Reduction Of Light Reflection Research Articles

Optical characteristics of structures with silicon nanowires and metal nanoparticles


 
 
 To calculate the optical parameters, the finite difference method in the time domain (FDTD) was used, which can be applied to solve Maxwell’s equations. A large number of combinations of a planar structure with metal nanoparticles and a structure with nanowires and metal nanoparticles (NPs) were calculated. The height of nanowires h varied from 50 to 3000 nm, the period of the structure P was 100–600 nm, and the diameter of metal nanoparticles d was 50–400 nm. The reduction of light reflection was determined by the anti-reflection effect of the Si-NWs array itself and the direct scattering effect of metal nanoparticles. It was shown that all structures gave significantly lower reflection coefficients compared to that of a solid silicon plate.
 
 

Antireflection effect of high haze FTO for improving short circuit current density of perovskite solar cells

The optical properties of fluorine-doped tin oxide (FTO) coated glass substrates will limit the short circuit current density (Jsc), thus the power conversion efficiency (PCE) of perovskite solar cells (PSCs). This work compares the transmittance, reflectance, haze, and surface roughness of different FTO glass substrates. Then the performance of the PSCs, which were fabricated on these substrates, is discussed. The analysis indicates that higher haze FTO glass substrates with higher surface roughness are effective for the reduction of light reflection from NiOx-deposited FTO substrates/perovskite interfaces, leading to higher Jsc and thus the higher PCE of the PSCs. The antireflection effect is attributed to light absorption by the perovskite layer via multiple reflections due to the very rough FTO surface texture.

Surface texturisation for the reduction of light reflection in ZnO/Si heterojunction

ABSTRACT In this paper, the impact of pyramidal texture on a silicon substrate in ZnO/p-Si heterojunction was investigated. The texturisation of p-type silicon (100) substrate was obtained using the KOH anisotropic wet chemical etching method for different etching times. The RF magnetron sputtering technique was used to deposit ZnO thin films on textured Si substrates and planar Si substrates to form ZnO/Si heterojunction. The surface morphology was studied with field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). Optical properties were investigated using UV-Visible spectroscopy and photoluminescence (PL). The results show that the PL intensity in the visible region of the electromagnetic spectrum increases with the etching time, while a significant reduction is observed in the reflectance. Due to impressive anti-reflection response, ZnO/Si (textured silicon-TS) heterojunction can be effective in improving the efficiency of solar cells.

Texturization of diamond wire sawn multi-crystalline silicon wafers by micro-droplet etching

Diamond wire sawn multicrystalline silicon (DWS mc-Si) solar cell wafers have been known to be difficult to texturize by conventional acidic wet etching texturization process. A novel texturization method based on localized micro-droplet etching (MDE) has been developed, in which the micro-droplet is generated by controlled condensation of thermal vapor from a HF–HNO3–H2O bath. Uniformly distributed micron scale etch-pit type surface textures on DWS mc-Si wafers are made by the MDE process. Their light reflectivity is reduced to 18–21%, and their sawmarks are removed. Full size DWS mc-Si wafer samples were MDE textured, and send to a solar cell fabrication line along with the conventionally wet textured DWS mc-Si wafers as reference, without any adjustment of processing parameters for the MDE textured wafers. The average short circuit current of the MDE textured cells has been found to increase as compared to the reference cells, in a relative ratio approximately matching the final light reflection reduction ratio induced by the MDE textures. The average open circuit voltage and fill factor of the MDE textured cells are found to increase slightly, indicating that the MDE texture has not induced any significant increase in surface recombination of carriers, neither poorer contact of printed grid contact on cell surfaces. In average, 0.52% absolute increase of energy conversion efficiency is obtained.

Combination of surface texturing and nanostructure coating for reduction of light reflection in ZnO/Si heterojunction thin film solar cell

In this study, we report a single heterojunction solar cell based on n-type zinc oxide/p-type silicon. Three different solar cells were fabricated based on ZnO thin film on Si substrate, ZnO nanorods on Si substrate, and ZnO nanorods on micro-pyramidal structure of Si substrate. The comparison between these three kinds of solar cells was studied. Pyramidal structure of silicon was fabricated using chemical etching technique of p-type Si (100). The chemical solution consists of NaOH, isopropyl alcohol and hydrazine hydrate. The results showed that Si micro-pyramids can enhance optical absorption of Si substrates by increasing surface area and entrapping of incident light. For fabrication of uniform ZnO nanorods, a seed layer of ZnO was deposited on Si substrates via radio frequency magnetron sputtering technique. This layer can be used as an active n-type material in heterojunction solar cells as well. ZnO nanostructures can increase light absorption due to their high specific surface area. The combination of ZnO nanorods and Si micro-pyramids can enhance light trapping effect and increase the efficiency of solar cells. The structural and morphology of samples were studied using field-emission scanning electron microscopy, atomic force microscopy and X-ray diffractometry while the optical properties were investigated using photoluminescence and reflectance spectrometry. The efficiency and fill factor of solar cells were obtained from current–voltage characteristics using a solar simulator and a source-meter. The results showed that the efficiency of solar cell based on nanostructures of ZnO/micropyramids of Si is highly increased due to high anti-reflective behavior of this sample.

