Antireflection Research Articles

Aesthetic and efficient perovskite/Si tandem solar cells using luminescent down‐shifting textured anti‐reflection films

AbstractPerovskite‐based tandem cells are emerging as new photovoltaic (PV) cells with a high efficiency that exceeds the efficiency limit of single‐junction cells. Building‐integrated PVs that require high efficiency are attractive, but aesthetics play key roles in these urban applications. One of the most challenging problems with respect to aesthetic PV cells is the efficiency loss due to color tuning. Here, we demonstrate for the first time lossless full‐color tunable PV cells based on the use of textured luminescent down‐shifting (LDS) films with LDS dyes with ultraviolet‐selective absorption. The LDS anti‐reflection (AR) films improve the perovskite/Si tandem cell efficiency by reducing the loss of parasitic UV absorption of the layers above the perovskite film due to LDS effect and the loss due to cell reflection due to the textured surface. Therefore, color tuning with LDS AR films can be used to produce highly aesthetic and efficient PV cells for urban applications.image

Simulation study of TiO2 single layer anti-reflection coating for GaAs solar cell

Anti-reflection coating (ARC) plays an important role in reducing the reflection of incident light and absorbing more photons to produce more photoelectrons. In this paper, a single-layer TiO2 anti-reflection coating is performed on GaAs solar cells. In the simulation study, we compared the solar cell before and after ARC by using PC1D simulation software. The I–V characteristics, reflectance, and external quantum efficiency have been simulated with a refractive index of 2.324 at 600 nm wavelength. The simulated results show that the ARC-coated solar cell performs better. It is found that the power conversion efficiency of 24.75% reflection is 9.5%, and the EQE is 95% at the 62 nm thickness of the ARC layer. The optimized reflectivity was found to be around 5%, which is quite lower than that without ARC (32%).

Comparative Study of Polarization‐Dependent Conversion Efficiency of GaAs and Si Solar Cells at Oblique Incident Angles Using Surface DLAR Coating of MgF2/ZnSe

AbstractThe aim of this work is to minimize reflection losses in order to increase the efficiency of solar cells by using anti‐reflection coatings (ARCs). Despite extensive research on improving solar cell conversion efficiency at normal incidence, development at angle of incidence has received little attention. Thus, the reflectivity of single‐layer ARC (SLARC) MgF2 and ZnSe, double‐layer ARC (DLARC), MgF2/ZnSe on Si, and GaAs substrates at transverse electric (TE) and transverse magnetic (TM) modes of polarization in the visible and near‐IR regions for different angles of incidence is analyzed. The optical and electrical properties of Si and GaAs solar cells are analyzed by using the reflectance spectra of SLARC and DLARC at various angles of incidence for the TM and TE modes of polarization under the solar power spectrum (AM1.5). The achieved results due to the effect of DLARC are compared for Si and GaAs solar cells. From these analyses, it is concluded that MgF2/ZnSe is an appropriate DLARC for the range of wavelengths 400–800 nm at 10°–30° angles of incidence in TM mode for tuning the optical and electrical properties of Si and GaAs substrates for terrestrial applications.

Effect of Antireflection Coating on the Efficiency of an ITO/SnO2/CdS/CdTe Thin Film Solar Cell

Effect of Antireflection Coating on the Efficiency of an ITO/SnO2/CdS/CdTe Thin Film Solar Cell

High‐Throughput Computing Guided Low/High Index Optical Coupling Layer for Record‐Performance Semitransparent Organic Solar Cells

AbstractSemitransparent organic solar cells (ST‐OSCs) can be made in different colors, allowing light to pass through, and yet absorb enough visible and near‐infrared (NIR) light to generate electricity. However, it remains a challenge to achieve high performing ST‐OSCs over the two competing indexes of power conversion efficiency (PCE) and average visible transmittance (AVT). This work reports an effort to develop record‐performance ST‐OSCs using a low/high index optical coupling layer (OCL) and a 2D photonic‐structured antireflective (AR) coating. High‐throughput optical screening is used to improve the understanding of OCL structure−performance relationships and the predicting of NIR absorption enhancement for ST‐OSCs. The concurrent use of a low/high index Na3AlF6 (170 nm)/ZnS (110 nm) OCL, identified among about 200 thousand simulated device configurations and a 900 nm pitch‐sized 2D photonic‐structured AR coating, fabricated using nanoimprint lithography, enables the record‐performance ternary PM6:BTP‐eC9:L8‐BO‐based ST‐OSCs, achieving simultaneously a record‐high PCE of 15.2%, a high AVT of 32%, an impressive light utilization efficiency of 4.86%, and a favorable color‐rendering index of 82. The results of the ST‐OSCs demonstrated in this work provide an attractive option for a plethora of applications in self‐powered greenhouses and building‐integrated photovoltaic systems.

