Antireflection Research Articles

Study of tantalum-based coatings magnetron sputtered on NiTi alloy in argon and argon/nitrogen atmosphere

In this work, surface morphology, corrosion resistance, and mechanical properties of tantalum sputtered NiTi in Ar and Ar–N2 atmospheres as well as room and 200 °C temperatures have been investigated. FESEM studies showed the positive effect of heat on forming a uniform and dense Ta layer under the Ar atmosphere whereas it left an adverse mark on coatings in the Ar–N2 atmosphere. XRD patterns depicted amorphous coatings in all samples meaning 200 °C was not sufficient for the formation of crystallized Ta. AFM 3D images of surface topographies suggested that smooth and compact layers were produced in the Ar-injected chamber while the coatings containing N in their chemical composition owned irregular ups and downs with a higher porosity degree. Electrochemical measurements indicated that despite nonuniformity, Ar–N2 coatings were more resistive whereas polarization resistance was at least three times greater than that of Ar coatings. Finally, nanoindentation results showed that the coating formed at 200 °C and Ar condition had the highest nano-hardness, Young's modulus, and elastic recovery. The sample coated in Ar–N2 condition and the same temperature, however, expressed the least mechanically-favorable character.

Influence of fitting algorithms on thickness determination during monitoring of optical coatings

The monitoring of thickness evolution during the deposition of optical interference coatings is widely performed by transmittance measurements and continuous comparison with theoretical models. The fitted thickness of the actual layer is influenced by the quality of the signal. Effects from light path, substrate and spectrometers result in deviations because these are often not part of the models. We show an implementation of these unmodeled effects in the fitting algorithms. The outcome of different configurations while coating the same optical filter design is compared. Additionally, the time consumption of these strategies is investigated to verify their suitability for production.

Experimental analysis of Anti-Reflective coating performance in desert Climate: Yield analysis, soiling impact and cleaning durability evaluation

The objective of this paper is to experimentally evaluate the performance of a commercial single layer inverse porous silica Anti-reflective coating (ARC) system when installed in desert locations. Three aspects were evaluated: the first aimed to assess the electrical performance by comparing the yield of a non-coated PV module with the AR-coated one. The second focused on analyzing the impact of soiling on the optical properties of ARC glass samples and comparing them to the uncoated ones. Lastly, a laboratory linear abrasion test was conducted to evaluate the durability of the investigated commercial ARC coating against long-term dry cleaning. In addition to the technical investigation, an economic analysis was conducted to better evaluate the feasibility of ARC integration under desert climates.The results indicate that the investigated ARC panels exhibit superior electrical performance, with a PR higher by relatively 2 % compared to the non-coated ones. Moreover, the ARC glass samples demonstrate good optical performance against soiling, with a Soiling Losses (SL) relatively lower by 3.7 % compared to non-coated samples for the same exposure period. Regarding the abrasion test, the investigated ARC coating exhibited relatively good durability, with a transmittance loss (Tloss) of only 2.6 % after 1500 brushing cycles. This is equivalent to 28.8 years of weekly cleaning from the initial state. The findings also demonstrate that the implementation of ARC panels can significantly benefit desert locations as they can enhance the power plant's production by 5 %, resulting in a 2.7 % drop in the LCOE compared to the uncoated modules.

Polarization beam combining by fused silica subwavelength grating

The fused silica subwavelength grating is applied to the combination of orthogonally polarized beams, of which wavelength tunability and robustness of geometric deviation is numerically investigated by combining efficiency based on the modal method. The experimental beam combining efficiencies of fabricated fused silica subwavelength gratings applied at 532 nm, 832 nm, and 1064 nm, respectively, are 82.9%, 80.3% and 86.6% for continuous-wave lasers without anti-reflection coatings. The experimental output combined from two 6J, 10ns, 1064 nm pulse lasers is 9.67J by fabricated 4-inch-wafer fused silica subwavelength grating with laser-induced damage threshold measured up to 26.4J/cm2. The polarization beam combining method by the subwavelength grating is applicable not only in the combination of diode laser arrays as pumping source but also in the power enhancement of bulky laser systems in fields such as laser cleaning, laser cutting and laser shock peening.

