples. Ultraviolet/visible spectra indicated that the fluorinated hybrid films present a reflectance of ~9.5%, measured at 550 nm. The water contact angle analysis found that the wettability of fluorinated hybrid films was changed from hydrophilic (64°) to hydrophobic (~104°). These hybrid films based on fluorinated sol–gel silica materials can be useful in various electronics and optics fields.

Statistical information enhanced robust design method of optical thin film.

A novel merit function was constructed using the spectral coefficient average error and standard deviation, which can simultaneously optimize the expectation of spectral coefficient error and the envelope of standard deviation. Thus, a multi-objective optimization strategy based on Non-Dominated Sorting Genetic Algorithm and Sequential quadratic programming was proposed. By comparing result of wideband anti-reflection film, cut-off filter and Infrared dual-band filter designed by the conventional algorithm and the new algorithm, the control effect of the new algorithm on sensitivity of film parameters error was verified. The results show that the novel design method has the characteristics of time-efficient calculations and is capable of effectively improving the production yield of the film system, which has practical significance.

Neutron irradiation effect on amorphous porous silica

AbstractPorous silica is widely used as antireflection films in inertial confinement fusion facilities and be irradiated by high fluence neutron. To date, the neutron irradiation effect of amorphous porous silica is still unclear. In this paper, we give a comprehensive insight into neutron irradiation effect on microstructure, mechanical, and optical properties of porous silica under 14 MeV neutron irradiation by using molecular dynamics and density‐functional theory‐based methods. We find that, for microstructure, neutron irradiation elongates Si–O bond distance, obviously reduces the max value of Si–O–Si bond angle, coordination number distribution, and increases Si3+ and non‐bridging oxygen defects. The bulk modulus, shear modulus, and Young's modulus are all obviously reduced due to neutron irradiation, but Poisson's ratio changes relatively small. The light transmittance is reduced, and the optical absorption coefficient is increased after neutron irradiation, especially in the photon energy range of 3–4 eV, which is detrimental to the resistance of laser‐induced damage. Moreover, we find that neutron irradiation has more influence on high‐porosity porous silica than low‐porosity porous silica, which is mainly due to the higher defect percentage in high porosity. Present work is expected to be valuable in the study of degradation mechanism of nuclear material under neutron radiation.

Fabrication of Oxide Passivated and Antireflective Thin Film Coated Emitter Layer in Two Steps for the Application in Photovoltaic

Fabrication of Oxide Passivated and Antireflective Thin Film Coated Emitter Layer in Two Steps for the Application in Photovoltaic

Dependence of Structural and Optical Performance of Lanthanum Fluoride Antireflective Films on O Impurities

Lanthanum fluoride (LaF3) thin films were deposited on the Ge substrate using the molybdenum boat evaporation method. The effect of films’ oxygen impurity on the infrared optical properties has been investigated for the first time in this report. With the increase in oxygen content in the films, the F content decreases, and the O/F ratio decreases from 0.160 to 0.055. XRD patterns reveal that the presence of O impurity destroys the crystal structure integrity of the LaF3 films and leads to the intensification of infrared absorption. The average transmittance decreases from 58.1% to 52.2%, and the peak transmittance decreases from 59.9% to 54.5%. Additionally, the refractive index and extinction coefficient of LaF3 films with different oxygen content are obtained by fitting the transmittance test data. The results show that the refractive index and extinction coefficient of the films in 8–12 μm increase with the increase in oxygen content, the average refractive index increases from 1.339 to 1.478, and the extinction coefficient increases from 0.001 to 0.030. In this paper, the influence of oxygen impurity in the LaF3 film on its infrared optical properties is revealed, which lays a theoretical foundation for the development of high-performance LaF3 infrared antireflective film.

Optically and Mechanically Engineered Anti‐Reflective Film for Highly Efficient Rigid and Flexible Perovskite Solar Cells

AbstractSticker‐type anti‐reflective (AR) film is a powerful route to achieve the highest efficiency and commercialization of perovskite solar cells (PSCs) by improving the light transition efficiency (LTE). However, conventionally used AR film has high flexural rigidity owing to its limitation of material and thickness, thereby hindering its application to high‐efficiency flexible devices. This paper proposes a sticker‐type ultra‐thin perfluoropolyether (PFPE) AR film (SUPA) made of PFPE (n = 1.34) that is fabricated through a well‐designed two‐step peeling propagation method. The proposed SUPA demonstrates superior properties in terms of LTE (≈98.3%) and film thickness (≈20 µm), exhibiting the best performance among the existing AR films for PSCs. The SUPA‐assisted rigid and flexible PSC guarantees high short‐circuit current density (rigid ≈26.63 mA cm−2, flexible ≈23.05 mA cm−2) and power conversion efficiency (rigid ≈24.31%, flexible ≈20.05%). The SUPA sustains over 97.5% of its initial transmittance under exposure to the light (168 h) and damp heat condition (1000 h), and devices with SUPA show remarkable flexibility maintaining their initial efficiency after 10 000 cycles of a bending test (2 mm radius).

