Wavelength Range Of Visible Light Research Articles

The Influence of Laser Induced Consolidation on the Ablation Threshold of Nanoparticulate ITO-layers

Indium tin oxide (ITO) is one of the few materials, which combines optical transparency in the wavelength range of visible light and electrical conductivity. It offers a wide range of applications in the field of optoelectronic devices such as solar cells or displays. To the present day, ITO is commonly deposited in a vacuum environment. Deposition under vacuum atmosphere is a cost-intensive process and not compatible with modern manufacturing techniques, like roll-to-roll processing. To overcome this limitation we propose the generation of ITO layers by deposition of ITO nanoparticles under atmospheric conditions.For the generation of functional devices structured layers are required. The exact damage threshold of nanoparticulate ITO layers is essential to minimize influence of the structuring process on the substrate.In our measurements we used three different substrates, spin coated layers, annealed layers and consolidated layers.

Broadband triple-layer SiOx/SiOxNy/SiNx antireflective coatings in textured crystalline silicon solar cells

The purpose of this study is to reduce textured crystalline silicon (TCS) substrate surface-reflectivity over a wide spectral range (300–1100nm), to improve the step coverage of the textured structure, and to shift the minimal value of reflection from the unabsorbed region to the absorbed region. The TCS solar-cell interface between air and silicon was added to a SiOx/SiOxNy/SiNx triple-layer anti-reflective coatings (TLARCs) structure using the plasma-enhanced chemical vapor deposition (PECVD) growth method. This paper presents theoretical and practical discussions, as well as the experimental results of fabricating the films and devices. The average reflection of the SiOx/SiOxNy/SiNx TLARs reduced to 2.01% (300–1100nm). The minimal value of reflection was shifted from 1370nm (unabsorbed region) to 968nm (absorbed region). The SEM images show effective step coverage. In comparison to the untreated TCS solar cells, applying the experimental SiOx/SiOxNy/SiNx TLARCs to conventional TCS solar cells improved the short-circuit current density (Jsc) by 7.78%, and solar-cell efficiency by 10.95%. This study demonstrates that the SiOx/SiOxNy/SiNx TLARCs structure provides antireflective properties over a broad range of visible and near-infrared light wavelengths. An effective step coverage and minimal value of reflection from unabsorbed region shift to the absorbed region is demonstrated.

Ferroelectric liquid crystals with axially chiral 2,2′-spirobiindan-1,1′-dione cores

The axially chiral mesogens 5-alkoxy-5′-[(4-alkoxybenzoyl)oxy]-2,2′-spirobiindan-1,1′-dione (QL7-n) were synthesised as racemic mixtures and resolved as single enantiomers by preparative chiral phase HPLC. The shorter homologues (R)-QL7-8 and QL7-9 form enantiotropic N* and SmC* phases, whereas the longer homologues (R)-QL7-10 and QL7-12 form an enantiotropic SmC* phase only. Texture analysis showed that the helical pitch of the N* phase is below the wavelength range of visible light; a helical pitch of 187 nm was measured at T – TNI = –5 K by selective reflection using enantiomerically enriched mixtures of (R)- and (S)-QL7-8 (0.35 ≤ ee ≤ 0.80). Spontaneous polarisations were measured as a function of temperature in the SmC* phase by the triangular wave method. PS values at saturation range from 102 nC cm–2 for (R)-QL7-8 to 120 nC cm−2 for (R)-QL7-9, which are up to three times greater than the highest polarisation previously reported for an axially chiral SmC* mesogen. Optical tilt angles θ were measured as a function of temperature and showed a sharp rise consistent with first-order N*–SmC* or I–SmC* transitions, with values at saturation ranging from 42 to 44°.