Design of core-shell SiO2 nanoparticles to create anti-reflection and anti-fouling coatings for solar cells

Amphiphobic coatings with the anti-reflective property offer a promising strategy to mitigate the degradation of photovoltaic conversion efficiency in solar cells caused by fouling and reflection of incident light. Despite advancements in developing transparent and liquid-repellent coatings, achieving integration of both properties still poses a significant challenge. In this work, a unique nanostructure coating with extremely low roughness and surface energy is constructed by integrating fluorinated cluster core-shell structured silicon sols (BASSF) into a self-made silicon precursor (SP) using a template-free two-step base/acid-catalyzed reaction. The exceptional anti-fouling performance of the S-P@BASSF coating is a result of the chemical inertness of the polymer and the unique structure of the sol-gel particles. This innovative approach provides a potential solution for fabricating high-performance coatings and materials. The coating is capable of recovering to 97 % of its initial efficiency swiftly, even after severe dust contamination. The coating exhibits remarkable anti-reflective property due to the combination of sol particles with varying refractive indices. The coating also displays high weathering resistance, maintaining contact angles with water (≥105°) and diiodomethane (≥85°) even after prolonged exposure to UV lamps, high temperature and high humidity weather. The results obtained in this study show that nanocomposite coatings via the preparation of smooth, high refractive index and low reflectivity have great potential for outdoor applications such as energy harvesting and optical instruments under wet conditions.

Numerical assessment of optoelectrical properties of ZnSe–CdSe solar cell-based with ZnO antireflection coating layer

In this work, a numerical assessment of the optoelectrical properties of the ZnO–ZnSe–CdSe heterojunction for a thin and cost-effective solar cell was made by using the PC1D simulation software. The photovoltaic (PV) properties have been optimized by varying thicknesses of the absorber layer of the p-CdSe layer, the window layer of n-ZnSe, and the antireflection coating (ARC) layer of ZnO, a transparent conductive oxide with enhanced light trapping, and wide bandgap engineering. There is a positive conduction band offset (CBO) of ΔEc = 0.25 eV and a negative valence band offset (VBO) of ΔEv = 1.2 − 2.16 = − 0.96 eV. The positive CBO prevents the flow of electrons from the CdSe to the ZnSe layer. Further, the impact of doping concentration on the performance of solar cells has been analyzed. The simulation results reveal the increase in the efficiency of solar cells by adding an ARC. The rapid and sharp increase in the efficiency with the thickness of the window layer beyond 80 nm is interesting, unusual, and unconventional due to the combined effect of morphology and electronics on a macro-to-micro scale. The thin-film solar cell with the structure of ZnO/ZnSe/CdSe exhibited a high efficiency of 11.98% with short-circuit current (Isc) = 1.72 A, open-circuit voltage (Voc) = 0.81 V and fill factor (FF) = 90.8% at an optimized thickness of 2 μm absorber layer, 50 nm window layer, and 78 nm ARC layer. The EQE of solar cells has been observed at about 90% at a particular wavelength at 470 nm (visible light range). Around 12% of efficiency from such a thin-layered solar cell is highly applicable.

CMOS Image Sensor for Broad Spectral Range with >90% Quantum Efficiency.

Even though the recent progress made in complementary metal-oxide-semiconductor (CMOS) image sensors (CIS) has enabled numerous applications affecting our daily lives, the technology still relies on conventional methods such as antireflective coatings and ion-implanted back-surface field to reduce optical and electrical losses resulting in limited device performance. In this work, these methods are replaced with nanostructured surfaces and atomic layer deposited surface passivation. The results show that such surface nanoengineering applied to a commercial backside illuminated CIS significantly extends its spectral range and enhances its photosensitivity as demonstrated by >90% quantum efficiency in the 300-700nm wavelength range. The surface nanoengineering also reduces the dark current by a factor of three. While the photoresponse uniformity of the sensor is seen to be slightly better, possible scattering from the nanostructures can lead to increased optical crosstalk between the pixels. The results demonstrate the vast potential of surface nanoengineering in improving the performance of CIS for a wide range of applications.