Superhydrophobic route of fabricating antireflective, self-cleaning, and durable coatings for solar cell applications

Superhydrophobic route of fabricating antireflective, self-cleaning, and durable coatings for solar cell applications

Optical enhancement in perovskite thin films using moth-eye anti-reflection film

Perovskite solar cells represent an emerging photovoltaic technology. With the latest record efficiencies exceeding 25% coupled with low fabrication cost and tunable transparency, perovskite solar cells demonstrate promising applications as solar windows. For these applications, the perovskite solar cells need to be semi-transparent to allow incident light to pass through the windows while generating electricity. However, semi-transparency compromises light absorption in the solar cells. In this work, optical enhancement in perovskite thin films using moth-eye anti-reflection (AR) film is investigated. Perovskite thin films with different thicknesses are used and the thickness is controlled by varying the spin speeds during the deposition of the perovskite precursor. The optical effects in the perovskite films without and with moth-eye AR film are studied. From the findings, the reflection loss is reduced by maximum of ∼4%, which contributes to a higher light absorption in the perovskite layer, due to the AR effect of the moth-eye structure. These results imply that the moth-eye film can be a promising and facile alternative for developing a highly efficient and semi-transparent perovskite solar cell with a thin absorber layer.

Fabrication of antireflective coatings with self-cleaning function using Si–Ti modified hollow silicon mixed sol

The antireflective coating (ARC) is fabricated by the sol-gel method using mixed sol modified by Si–Ti composite sol. The effects of the mixing ratio of Si–Ti composite sol and hollow silica sol on the surface morphology, optical properties, mechanical properties, and wetting ability of the ARC were studied. Moreover, the self-cleaning ability and environmental stability were examined via dip coating the modified sol on glass substrates. The proposed ARC exhibited a total solar-weighted transmittance (Тsw) of more than 94.97% over a wavelength range of 380–1100 nm, significantly higher than that of the bare glass substrate (Тsw = 90.62%). After modification, the proposed ARC exhibited a hardness of 3 H. In addition, the coating presented an extremely hydrophilic surface with a minimum water contact angle of less than 5°. Water droplets resulted in the formation of a water film on the ARC surface, which could significantly reduce the adverse effects of subsequent pollutants on the coating transmittance; simultaneously, owing to the introduction of TiO2, the coating could oxidatively decompose organic contamination. Finally, damp test results showed that the ARC transmittance only decreased by 0.05%, indicating good environmental stability.

Investigation of photocatalytic performance of single layer superhydrophilic film: TEOS/PF‐127

AbstractMultifunctional antireflective coatings (ARC) have great importance in various applications such as optical devices, flat panel displays, solar cell devices, and so on. Here in this work, highly transparent superhydrophilic film was developed on a cleaned glass substrate by depositing porous TEOS/PF‐127 using the spin coating technique. The coating shows a maximum transparency of 95% in the visible region (400–800 nm). The morphology and porous nature of the prepared sample was analyzed using FESEM and BET analysis respectively. The prepared film exhibited a water contact angle of 9° ensures its superhydrophilic nature. It is also noteworthy that TEOS/PF‐127 coating possesses photocatalytic activity by showing good photo degradation against MB (Methylene Blue) dye under UV‐B (280–315 nm, 50 W) and halogen (340–850 nm, 50 W) light irradiation. The present work provides a simple cost‐effective method to enhance the optical transparency of the glass substrate along with good self‐cleaning properties via photocatalytic activity.

Nb2O5 deposited by ion-assisted reactive magnetron sputtering for near-infrared optical coating: Power modulation and performance degradation

Nb2O5 exhibits outstanding optical properties within the near-infrared spectra, suggesting considerable potential for application in optical coatings. In this work, Nb2O5 was deposited by ion-assisted reactive magnetron sputtering. The potential of sputtering power modulated various properties of Nb2O5 was revealed. The results showed that the deposition rate rose up to 2.05 Å/s with increasing power. Optimal deposition of amorphous Nb2O5 was achieved at 450–600 W, exhibiting a defect-free surface and cross-section, accompanied by a minimal roughness of 0.36 nm and a consistent refractive index range of 2.10 to 2.35. These Nb2O5 demonstrated excellent optical performance in the near-infrared band. The reflectance of high-reflective coatings achieved 99.8 %, and the reflectance of antireflective coatings achieved 0.06 %. NbO2 was successfully deposited at 900 W, presenting a promising method for large-scale NbO2 deposition, independent of precise oxygen control. The high-temperature performance of Nb2O5 was evaluated, and the results showed significant crystallization at 750 °C, inducing a substantial rise in defects and surface roughness, exceeding 6 nm. The optical properties of Nb2O5 were affected, resulting in high-temperature performance degradation in optical coatings. Specifically, the reflection spectra of anti-reflective coatings experienced a 48 nm shift. The reflectance of high-reflective coatings decreased from 99.8 % to 41.2 %, and was accompanied by a blue shift exceeding 80 nm in the near-infrared band. The critical temperature of this dramatic change was identified to be within 450–550 °C. Typical catastrophic optical damage on the laser facet was observed. These findings provide valuable insights for the application of Nb2O5 optical coatings in near-infrared lasers.