염료감응형 태양전지의 광전변환효율 향상을 위한 무반사 박막

DSSCs (dye-sensitized solar cells) based on <TEX>$TiO_2/SiO_2$</TEX> multi layer AR (anti-reflection) coating on the outer glass FTO (fluorine-doped tin oxide) substrate are investigated. We have coated an AR layer on the surface of a DSSCs device by using an IAD (ion beam-assisted deposition) system and investigated the effects of the AR layer by measuring photovoltaic performance. Compared to the pure FTO substrate, the multi layer AR coating increased the total transmittance from 67.4 to 72.9% at 530 nm of wavelength. The main enhancement of solar conversion efficiency is attributed to the reduction of light reflection at the FTO substrate surface. This leads to the increase of Jsc and the efficiency improvement of DSSCs.

Effective medium analysis of absorption enhancement in short-pitch metal grating incorporated organic solar cells.

The effective medium theory is applied to analyze the absorption enhancement in organic solar cells with a short-pitch metal grating. A 37% improvement in the absorption of the active layer is achieved with respect to that of a planar control cell. It is inspired that the propagating surface plasmon modes are excited at the interface between the effective medium layer and the flat metal plate, resulting in a reduction of light reflection. In real structure, the electric field redistributes with its intensity in the region with active materials infiltrated in the grooves increases significantly, exhibiting like hot spots to assist in achieving broadband absorption enhancement. Moreover, the localized surface plasmon resonances excited at the top of the metal ridges also contribute to the absorption enhancement in the cells.

Effect of ZnO Double Layer as Anti-Reflection Coating Layer in ZnO Dye-Sensitized Solar Cells

Dye-sensitized solar cells based on ZnO double layer anti-reflection coating (DLARC) thin films are investigated. The ZnO DLARCs were prepared by stacking two different ZnO morphologies prepared by two different techniques including rf-magneton sputtering (rf-ZnO) and sparking technique (sp-ZnO). The device using rf-ZnO as the bottom layer and sp-ZnO (3 cycles) as the top one exhibits short circuit current density (Jsc) of 5.80mA/cm2 and the maximum power conversion efficiency (PCE) of 1.88%, which is higher than that of the device stacking in reverse order and the device using ZnO single layer anti-reflection coating (SLARC). The main enhancement of PCE is attributed to the reduction of light reflection at the substrate surface. This leads to the increase of Jsc and the efficiency improvement of DSSCs.

Light absorption with branched gold cauliflower-like nanostructure arrays

In the present study, we have investigated the growth of branched gold (Au) cauliflower-shaped nanoparticles on Cicada's wing nanonipple arrays. The gas aggregation dc magnetron sputtering nanocluster source without size filtration was employed for fabrication of the samples. It was observed that the operating conditions of dc magnetron sputtering, such as gas pressure in the aggregation chamber and discharge power, control the deposition of charged clusters. By changing the operational conditions, a nanocauliflower-like (NCF) structure grew on the nanonipples. This Au nanostructure with a cauliflower-shaped surface feature was monitored using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The optical properties of these branched gold nanostructure arrays were also studied. Reduction of light reflection and the consequent light trapping suggest use of this branched structure for achieving broadband light absorption in Plasmonic solar cells as a result of plasmonic effects.

Preparation of nanostructure silica antireflective coatings by using sol–gel method

Sol–gel technology is a promising manufacturing method to produce antireflective silica thin films for solar energy applications. So to improve the properties of the films, controlling parameter of the sol–gel method is very important. In this study, soaking treatment effect on optical properties of silica antireflective thin films was investigated. UV–Visible Spectroscopy, Fourier-Transformed Infrared Spectrophotometer and Field Emission Scanning Electron Microscopy was used for the characterization of silica thin films. Results showed that all nanoporous silica layers cause to considerable reduction of light reflections compared with uncoated glasses. With single layer deposition, the amount of reduction depends on the dipping time of coating and has an optimal time. Also, it was found that solar transmittance increased from 91.5% for the bare slide up to 97.5% for the best made sample corresponding to two deposition cycles.

Suppressing light reflection from polycrystalline silicon thin films through surface texturing and silver nanostructures

This work demonstrates a novel method combining ion implantation and silver nanostructures for suppressing light reflection from polycrystalline silicon thin films. Samples were implanted with 20-keV hydrogen ions to a dose of 1017/cm2, and some of them received an additional argon ion implant to a dose of 5 × 1015 /cm2 at an energy between 30 and 300 keV. Compared to the case with a single H implant, the processing involved both H and Ar implants and post-implantation annealing has created a much higher degree of surface texturing, leading to a more dramatic reduction of light reflection from polycrystalline Si films over a broadband range between 300 and 1200 nm, e.g., optical reflection from the air/Si interface in the AM1.5 sunlight condition decreasing from ∼30% with an untextured surface to below 5% for a highly textured surface after post-implantation annealing at 1000 °C. Formation of Ag nanostructures on these ion beam processed surfaces further reduces light reflection, and surface texturing is expected to have the benefit of diminishing light absorption losses within large-size (&amp;gt;100 nm) Ag nanoparticles, yielding an increased light trapping efficiency within Si as opposed to the case with Ag nanostructures on a smooth surface. A discussion of the effects of surface textures and Ag nanoparticles on light trapping within Si thin films is also presented with the aid of computer simulations.