Effects of indium concentration on the efficiency of amorphous In–Zn–O/SiOx/n-Si hetero-junction solar cells

Semiconductor–insulator–semiconductor (SIS) hetero-junction solar cells comprising of the amorphous indium zinc oxide (a-IZO) layer directly deposited onto the n-type Si substrates by pulsed laser deposition were fabricated. Characterizations on the physical properties of the a-IZO layer and the a-IZO/SiOx interface as a function of In/(Zn+In) ratio were carried out to delineate their influences on the photovoltaic performance of SIS solar cells. The optical and electrical analyses indicated that the resistivity of a-IZO films decreased with increasing In concentration, reaching 4.5×10−4Ω-cm for In/(Zn+In)=0.5, which also exhibited a transmittance higher than 80% in the visible-light wavelength range. Moreover, combining with an optimally controlled insulating SiOx layer (about 2.0nm), the device exhibited excellent SIS solar cell performance with open-circuit voltage of 0.38V, short-circuit current density of 45.1mAcm−2, fill factor of 49.7% and a conversion efficiency of 8.4% under the AM1.5 illumination condition. The dramatic performance enhancement was attributed to the reduction of effective interface trap densities at the a-IZO/SiOx interface and the increase of carrier mobility in the a-IZO layer resulted from the increase of In/(In+Zn) ratio.

Magnéli phase Ti4O7 powder from carbothermal reduction method: formation, conductivity and optical properties

Magneli phase Ti4O7 was prepared by carbothermal reduction of TiO2 in vacuum. The products synthesized in different carbon black content and heated temperature were investigated by X-ray diffraction, scanning electron microscopy, and ultraviolet–visible (UV–Vis) spectra of products were tested also. The results show that the pure Ti4O7 powder is obtained with carbon black content of 4 wt% at 1,025 °C for 2 h in vacuum, their average particle size and BET surface area are about 6.10 μm and 4.107 m2 g−1, respectively. The resistivity of the samples is up to 0.11 Ω cm, and UV–Vis spectra shows the optical absorption bands cover the full range of visible-light wave lengths and extend into near-infrared region.

Dust attenuation in galaxies up to redshift ≃ 2

We want to study dust attenuation at ultraviolet (UV) wavelengths at high redshift, where the UV is redshifted to the observed visible light wavelength range. In particular, we search for a bump at 2175 A. We use photometric data in the Chandra Deep Field South (CDFS), obtained in intermediate and broad band filters by the MUSYC project, to sample the UV rest-frame of 751 galaxies with 0.95 < z < 2.2. When available, infrared (IR) Herschel/PACS* data from the GOODS-Herschel project, coupled with Spitzer/MIPS measurements, are used to estimate the dust emission and to constrain dust attenuation. The spectral energy distribution of each source is fit using the CIGALE code†. The average attenuation curve found for our sample galaxies exhibits a UV bump whose amplitude is similar to that observed in the extinction curve of the LMC super-shell region. The slope of the average attenuation curve at UV wavelength is found steeper than that for local starburst galaxies. The amount of dust attenuation at UV wavelengths is found to increase with stellar mass and to decrease as UV luminosity increases.

High Temperature Annealing Amorphous Hydrogenated SiC Films for the Application as Window Layers in Si-Based Solar Cell

Amorphous hydrogenated silicon carbide (a-Si1-xCx:H) films were deposited by plasma enhanced chemical vapor deposition and subsequently annealed in N2 atmosphere at 1100 °C. The effects of high temperature annealing on the film’s optical and structural properties were systematically analyzed. It was noted that after high temperature annealing, amount of Si-C bonds increased significantly and SiC nanocrystalline was formed on the surface of the film, which resulted in an increasing refractive index in wavelength range of visible light, a decreasing absorbance index (wavelength&lt;433.5 nm) and an increasing optical bandgap of the film. The changes of the optical properties illustrated that the performance of Si-based solar cell with a-Si1-xCx:H window layer could be improved by high temperature annealing.

Wideband Visible Wavelength Range MEMS Fabry–Perot Tunable Filter With Highly Accurate Calibration System

A novel microelectromechanical systems (MEMS) Fabry-Perot tunable filter (FPTF) and calibration system for accurately controlling the wavelength of the transmission peak in the wide wavelength range of visible light are reported. The MEMS FPTF consists of a Fabry-Perot filter having Ag alloy mirrors, an electrostatic actuator, and a capacitive gap sensor. The calibration system consists of the capacitive gap sensor, a capacitance measurement circuit, and a voltage controller. Through introducing the calibration system to MEMS FPTF, wavelength accuracy of more than ±1 nm is achieved. This is the accuracy level required for high-accuracy spectrum measurement in the range from 400 to 700 nm.