Highly Facet-reflection Immune 53GBaud EML for 800G Artificial Intelligence Optical Transceivers

We developed a facet-reflection immune 53GBaud electro-absorption modulated laser (EML) for 800G artificial intelligence (AI) optical network. An ultra-low anti-reflection (AR) coating reflectivity of 2x10-5 has been demonstrated for straight waveguide. Based on Hakki-Paoli method, we characterized the ultra-low AR using the ripple test technique. Such ultra-low AR is critical in achieving excellent eye pattern and optical transmission for 800G AI supercomputing.

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.

Nanophotonic broadband infrared antireflection coatings based on dielectric Si3N4 nano-pillar arrays

Dielectric Si3N4 nano-pillar arrays (NPA) are designed for the broad infrared waveband antireflection applications. The Wood-Rayleigh anomaly diffraction and Mie-type scattering (M − S) resonance characteristics of the NPA nanophotonic structures are analyzed, which show the excellent optical performances. M − S resonance can be broadened by high-index semiconductor substrate and the interactions between nanopillars, which resulting the expected ultra-low light reflection at the broad infrared waveband. The orderly and uniformly large area Si3N4 NPAs are successfully fabricated by low-cost nanosphere lithography, and the measured infrared light reflection spectrums are fit well with the theoretical results. For the GaSb TPV cell with the emitter temperature of 1200 °C, the ultralow flux-spectrum-weighted reflection of ∼1.72 % is obtained with the fabricated Si3N4 NPA, which demonstrate great potential for infrared optoelectronic applications.

Experimental and theoretical studies on improving the efficiency of ZnO-based dye-sensitized solar cells using single-layer anti-reflective coating

The effect of a single-layer anti-reflective coating (ARC) on ZnO-based dye-sensitized solar cells (DSSCs) is theoretically predicted and verified by experimental fabrication. By the transfer matrix method (TMM), the absorption of the DSSC with and without the single-layer ARC is calculated and the improvement in short-circuit current density (∆ Jsc%) is estimated. The optimized thickness of the ARC required to obtain maximum improvement in the short-circuit current density (∆ Jsc%) is determined. By employing ARC with the calculated optimized thickness, the fabrication of spin-coated ZnO-based DSSCs is carried out. The structural and optical parameters are studied using XRD analysis and UV absorption spectra. The efficiency of the DSSC with and without the ARC is measured by intensity-modulated photocurrent and photovoltage spectroscopy. The theoretically predicted efficiency of the DSSC with and without ARC agrees well with the experimental values that provide insights about improving the electrical performance of the DSSC by the ARC.

High-quality ZnO anti-reflective coatings for CdSe crystal in the infrared wavelength

The anti-reflective coating of infrared window materials plays an important role in infrared devices. In this paper, pure ZnO nanoparticles dispersion liquid was obtained by purifying and redispersing ZnO nanoparticles of about 4 nm prepared by the sol-gel method. High-performance ZnO coatings were prepared on CdSe crystals by the dip-coating method. Changing the thickness of the ZnO coating can change the position of the optimal anti-reflection. In the wavelength range of 1280–3000 nm, the lowest reflectance can reach 0.20 %, and the average reflectance is reduced from 26.36 % to 6.02 %. In the wavelength range of 3000–5000 nm, the lowest reflectance can reach 0.22 %, and the average reflectance is reduced from 26.91 % to 2.23 %. In the wavelength range of 8000–10,000 nm, the lowest reflectance can reach 0.20 %, and the average reflectance is reduced from 28.24 % to 1.28 %. Especially in the wavelength ranges of 3000–5000 and 8000–10,000 nm, the anti-reflection is significant in the whole band. In addition, the coating has excellent high-temperature stability and mechanical properties. This work is of great significance for preparing infrared anti-reflection coatings by chemical method.