Laser stimulated light reflection reduction for silver nanoparticle-attached aluminum-doped zinc oxide substrate

A principal possibility to operate the light reflection within the 350nm–680nm spectra wavelength range and related extinction efficiency of silver nanoparticle-attached aluminum-doped zinc oxide substrate using an external laser light was shown. The treatment was performed by a nanosecond Nd:YAG (1064nm) and Er:glass (1540nm) lasers and by the corresponding bicolor regime. The principal role of the interfaces separating the ZnO:Al substrate and topology of Ag NP is established using AFM analysis of the Ag NP possessing 20nm, 40nm and 60nm average sizes. Different possible physical mechanisms are discussed including quadrupolar interaction of the electromagnetic wave and nanocomposites following the overlap between the surface plasmon resonance and the nano-trapping levels. The high selectivity to the photoexcited wavelength is explored. The sensitivity to the observed photoinducing laser wavelengths is discussed.

Reflectance reduction of InP wafers after high-temperature annealing

Broadband reduction of light reflection from the surface of InP wafers after high-temperature annealing in air has been observed. In the transparency region of the material, the reflection drop is accompanied by increasing transmission of light through the wafer. The spectral position of a deep minimum of the reflection coefficient can be tuned, by varying the temperature and the time of annealing, in a wide spectral range from ultraviolet to infrared. The effect is due to formation of thermal oxide layers on the surfaces of the wafer with optical parameters favorable for antireflection.

Reduction of light reflection at silicon-plate surfaces by means of subwavelength gratings in the terahertz region: errata

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text Shin-ichi Kuroo, Satoshi Oyama, Kazuo Shiraishi, Hiroyuki Sasho, and Kazushiro Fukushima, "Reduction of light reflection at silicon-plate surfaces by means of subwavelength gratings in the terahertz region: errata," Appl. Opt. 50, 2255-2255 (2011) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Reduction of light reflection at silicon-plate surfaces by means of subwavelength gratings in terahertz region

We investigate triangular surface-relief gratings for reducing reflection at a planar silicon surface for light in the terahertz frequency region of 0.3-3.0THz. Structural parameters of the one- and two-dimensional (1D 2D) subwavelength gratings required for the antireflection (AR) layer were obtained numerically. Experimental results for the AR effects agreed well with those obtained numerically, except for gratings fabricated with laser ablation, which causes structural fluctuations of the grating. In the 1D grating, a high transmittance exceeding 90% for the TM wave was obtained. 2D gratings comprised of arrayed micropyramids were experimentally confirmed to be polarization insensitive.

Hierarchically Structured Titania Films Prepared by Polymer/Colloidal Templating

Hierarchically structured titania films for application in hybrid solar cells are prepared by combining microsphere templating and sol-gel chemistry with an amphiphilic diblock copolymer as a structure-directing agent. The films have a functional structure on three size scales: (1) on the micrometer scale a holelike structure for reduction of light reflection, (2) on an intermediate scale macropores for surface roughening and improved infiltration of a hole transport material, and (3) on a nanometer scale a mesoporous structure for charge generation. Poly(dimethyl siloxane)-block-methyl methacrylate poly(ethylene oxide) (PDMS-b-MA(PEO)) is used as a structure-directing agent for the preparation of the mesopore structure, and poly(methyl methacrylate) (PMMA) microspheres act as a template for the micrometer-scale structure. The structure on all levels is modified by the method of polymer extraction as well as by the addition of PMMA particles to the sol-gel solution. Calcination results in structures with increased size and a higher degree of order than extraction with acetic acid. With addition of PMMA a microstructure is created and the size of the mesopores is reduced. Already moderate microstructuring results in a strong decrease in film reflectivity; a minimum reflectivity value of less than 0.1 is obtained by acetic acid treatment and subsequent calcination.

Stray-light problem in phase contrast microscopy or toward highly sensitive phase contrast devices: a review

In phase contrast microscopy there are various sources of unwanted stray light. Two that predominate in practice and are associated with the phase contrast technique itself occur when (1) the direct and the diffracted light cannot be completely separated by a phase plate (spatial filter) of a practically reasonable size and (2) the phase plate itself produces some light diffraction/scattering and reflections that diminish the sensitivity and imaging contrast of the phase contrast method. In the past, technological or engineering progress in conventional phase contrast instrumentation was mainly achieved by systematic reduction of stray light. An overview of this progress, supplemented by some unknown research results, is presented with an emphasis on the reduction of light reflections from the phase plate.