Enhancing the visible light absorbance of Bi2Ti2O7 through Fe-substitution and its effects on photocatalytic hydrogen evolution

The visible light-driven, photo-assisted hydrogen generation using a pyrochlore-type photocatalyst (A2B2O7), containing an earth-abundant element for boosting photoactivity, is presented. A wet chemical approach has been used for the synthesis of the pyrochlore photocatalyst. The characterization of the material using surface and optical techniques indicates that Fe can be successfully incorporated into Bi2Ti2O7 (BTO) with varying concentrations. The photocatalytic activity of the material was examined by performing hydrogen generation from a methanol–water mixture under UV–vis illumination in a slurry reactor. The wavelength range of visible light absorbed is improved by 100–200nm depending on Fe doping, and a corresponding increase in photocatalytic activity is noted. Replacing 1mol% of the Bi with Fe in the BTO (referred to below as 1% Fe doped or 1% Fe-BTO) is noted to be optimal in improving photocatalytic hydrogen generation, with more heavily doped samples showing progressively lower improvement.

Molecularly imprinted photonic hydrogels for fast screening of atropine in biological samples with high sensitivity

Based on molecularly imprinted photonic hydrogels (MIPHs) that combined the colloidal-crystal with molecular imprinting technique, a novel label-free colorimetric chemosensor for convenient and fast efficient detection of atropine with high sensitivity and specificity was developed. Due to the special inverse opal arrays with a thin polymer wall in which the imprinted nanocavities of atropine moleculars distributed, the proposed MIPHs designed as water-compatible exhibited high sensitive (as low as 1pg/mL), rapid responsive (less than 30s) and specific detection of atropine in complex matrix. The unique three-dimensional, highly-ordered photonic hydrogels would be obviously swelling in response to the specific atropine molecular recognition process and the response would be directly transferred into visually perceptible optical signal (change in color) that could be detected by the naked eye through Bragg diffractive shifts of ordered macroporous arrays. With a broad concentration range varying from 1pg/mL to 1μg/mL of atropine, the distinct color changes of MIPHs almost covered the whole visible-light wavelength range from blue to red for semi-quantitative analysis. The smart chemosensor was successfully employed to determine the trace level atropine in human urine samples, providing a fast and effective alternative for semi-quantitative detection of atropine for clinical analysis and forensic investigations.

Morphology and photoluminescence properties of YBO3:Eu3+(5%) tuned by B3+ source, stirring speed, pH value and post-annealing

YBO3:Eu3+ phosphors with different morphologies such as flower-like, spherical-like and cake-like have been hydrothermally synthesized without any additives by simply adjusting the B3+ sources, stirring speeds and initial solution pH values. During the hydrothermal reaction, stirring with suitable speed can reduce particle size and obtain more uniform size distribution. The emission intensity can be distinctly enhanced by stirring and post-annealing due to the micro-structural improvement and better crystallization. Interestingly, the weak acidity (pH=6) in the initial solution or post-annealing enhances the emission in the wavelength range of visible light, and weakens the emission around 700nm due to weakened distortion of the outside surroundings of Eu3+, which is useful in Plasma Display Panel (PDP) application.

Effects of Thermal Processing on Transparent Conducting Oxides TCO Used in Optoelectronic Devices

Due to its high electrical conductivity and high transparency in the visible light wavelength range, transparent conductive oxide thin films are able to be used as semiconductor materials on electronic devices. Among these films/materials, zinc oxides (ZnO), indium oxides (In2O3) and tin oxide thin films (SnO2) which are particularly attractive due to their optical, electrical and mechanical properties. In this investigation, the metal oxide films were prepared by pulsed laser deposition technique (PLD) using the same deposition parameters. The electrical, structural, and optical properties of these films were examined. The resistivity of the films were calculated based on the sheet resistance Rs measured by the standard four-point probe technique at room temperature. Concerning the structural properties, all films presented uniform, dense and smooth surface. The films were annealed for 1 hour at different temperatures (200-600 °C) in an argon atmosphere. Annealing greatly decreased the resistivity of the films. Atomic Force microscopy (AFM) measurements revealed an increase in surface roughness of the annealed films with temperature. Improvement to the crystallinity was observed from the double layers (SnO2)/(ZnO) annealed at 300-400 °C and above with a slight decrease in the optical transmittance. The transmittance of these films was measured in the spectrum range 200-2,000 nm using a spectrophotomer. High transmittance above (85%) in the visible region was exhibited by the films annealed at 400 °C and above. A lower resistivity and better spectra selectivity is a measurement of the quality and potential use of indium/tin oxides onto intrinsic zinc oxide deposited on cleaned glass substrates, for the application as transparent electrodes of electronic devices such as solar cells and organic light- emitting diodes.

