Light Wavelength Region Research Articles

Effect of micro-crystallization on near-infrared shielding performance of Li0.09K0.23WO3 doped glass for energy-saving window

Effect of micro-crystallization (based on annealing time and temperature) on near-infrared (NIR)-shielding properties of Li0.09K0.23WO3 doped glass was investigated. The tungsten bronze doped glass was prepared by a facile melt-quenching technique. Structure and optical properties of the glass and glass-ceramics were characterized by X-ray diffraction analysis (XRD), Raman, and UV–Vis–NIR spectrophotometry, respectively. Increasing the annealing temperature increases in the range from 400 °C to 500 °C, the tungsten-functional unit Li0.09K0.23WO3 structure, which is responsible for NIR-shielding, changes the structural state from amorphous state to crystalline state gradually. Thus, the NIR-shielding properties of glass are significantly enhanced. Furthermore, annealing glass samples at 450 °C, during timeframe from 2 h to 8 h, causes crystallization and grain growth of the functional units, thus NIR-shielding property of the glasses is enhancing. It worth to be mentioned, that the increase of annealing temperature and time duration causes excessive grain growth in the glass matrix, which leads to decreasing of the optical transmittance in the visible light wavelength region. We have found, that the glass sample annealing temperature is at 450 °C with treatment time of 6 h yields the best results. In such manner the optical transmittance at λ = 1500 nm wavelength is 16.5 % and the highest transmittance of visible light wavelength region reaches 65 %. We conclude, that the NIR-shielding properties are adjustable and can be tailored by annealing temperature and time duration, which is expected to enhance the design and vary visual aspects of energy-saving windows.

Magnetization Study of Iron Sand from Sabang, Indonesia: The Potential of Magnetic Materials in the Photocatalytic Field

The magnetization of iron sand from Anoi Itam beach, Sabang, Indonesia, was investigated through sample testing and synthesis using the co-precipitation method. The purpose of this study is to analyze the magnetic properties of iron sand and review its potential in photocatalytic processes. Before being synthesized, the natural iron sand was separated and milled. The iron sand was dissolved in 37% v/v HCl, stirred, and heated for 30 min. This solution was filtered and precipitated with 6.5 M NH4OH while stirring and heating for 30 min. The magnetite formed was washed repeatedly with distilled water until it reached a normal pH, and then dried. Magnetite characterization tests were performed using XRF, XRD, VSM, and UV-Vis spectroscopy. The test results showed that the iron sand had a high magnetic quality with a concentration of 91.17% after the synthesis process. The resulting magnetite phase structure had a spinal inverse cubic shape, with the highest peak at the Miller index (311). From the VSM test, it is known that the resulting magnetite exists in a soft magnetic form with superparamagnetic groups. From optical absorption, magnetite has a gap energy of approximately 2.8 eV. It can be concluded that the magnetite from Anoi Itam Sabang has potential as a photocatalytic absorbent in the visible light wavelength region. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

High optical spin-filtering in antiferromagnetic stanene nanoribbons induced by band bending and uniaxial strain

Non-equilibrium spin-polarized transport properties of antiferromagnetic stanene nanoribbons are theoretically studied under the combining effect of a normal electric field and linearly polarized irradiation based on the tight-binding model at room temperature. Due to the existence of spin-orbit coupling in stanene lattice, applying normal electric field leads to splitting of band degeneracy of spin-resolved energy levels in conduction and valence bands. Furthermore, unequivalent absorption of the polarized photons at two valleys which is attributed to an antiferromagnetic exchange field results in unequal spin-polarized photocurrent for spin-up and spin-down components. Interestingly, in the presence of band bending which has been induced by edge potentials, an allowable quantum efficiency occurs over a wider wavelength region of the incident light. It is especially important that the variation of an exchange magnetic field generates spin semi-conducting behavior in the bended band structure. Moreover, it is shown that optical spin-filtering effect is obtained under the simultaneous effect of uniaxial strain and narrow edge potential.

Modeling of Optimized Lattice Mismatch by Carbon-Dioxide Laser Annealing on (In, Ga) Co-Doped ZnO Multi-Deposition Thin Films Introducing Designed Bottom Layers

In this study, modeling of optimized lattice mismatch by carbon-dioxide annealing on (In, Ga) co-doped ZnO multi-deposition thin films was investigated with crystallography and optical analysis. (In, Ga) co-doped ZnO multi-deposition thin films with various types of bottom layers were fabricated on sapphire substrates by solution synthesis, the spin coating process, and carbon-dioxide laser irradiation with post annealing. (In, Ga) co-doped ZnO multi-deposition thin films with Ga-doped ZnO as the bottom layer showed the lowest mismatch ratio between the substrate and the bottom layer of the film. The carbon-dioxide laser annealing process can improve electrical properties by reducing lattice mismatch. After applying the carbon-dioxide laser annealing process to the (In, Ga) co-doped ZnO multi-deposition thin films with Ga-doped ZnO as the bottom layer, an optimized sheet resistance of 34.5 kΩ/sq and a high transparency rate of nearly 90% in the visible light wavelength region were obtained.