Antireflective coatings of chitin nanofibers on glass fabricated through electric field deposition

Due to their wide variety of practical applications, antireflective coatings have been studied intensively. In this paper, we developed a novel approach to fabricate antireflective coatings on glass substrate by using charged chitin nanofibers (ChNFs) and electric field deposition. The ChNFs were obtained via ultrasonic treatment of the modified chitin through partial deacetylation, esterification and esterification followed partial deacetylation (dual modification), respectively. The ChNF coatings prepared by applying electric field deposition and using aqueous dispersions of the dual modified ChNFs had antireflective capacity. The effects of electric field intensity, electric field application time and ChNF dispersion concentration on antireflective capacity of the ChNF coatings were studied. The coating obtained by applying 55 V electric field for 5 min and using the dispersion of the dual modified ChNFs with concentration of 0.05 wt% yielded increase in transmittance of a glass substrate (∼ 2.4% at wavelength of 550 nm). The results of this study demonstrate that electric field deposition is a high efficiency and low cost approach to prepare antireflective coatings on large size and nonplanar substrates with charged nanofibers.

Dye-Based Bifacial Silicon Solar Cell Fabrication

Abstract: Solar photovoltaic (PV) is a well-known energy harvesting technology or a semiconductor device that is used in generating electricity from the sunlight via the conversion process. Currently, solar photovoltaic is increasingly growing as an alternative renewable energy in conventional power generation. There are two types of solar photovoltaic cells which are monofacial and bifacial solar cells. The difference between these two solar cells is, monofacial, only generate electricity when the light touches the front side whereas the bifacial solar cell does generate electricity from both the front and rear side. In this research project, the bifacial solar cell is used to fulfil the purpose of increasing the power conversion efficiency as it can generate power from both surfaces. The bifacial is known to produce more energy up to 27 % than the monofacial according to the claims of some manufacturers. The base of this bifacial solar cell is silicon. Silicon purely contains an atomic structure that makes it suitable and more stable to be the raw material of a semiconductor due to its behaviour to block and conduct electricity. This is mainly due to silicon having the conductive properties of metal as well as an insulator. The silicon wafer will undergo the whole fabrication process to become the semiconductor devices. However, there is a problem encountered with the PV cell when it is consistently improving and when analysing the potential areas: on the power conversion efficiency. This is one of the challenges that can be solved with a strategy to increase the availability of the photon trapping of the solar cell which we called as the surface passivation of the bifacial solar cell. Surface passivation is a way that can minimise the recombination loss and efficiency loss while enhancing the optical path length of the solar cell on the photon absorption. It is the most significant step to increase the efficiency of the bifacial solar cell which is also known as an anti-reflection coating (ARC) using dye-based coating techniques. The development of the anti-reflection (ARC) lays on the fabrication techniques, optical performance and the light trapping structures as well as their impact on its efficiency

Synergistic effect on silicon surface under low energy he ion irradiation at elevated temperatures

One of the major challenges in nuclear fusion, nanolithography, and various industries is the effect of low energy ion irradiation on the surface morphology of materials. For example, the effect of low energy irradiation on plasma-facing materials' lifetime in fusion reactors, the effect on the optical systems in nanolithography laser produced plasma devices, and the effect on mass production of effective and flexible anti-reflecting coatings in photovoltaic (PV) industry. Silicon and carbides in particular, showed interest in nuclear fusion as potential wall materials, as in mirror designs for nanolithography devices, and as coatings in PV system components. Recently innovative novel Si nanostructures such as nanocones (NCs) demonstrated great feasibility in several areas including the next generation PV cells, batteries, supercapacitors, nano-optoelectronics, photonics, and energy storage devices. Their unique electronic properties and significantly higher absorption over a wide broadband range, offer paramount potential in various fields including microelectronics, optoelectronics, photonics, photovoltaics, biology, sensors, templet for selective growth (on nanostructured substrates), fast electronic devices, and even in high- density data storage. We tailor Si NCs using simultaneous low energy helium (He) ion irradiation on planar Si (111) and (100) and Ta metal masks. In a series of successive experiments, three key parameters, temperature, flux, and presence of Ta metal impurity, were tuned to study the progression of nanostructure development, as well as the effect of these nanostructures on key material properties. Before performing He ion sputtering experiments, 100 eV Ar+ ion irradiations, for 10 min duration, were also performed in-situ in each case for removing any preexisting SiO2 form planer Si substrates. Clear and distinctive progressions of NC development were found during the tuning of each parameter. During the temperature dependent studies, we clearly observed a sequential progression from thicker and less dense cones (773 K) to finer and more densely packed NCs (1073 K). On the other hand, during the case of flux dependent studies, it was found that increasing flux increases the size of the NCs, with low flux resulting in sparsely placed nanodots, and high fluxes resulting in large conglomerates. Finally, the effect of Ta impurity shows an increased propensity for NCs development. In addition, using optical-reflectivity studies we clearly observed a significant reduction (from ∼65 to almost zero) in optical reflectivity.