The fabrication of SnSe/Ag nanoparticles on TiO2 nanotubes

SnSe and silver (Ag) nanoparticles were sequentially deposited on TiO2 nanotube (NT) by pulsed electrochemical deposition and polyol chemistry process, respectively. The morphological observation under scanning electron microscope (SEM) showed that the average size of SnSe was about 30 nm and the Ag was about 5 nm. Transmission electron microscopy (TEM) combined with selected area electron diffraction (SAED) examination indicated that Ag nanoparticles exhibited a well-defined crystallinity. However, SnSe nanoparticles were amorphous and they turned to crystalline after being annealed at 300 °C in the atmosphere. The photocatalytic behavior of SnSe/Ag-TiO2 NT was evaluated by UV–vis diffuse reflectance spectra (DRS). The results showed that the deposition of SnSe and Ag nanoparticles increased light absorption intensity in the wavelength range of visible light, which implied that the SnSe/Ag-TiO2 NT is a promising ternary hybrid material in photocatalysis.

An OLED Using Cellulose Paper as a Flexible Substrate

Cellulose paper was fabricated and employed as a substrate for flexible organic light-emitting diodes (OLEDs). The performance of the cellulose paper satisfies the criteria for a substrate of an OLED. The visible light transmittance of the cellulose paper was greater than 95% in the visible light wavelength range. After the OLED was fabricated on the cellulose paper substrate through a thermal evaporation method, the OLED exhibited a luminance of 620 cd/m2 at a driving voltage of 15 V and a current efficiency of 0.85 cd/A. This work suggests that cellulose paper is an environmentally promising substrate material for flexible OLEDs.

Optimization of Optical Properties of SiO&lt;sub&gt;2&lt;/sub&gt;/TiO&lt;sub&gt;2&lt;/sub&gt;/SiO&lt;sub&gt;2&lt;/sub&gt; Multilayer Films

The computer aid simulation of optical properties of thin films has been used to optimize SiO2/TiO2/SiO2 multilayer films to obtain high transparent films in this paper. The maximum transmittance at the visible light wavelength range is proper criteria for optical films optimizing design. The effect of design parameters (film thickness and refractive index) on optical properties of SiO2/TiO2/SiO2 multilayer films were also discussed in detail. According to the result of optimization, high quality SiO2/TiO2/SiO2 multilayer film with a maximum of &gt; 99% at visible light wavelength range can be achieved on the glass.

Photoinduced RNA Interference

Because RNA interference (RNAi) can be applied to any gene, this technique has been widely used for studying gene functions. In addition, many researchers are attempting to use RNAi technology in RNAi-based therapies. However, several challenging and controversial issues have arisen during the widespread application of RNAi including target gene specificity, target cell specificity, and spatiotemporal control of gene silencing. To address these issues, several groups have utilized photochemistry to control the RNA release, both spatially and temporally. In this Account, we focus on recent studies using photocleavable protecting groups, photosensitizers, Hand gold nanoparticles for photoinduced RNAi. In 2005 the first report of photoinduced RNAi used a caged short interfering RNA (siRNA), an siRNA carrying a photocleavable protecting group. Caging groups block the bioactivities of target molecules, but allow for complete recovery of these functions via photoactivation. However, some RNAi activity can occur in these caged siRNAs, so it will be necessary to decrease this "leakage" and raise the RNAi activity restored after irradiation. This technique also uses UV light around 350 nm, which is cytotoxic, but in the near future we expect that it will be possible to use visible and near-infrared light We also examine the application of photochemical internalization (PCI) to RNAi technology, which involves a combination of photosensitizers and light. Instead of inducing RNAi using light, the strategy behind this method was to enhance RNAi using RNA carriers. Many wellknown RNA carriers deliver siRNAs into cells by endocytosis. The siRNAs are trapped in endocytic vesicles and have to be released into the cytoplasm in order to express their activity. To achieve the endosomal escape of siRNAs, PCI technology employed photosensitizers to generate light-dependent reactive oxygen species (ROS) that disrupted the endocytic vesicles. In most studies, RNAi-mediated knockdown of the target gene was detected even without PCI. Recently, a polymer capable of trapping the siRNA in endocytic vesicles controlled RNAi almost entirely by light. CLIP-RNAi uses photosensitizing carrier proteins that can be activated over a wide range of visible light wavelengths. With this method RNA carrier/siRNA complexes are completely trapped within endosomes, and RNAi is controlled strictly by light. Such precise, light-dependent control will open up new possibilities for cellular and molecular biology and therapy. Most recently, gold nanoparticles (AuNPs) conjugated to siRNA have provided temporal and spatial control of RNAi. The light-dependent melting of AuNPs accompanied by a shape transformation induces the release of thiolated siRNAs from AuNPs. In this method, the unique optical properties of the AuNP enable deep penetration of the excitation light into tissues at nearinfrared wavelengths. The development of photoinduced RNAi technology will lead to novel insights into gene functions and selective drug delivery, and many other scientific fields will continue to influence its progress.