Effect of Mie resonances in coatings consisting of dielectric particles on the light propagation in substrate surface layers

The principal advantage of antireflection coatings consisting of subwavelength dielectric particle arrays is their ability to change the propagation direction of incident electromagnetic radiation and direct it along substrate surface layers. We have studied coatings consisting of Ge disk lattices on a glass substrate coated with an ITO film. The addition of Ge disks reduces the reflection in the wavelength region of the dipole and quadrupole resonances excited in the disks, compared to the ITO film reflection alone. Ge disk lattices also provide a much stronger absorption, compared to a Ge coating of the same thickness as the height of the disks. The presence of a peak in the absorption spectra and its dependence on the lattice period indicates that scattered radiation participates in the collective lattice resonance and is directed along the substrate surface. Such property of dielectric particle coatings can increase the efficiency of photoelectric devices, such as solar cells and photodetectors.

Diving deep into the milky way using anti-reflection coatings for astronomical CCDs

Diving deep into the milky way using anti-reflection coatings for astronomical CCDs

Preparation of chitin nanofibers through esterification and partial deacetylation followed ultrasonic treatment and their application for antireflective coating

Chitin nanofibers (ChNFs) are emerging as a very attractive material due to their biocompatibility, renewability, and excellent mechanical properties. ChNFs have broad applications in various fields. In this paper, ChNFs were prepared from commercially available chitin power through a dual modification of esterification with maleic anhydride followed partial deacetylation and subsequent ultrasonic treatment. Meanwhile, potential application of the ChNFs in antireflective coatings was explored. It was found that, as the deacetylation reaction time increased, the ChNFs became finer and more uniform. The ChNFs were positively charged under acidic conditions and negatively charged under basic conditions. At pH of 3.5, the ChNFs were dispersed well in water and the ChNF suspension showed excellent stability. The ChNF coatings fabricated by casting the ChNF suspensions with pH of 3.5 on glass substrate possessed antireflective capacity and yielded a 3 % transmission gain in the wavelength range of 390–800 nm compared to the uncoated glass.

Low polarization-sensitive ultra-broadband anti-reflection coatings with improved reliability.

Broader spectra, lower reflectivity and higher reliability are the performance requirements for broadband antireflective (BBAR) films. In this work, a BBAR film structure was proposed, which maintains extremely low reflectivity, ultra-wide spectra, low polarization sensitivity and practical reliability. The BBAR film consists of a dense multilayer interference stack on the bottom and a nano-grass-like alumina (NGLA) layer with a gradient low refractive index distribution on the top. The film was deposited by atomic layer deposition, while the NGLA layer was formed by means of a hot water bath on Al2O3 layer. The top NGLA layer has extremely high porosity and ultra-low refractive index, along with extremely fragile structure. To surmount the fragility of NGLA layer, a sub-nano layer of SiO2 was grown by atomic layer deposition to solidify its structure and also to adjust the refractive index with different thicknesses of SiO2. Finally, in the wide wavelength range of 400-1100 nm, the average transmittance of the double-sided coated fused quartz reaches 99.2%. The absorption, light scattering, reliability and polarization characteristics of BBAR films were investigated. An optimized BBAR film with low polarization-sensitivity and improved reliability was realized, which should be potentially promising for application in optical systems.