Enhancing Performance of Ultraviolet C Photodetectors Through Single-Domain Epitaxy of Monoclinic β-Ga2 O3 Films and Tailored Anti-Reflection Coating.

Implementing high-performance ultraviolet C photodetectors (UVC PDs) based on β-Ga2 O3 films is challenging owing to the anisotropic crystal symmetry between the epitaxial films and substrates. In this study, highly enhanced state-of-the-art photoelectrical performance is achieved using single-domain epitaxy of monoclinic β-Ga2 O3 films on a hexagonal sapphire substrate. Unlike 3D β-Ga2 O3 films with twin domains, 2D β-Ga2 O3 films exhibit a single domain with a smooth surface and low concentration of point defects, which enable efficient charge separation by suppressing boundary-induced recombination. Furthermore, a tailored anti-reflection coating (ARC) is adopted as a light-absorbing medium to improve charge generation. The tailored nanostructure, which features a gradient refractive index, not only substantially reduces the reflection, but also suppresses the surface leakage current as a passivation layer. This study provides fundamental insights into the single-domain epitaxy of β-Ga2 O3 films and the application of ARC for the development of high-performance UVC PDs.

Optimization of retinin expression and the application with wax emulsion in nanocoatings

Anti-reflective nanocoatings that mimic the eyes of fruit flies are biodegradable materials with great market potential for a variety of optical devices that require anti-reflective properties. Microbial expression of retinin provides a new idea for the preparation of nanocoatings under mild conditions compared to physicochemical methods. However, the current expression level of retinin, the key to anti-reflective coating, is low and difficult to meet mass production. In this study, we analyzed and screened the best expression hosts for Drosophila-derived retinin protein, and optimized its expression. Chinese hamster ovary (CHO) cells were identified as the efficient expression host of retinin, and purified retinin protein was obtained. At the same time, the preparation method of lanolin nanoemulsion was explored, and the best anti-reflective ability of the nano-coating was determined when the ratio of specific concentration of retinin protein and wax emulsion was 16:4, the pH of the nano-coating formation system was 7.0, and the temperature was 30 ℃. The enhanced antireflective ability and reduced production cost of artificial antireflective nanocoatings by determining the composition of nanocoatings and optimizing the concentration, pH and temperature of system components may facilitate future application of artificial green degradable antireflective coatings.

Organic Solar Cell with an Active Area > 1 cm2 Achieving 15.8% Certified Efficiency using Optimized VIS‐NIR Antireflection Coating

Organic solar cells are on the verge of reaching 20% power conversion efficiency (PCE) on small device areas (< 0.1 cm2). Herein, an improved efficiency of organic solar cells based on the donor polymer D18 combined with the non‐fullerene acceptor Y6 with an active area of ≥1 cm2 reaching a certified PCE of 15.8% is reported. This is achieved due to an increase in photogenerated current enabled by a fully magnetron sputtered multilayer antireflection coating (ARC) custom designed for the absorption profile of the photoactive layer. The influence of this ARC in the visible to near infrared range is quantified by means of full optical device simulations predicting a photogenerated current gain of 3.9%. With the advanced device architecture, the best solar cell is measured independently by Fraunhofer ISE calibration lab obtaining the following values: open‐circuit voltage = 851.3 mV, short‐circuit current density = 25.11 mA cm−2, fill factor = 73.89% on an active area of 1.0645 cm2 thus yielding the improved world record efficiency in the category of cell areas ≥1 cm2.