Wideband Visible Wavelength Range MEMS Fabry-Perot Tunable Filter with Ag Alloy Mirror

In this paper, we report the structure and the fabrication process of the new Micro-Electro-Mechanical Systems (MEMS) Fabry-Perot Tunable Filter (FPTF) device with Ag alloy mirror which is tunable in the wide wavelength range of visible light. The device has very simple structure, which consists of two substrates that are bonded by using novel bonding technology, polymer films, and inert gas plasma treatments. We confirmed that the wavelength of the 1st order transmission peak of fabricated device can be adjusted to a 400-700nm range by applying the different DC voltage. Our MEMS FPTF device successfully operates in the wide wavelength range of visible light, shows good agreement with simulation result.

液晶微胶囊制备宽波反射凝胶

Chiral nematic(N*) liquid crystal can reflect incident light selectively,and the reflective bandwidth is less than 150 nm commonly.Five N* liquid crystals were prepared from a nematic liquid crystal with negative dielectric anisotropy SLC10V513-200 and chiral compounds R1011,CB15.Their reflective spectra could cover with the entire visible spectrum.Polyurea microcapsules containing above N* liquid crystals were prepared by interfacial polymerization of isophorone diisocyanate(IPDI).By mixing same weight of five kinds of microcapsules together in surfactant OP-10 and IPDI,a gel was obtained.Applying an alternating electric field to an 80.0 μm gel film,the liquid crystal molecules in microcapsules would align parallel with the substrates.Curing monomer in the microcapsules with UV light and planar texture can be fixed,so the gel film which could reflect entire visible light wavelength range was prepared.

Enhancing the linear absorption and tuning the nonlinearity of TiO_2 nanowires through the incorporation of Ag nanoparticles

We report on the enhanced linear absorption and modified nonlinear absorption of TiO2 nanowires coated with Ag nanoparticles. Experimental results indicated that the coated Ag nanoparticles significantly increased the linear absorption of the nanostructures in the wavelength range of visible light. Z-scan experiments showed that when the excitation energy increased, the nonlinear absorption of the TiO2 nanowires changed from reverse-saturable absorption to saturable absorption. When Ag nanoparticles were coated on the TiO2 nanowires, the reverse-saturable absorption was significantly inhibited. The as-prepared nanostructures may find potential applications in the field of solar cells and all-optical switching.

Wafer-Scale Growth of ITO Nanorods by Radio Frequency Magnetron Sputtering Deposition

We demonstrate synthesis of tin-doped indium oxide (ITO) nanorods on 2-in. glass wafers via radio frequency (rf)-magnetron sputtering deposition. The nanorods possessed a single-crystal structure of bixbyite, grew along the <100> orientation of the cubic unit cell, and were vertically aligned to the substrates. Height and diameter of the nanorods were as large as ∼810 nm and 40–100 nm, respectively. The morphological, structural, compositional, optical, and electrical properties of the ITO nanorods were examined with respect to growth temperature (25–500°C) and growth time (10–60 min). ITO nanorod films synthesized at 500°C exhibited excellent electrical and optical property such as a low sheet resistance (∼41 Ω/□) and high transparency in the wavelength range of visible light (i.e., ∼87% transmission at 550 nm). The facile approach to synthesize ITO nanorods at a large scale demonstrated in this work may find various applications including the fabrication of high performance optoelectronic devices.