Microstructure and properties of La-doped Er2O3 anti-reflection films on CVD diamond

The composition and microstructure consisting of anti-reflection films was obtained by the power of magnetron sputtering. X-ray photoelectron spectroscopy (XPS) and High-resolution transmission electron microscopy (HRTEM) provided evidence to support that the doping La element exists as oxide in the grain boundaries of the matrix Er2O3 films. The undoped and La-doped Er2O3 films show a columnar crystal structure of the main cubic (222) plane. Twinning and a large number of dislocations show up in the undoped Er2O3 films due to the competitive growth of the columnar crystal. In addition, the La-doped Er2O3 films show a lower roughness (RMS) value in comparison with undoped Er2O3 films. The grain size of columnar crystals decreases significantly with increasing La concentration in the La-doped Er2O3 films. The fine grains resulted in the La-doped Er2O3 films developing high mechanical and impact resistance properties, with an increase in hardness from 12.6 ± 2.1 GPa to 26.1 ± 3.4 GPa and the eroding area rate decreasing from 38.9 % to 1.9 %. Moreover, the La-doped Er2O3 anti-reflection films on the chemical vapor deposition (CVD) diamond substrate maintained 74 % transmittance in the long-wavelength infrared range of 8–12 μm after sand eroding.

Enhancement of Light Extraction Efficiency of UVC-LED by SiO2 Antireflective Film

In order to achieve high quantum efficiency of AlGaN-based deep ultraviolet light-emitting diodes (UVC-LED), it is important to improve the light extraction efficiency (LEE). In this paper, theoretical simulation and experiment of SiO2 anti-reflective film deposited on UVC-LED were investigated. The effect of different SiO2 thickness on the light extraction efficiency of 275 nm UVC-LED was studied, showing that 140 nm SiO2 anti-reflective film can effectively improve the light output power of UVC-LED by more than 5.5%, which were also confirmed by the TFCALC simulation. The enhancement of UVC-LED light extraction efficiency by this antireflective film is mainly due to the 3λ2 light coherent effect at the SiO2/Al2O3 interface. Our work proved the promising application of antireflective coating on UVC-LED.

Bioinspired omnidirectional antireflective film with mechanical durability for efficient solar energy collection

•The internal structure of the dragonfly ommateum exhibits omnidirectional antireflection •Exquisite biomimetic structures could be prepared via a self-assembly strategy •Biomimetic antireflective film enables efficient omnidirectional antireflection •Biomimetic structure is the key to boosting the photovoltaic performance of solar cells Soaring developments in solar cells raise an urgent demand for superior antireflective (AR) materials to tackle the concern of their inadequate photovoltaic efficiency. Unfortunately, conventional AR films still suffer from a deficiency in omnidirectional antireflection and mechanical durability, significantly weakening their light-harvesting capability. Herein, a scalable biomimetic antireflective film (BARF) with ommateum-inspired multiscale hierarchical architecture was prepared using a method combining layer-by-layer thermal decomposition and in situ self-assembly. Remarkably, the BARF exhibited a transmittance of over 95% in light incident angles from −75° to 75°. Thereby, the output voltage of solar cells coated with BARF increased by 30.48% compared with commercial AR film. Furthermore, the BARF demonstrated excellent mechanical durability in falling-sand tests (∼2% transmittance loss). This work offers a general strategy for mass production of omnidirectional and durable AR films that are suitable for practical applications of protective AR film in solar cells, light pollution treatment, and video stealth technology. Soaring developments in solar cells raise an urgent demand for superior antireflective (AR) materials to tackle the concern of their inadequate photovoltaic efficiency. Unfortunately, conventional AR films still suffer from a deficiency in omnidirectional antireflection and mechanical durability, significantly weakening their light-harvesting capability. Herein, a scalable biomimetic antireflective film (BARF) with ommateum-inspired multiscale hierarchical architecture was prepared using a method combining layer-by-layer thermal decomposition and in situ self-assembly. Remarkably, the BARF exhibited a transmittance of over 95% in light incident angles from −75° to 75°. Thereby, the output voltage of solar cells coated with BARF increased by 30.48% compared with commercial AR film. Furthermore, the BARF demonstrated excellent mechanical durability in falling-sand tests (∼2% transmittance loss). This work offers a general strategy for mass production of omnidirectional and durable AR films that are suitable for practical applications of protective AR film in solar cells, light pollution treatment, and video stealth technology. Graphical Abstract View Large Image Figure Viewer Download Hi-res image

Дизайн и анализ просветляющего покрытия на поверхности кристаллического кремния солнечного элемента

With the positive development of photovoltaic technology, improving efficiency and reducing cost has become a global problem facing the solar industry. The development of solar cell anti-reflection film can significantly reduce the reflection of sunlight on the surface of the battery, increase the flux of light entering the battery, and create more photo-generated carriers, which is the most economical and effective way to improve the efficiency of the battery. More photo-generated carriers are produced, which is the most economical and effective way to improve the efficiency of batteries. Therefore, it’s of great value to explore a performance-matched antireflective film material for solar cells and its preparation process. The plasma enhanced chemical vapor deposition of silicon nitride antireflective coatings has been widely used in photovoltaic industry. The aim is to form an antireflection film on the surface of crystalline silicon solar cells and achieve good passivation effect. The thickness and refractive index of the antireflective film have an important influence on the performance of the battery. It is of great significance to explore the optimum technological conditions for preparing the optimum thin films. Considering the optical properties, stability, preparation process and production cost of antireflective film materials, the influence of antireflective film on the output characteristics of solar cells was studied by using PC1D simulation software.