Sol-gel prepared amorphous Ta2O5 thin film for application in high LIDT antireflection coating and UV photodetection

In this report, a sol–gel method has been developed using tantalum ethoxide to produce homogenous thin films of amorphous Ta2O5 for application in optical coating for high power laser as well as photodetection in the UV range. Morphology, stoichiometry, optical properties, short range atomic structure and valence band have been investigated at various annealing temperature up to 500 °C. A large valence band onset of 3.5 ± 0.20 eV has been measured for the film annealed at 500 °C, ensuring hole blockage through the film and electron selective transport. Extended X-ray absorption fine structure (EXAFS) study has revealed the Ta–O bond distance to be 1.85 Å for as-deposited film, which increased with annealing and approached the crystallographic value. The sol-gel prepared Ta2O5 film has been used as antireflection (AR) coating on silicon and fused silica (FS) substrates. 99.4% transmission with a LIDT of 20 J/cm2 @6 ns at 1064 nm is obtained for Ta2O5/SiO2 AR coatings on FS. Using these sol-gel films, Ta2O5/Si vertical heterojunction photodetectors have been fabricated, which exhibited a responsivity of 560 mA/W, external quantum efficiency of 213%, and specific detectivity ∼1 × 1012 Jones at −1 V bias voltage and 325 nm illumination wavelength.

Omnidirectional antireflective coatings prepared with chitin nanofibers via layer-by-layer self-assembly

Antireflective coatings play an important role in various optical devices. Herein, we developed omnidirectional antireflective coatings fabricated with charged chitin nanofibers (ChNFs) through layer-by-layer (LbL) self-assembly technology. The charged ChNFs were prepared from chitin with modifications of esterification (negatively charged) and esterification followed partial deacetylation (positively charged), respectively, through ultrasonic treatment. The effects of concentration of the ChNF suspensions and number of bilayers on thickness, refractive index and antireflective capacity of the ChNF coatings were investigated. Refractive index of the ChNF coatings can be manipulated by changing concentration of the ChNF suspensions. Thickness of the ChNF coatings depends on number of bilayers and concentration of the ChNF suspensions. The ChNF coating on a glass substrate with 5 bilayers fabricated using the suspensions with concentration 0.1% had a refractive index of 1.36 and yielded 4% gain in transmittance compared to the glass at the wavelength of 550 nm. This work demonstrates that charged ChNFs are promising building blocks to fabricate antireflective coatings on large size substrates with high efficiency and low cost through LbL self-assembly.

Photoelectric properties of monolayer NbS2 and NbSe2 under three types of strain: A first-principles study

Based on the first principles, the crystal structure, photoelectric properties, and structural stability of two transition metal dichalcogenides (TMDCs) under different strain treatments are systematically calculated. The properties of NbX2 under tensile and compressive strains are discussed for the first time. Recently, a single-layer 1T structure with X atoms surrounding the transition metal atoms was synthesized in experiments. The 1T multi-forms were octahedral coordination structures, and some of the systems showed excellent semiconductor properties and stability. The results show that NbS2 has an indirect band gap under different strains and tends to transition to semiconductors which can effectively improve the material activity. NbSe2 has more excellent properties in the optical field and can be used to manufacture infrared lenses, anti-reflection coatings, and UV reflectors. This study provides a new understanding of the unconventional structure of NbX2 and provides theoretical guidance for the work in the field of TMDCs.

Reciprocity relations for interference coatings

By analyzing the wave equations, the coincidence of the energy reflection and transmission coefficients for the s- and p-polarization waves is herein substantiated when they are incident on the interference coating from opposite directions. The coating can be characterized by an arbitrary spatial profile of the refractive index, the limiting condition is the absence of optical losses in it. Reciprocity relations are obtained for the energy reflection and transmission coefficients of natural light for a structure in the form of a plane-parallel dielectric plate with interference coatings on its opposite sides. It is shown that when a structure with an absorbing plate is illuminated in opposite directions, the energy reflection coefficients can differ, while the energy transmission coefficients always coincide. Reciprocity relations are applied to the calculation of broadband antireflective interference coatings consisting of alternate layers Nb2O5 and SiO2 deposited on a polycarbonate plate. As a result, their correctness is confirmed and it is shown that the optimized antireflection two-sided interference coating provides approximately a five times lower averaged energy reflection coefficient compared to the optimized one-sided coating.