ZINC SULFIDE ANTI-REFLECTIVE THIN FILM COATING FOR GERMANIUM OPTICAL WINDOWS

In this work, Anti-reflective thin film is made on Germanium (Ge) optical window, which is one of the most used materials in thermal imaging systems. ZnS material was used its optical transmittance between 2-14 m and due to the fact that it has a refractive index proportional to the refractive index of Ge. ZnS thin films have been prepared by Radio Frequency (RF) magnetron sputtering on Germanium (Ge) optical windows for anti-reflection coating (ARC). ZnS films were produced at different thicknesses using RF sputtering system working pressures under 3, 20 and 30 mTorr. The other RF systems parameters such as RF power, deposition temperature were kept constant for all depositions. Crystal structures, optical and surface properties of ZnS thin films were characterized with X-ray diffraction (XRD), Atomic force microscopy (AFM), Fourier transform ınfrared (FTIR) and UV-VIS transmission spectrometer. The characterization results of Ge optical windows coated ZnS thin films grown at 3 mTorr pressure show that high optical transmission and good crystallinity in ınfrared wavelength region (2-14 um).

The fabrication of anti-reflection grating structures film for solar cells using vibration-assisted UV nanoimprint lithography

To effectively improve the power conversion efficiency (PCE) of Si solar cells, vibration-assisted UV nanoimprint lithography based on piezoelectric driving is proposed to fabricate grating on Si solar cells. By applying piezoelectric vibration under the photoresist layer, vibration causes micro-displacement and micro-impact force, increasing the contact area between the photoresist and the grating's side wall and reducing surface tension. Meanwhile, the photoresist filling rate is increased by 25%. The effect of grating parameters on reflection is determined using Finite Difference Time Domain (FDTD), and grating with the best optical performance is optimized. In addition, the rationality of vibration introduction is verified by establishing a motion model, the influence of frequency and amplitude on the filling rate is analyzed using the finite element method, and a reasonable range of vibration parameters required by the experiment is obtained. Vibration-assisted UV nanoimprint is used to fabricate the periodic grating structures. PCE is increased by 25% when compared to bare Si solar cells. PCE of grating fabricated by vibration-assisted UV nanoimprint is increased by 4% when compared to traditional nanoimprint. The results show that vibration-assisted nanoimprint can efficiently and accurately fabricate periodic grating structures, resulting in improved Si solar cells performance.

Facile Solution Process of VO2 Film with Mesh Morphology for Enhanced Thermochromic Performance.

The fabrication and applications of VO2 film continue to be of considerable interest due to their good thermochromic performance for smart windows. However, low visible transmittance (Tlum) and solar modulation efficiency (∆Tsol) impede the application of VO2 film, and they are difficult to improve simultaneously. Here, a facile zinc solution process was employed to control the surface structure of dense VO2 film and the processed VO2 film showed enhanced visible transmittance and solar modulation efficiency, which were increased by 7.5% and 9.5%, respectively, compared with unprocessed VO2 film. This process facilitated the growth of layered basic zinc acetate (LBZA) nanosheets to form mesh morphology on the surface of VO2 film, where LBZA nanosheets enhance the visible transmittance as an anti-reflection film. The mesh morphology also strengthened the solar modulation efficiency with small caves between nanosheets by multiplying the times of reflection. By increasing the zinc concentration from 0.05 mol/L to 0.20 mol/L, there were more LBZA nanosheets on the surface of the VO2 film, leading to an increase in the solar/near-infrared modulation efficiency. Therefore, this work revealed the relationship between the solution process, surface structure, and optical properties, and thus can provide a new method to prepare VO2 composite film with desirable performance for applications in smart windows.

Antireflective film of porous silica.

We aimed to strengthen the antireflection coating of low refractive index, by using spinodal porous films based on phase separation of sodium borosilicate glass. Coating films were prepared by printing a glass paste onto a silica substrate, and melting at temperatures from 900°C to 1000°C, allowing phase separation at 600°C and finally etching to porosities of ∼60%. Coating with reflections as low as 0.5% was achieved, which consisted of a homogeneous porous layer of several micrometers in thickness and a graded region of up to 400 nm in width at the interface with the substrate. As to the optical property, simulations based on three-layer and two-layer models were carried out, into which was incorporated a term expressing mutual coherence degree between reflections from the surface and interface with coherence length of the light source.