Modeling and Simulation of Fe-Doped GaN PCSS in High-Power Microwave

In this article, the characteristics of linear GaN photoconductive semiconductor switch (PCSS) in high-power microwaves are investigated by Silvaco TCAD (Technology Computer-Aided Design). By comparison of optical absorption efficiency among three types of PCSS structures, the optimized Fe-doped GaN PCSS is designed in a side-illuminated, vertical structure with a spot size of 1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 8 mm. The photocurrent of side-illuminated GaN vertical PCSS (vPCSS) begins to saturate at 1.65 mJ with the increase of applied optical energy. The average saturated switch resistance and electron concentration of vPCSS under a bias voltage of 5–20 kV are almost 8.2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pmb\Omega $</tex-math> </inline-formula> and 3.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\text{14}}$</tex-math> </inline-formula> cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-\text{3}}$</tex-math> </inline-formula> , respectively. As the device is in a saturated photocurrent state, the peak photocurrent is a linear function of bias voltage. As the device is in an unsaturated photocurrent state, improving the light energy is more effective than the withstand voltage of the device to increase photocurrent. Due to the short carrier lifetime, the GaN vPCSS has the response capacity to a 50-ps pulsewidth laser. Based on side-illuminated GaN vPCSS at the bias field 200 kV/cm, a narrowband microwave with adjustable frequency (3.3–5 GHz) could be generated. The maximum output power reaches up to 1.3 kW. Effects of anti-reflective (AR) and reflective coatings on optical absorption are investigated. The photocurrent of vPCSS with both AR and reflective coatings increases by 77.2% as compared with normal vPCSS.

Antireflection Coatings Based on PEDOT:PSS Conductive Polymer Using d-Sorbitol Additives for Terahertz Spectroscopy and Imaging.

Optical antireflection has been employed for a variety of applications in terahertz spectroscopy and detectors. However, current methods encounter challenges in terms of cost, bandwidth, structural complexity, and performance. In this study, a low-cost, broadband, and easily processed THz antireflection coating scheme based on the model of impedance-matching effect is proposed, using a 6 wt % d-sorbitol-doped poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (s-PEDOT:PSS) film. By adjusting the thickness of the s-PEDOT:PSS film, these biocompatible conductive polymers enable a significant reduction of Fresnel reflection and operate over a broad bandwidth between 0.2 and 2.2 THz. Applying the antireflective coating to the surface of the sample substrate and electro-optic probe crystal in THz spectroscopy and near-field imaging shows that the spectral resolution is significantly improved, and the devices exhibit more excellent intended performance. The findings of this study could aid in improving the measurement capability of various THz time-domain spectroscopy and imaging system.

High-absorption optical stack for aluminum kinetic inductance detectors.

We present a high-absorption optical stack design for aluminum (Al) kinetic inductance detectors (KIDs). Aluminum can be easily processed in micro-fabrication and is the most conventional superconducting material for KIDs. However, it is challenging to achieve high absorption in the Al absorber because of its high reflection at optical wavelengths. By embedding the thin Al film between an anti-reflection (AR) coating layer and a dielectric-based distributed Bragg reflector, we show that close-to-unity absorption can be achieved around a single wavelength (e.g.,≈98.9% at 1518nm). The reflection and transmission measurements agree well with the calculation based on the transmission matrix model. We also show our preliminary results of absorption ≥70% in a broader wavelength range (≈230n m) with multilayer AR coatings. The absorber design in a lumped-element KID is discussed. Our work paves the way to high-efficiency photon-counting and energy-resolving Al-based KIDs in the optical to NIR range.

Impact of Texturisation and Anti-Reflective Coatings on Light Absorption Efficiency in Solar Panels

The global shift from non-renewable energy sources to clean energy systems has put the existing renewable infrastructure to test. Solar power, the most promising resource for future, faces the barrier of lower efficiency rates than the conventional sources of energy, and thus increasing efficiency of each step involved can ensure its reliability. This study aimed to address the light absorption efficiency of solar cells through experimentation on texturisation and Anti-Reflective Coatings through the online simulator ‘Wafer Ray Tracer’. For the experiment, 3 different materials (Silicon Dioxide, Titanium Oxide, and Silicon Nitride) with texturized and planar surface were used and ray tracing was performed. The results of the experiment showed that all the 3 materials had significantly higher efficiency rates than control (bare silicon wafer) and texturisation of the surface also reduced optical losses to a great extent. Moreover, Texturized Silicon Nitride and Titanium Oxide recorded mean light absorption efficiency close to 98%, compared to 63% of planar Silicon Wafer. Keywords: solar panels, light absorption, texturization, anti-reflective coating