Rational Distributed Bragg Reflector Design for Improving Performance of Flip-Chip Micro-LEDs

The distributed Bragg reflector (DBR) has been widely used in flip-chip micro light-emitting diodes (micro-LEDs) because of its high reflectivity. However, the conventional double-stack DBR has a strong angular dependence and a narrow reflective bandwidth. Here, we propose a wide reflected angle Ti3O5/SiO2 DBR (WRA-DBR) for AlGaInP-based red and GaN-based green/blue flip-chip micro-LEDs (RGB flip-chip micro-LEDs) to overcome the drawbacks of the double-stack DBR. The WRA-DBR consisting of six sub-DBRs has high reflectivity within the visible light wavelength region at an incident angle of light ranging from 0° to 60°. Furthermore, the influence of the WRA-DBR and double-stack DBR on performances of RGB flip-chip micro-LEDs is numerically investigated based on the finite-difference time-domain method. Owing to higher reflectivity and less angular dependence of the WRA-DBR, the RGB flip-chip micro-LEDs with the WRA-DBR have a stronger electric field intensity in the top side in comparison with RGB flip-chip micro-LEDs with the double-stack DBR, which indicates that more photons can be extracted from micro-LEDs with the WRA-DBR.

Photocatalytic Carbon Dioxide Conversion by Structurally and Materially Modified Titanium Dioxide Nanostructures.

TiO2 has aroused considerable attentions as a promising photocatalytic material for decades due to its superior material properties in several fields such as energy and environment. However, the main dilemmas are its wide bandgap (3–3.2 eV), that restricts the light absorption in limited light wavelength region, and the comparatively high charge carrier recombination rate of TiO2, is a hurdle for efficient photocatalytic CO2 conversion. To tackle these problems, lots of researches have been implemented relating to structural and material modification to improve their material, optical, and electrical properties for more efficient photocatalytic CO2 conversion. Recent studies illustrate that crystal facet engineering could broaden the performance of the photocatalysts. As same as for nanostructures which have advantages such as improved light absorption, high surface area, directional charge transport, and efficient charge separation. Moreover, strategies such as doping, junction formation, and hydrogenation have resulted in a promoted photocatalytic performance. Such strategies can markedly change the electronic structure that lies behind the enhancement of the solar spectrum harnessing. In this review, we summarize the works that have been carried out for the enhancement of photocatalytic CO2 conversion by material and structural modification of TiO2 and TiO2-based photocatalytic system. Moreover, we discuss several strategies for synthesis and design of TiO2 photocatalysts for efficient CO2 conversion by nanostructure, structure design of photocatalysts, and material modification.

Computer‐Aided Design of Fluorinated Flavin Derivatives by Modulation of Intersystem Crossing and Fluorescence

AbstractThis study aims at finding fluorinated flavin derivatives with modified intersystem crossing (ISC) and fluorescence properties. In total, photophysical properties of 8 derivatives were investigated computationally using combined density functional theory and multireference configuration interaction methods. On top of a screening procedure, the excited‐state decay mechanisms of selected chromophores were investigated in detail. Kinetic schemes including fluorescence, ISC as well as internal conversion (IC) channels were set up to unravel the complex excited‐state decay kinetics. We find two chromophores that exhibit promising properties with respect to fluorescence microscopy. Distinctive stabilization of the brightππ* state results in absorption in the green wavelength region and emission of (infra‐)red light. The1(πHπL)⤳3(πH–1πL) ISC channel of the flavin chromophore was found to be deactivated upon both modifications, but nonradiative deactivation of the fluorescence by IC appears to be a problem. Alternative modifications of the pteridine dione moiety were found to result in a marked stabilization ofnπ* states along with activation of El‐Sayed allowed ISC channels. For the latter two compounds, we predict fluorescence to be quenched by ISC followed by efficient population of the long‐livedstate via IC.

Enhanced performance of GaN-based visible flip-chip mini-LEDs with highly reflective full-angle distributed Bragg reflectors

High-efficiency GaN-based visible flip-chip miniaturized-light emitting diodes (FC mini-LEDs) are desirable for developing white LED-backlit liquid crystal displays. Here, we propose a full-angle Ti3O5/SiO2 distributed Bragg reflector (DBR) for blue and green FC mini-LEDs to enhance the device performance. The proposed full-angle Ti3O5/SiO2 DBR is composed of different single-DBR stacks optimized for central wavelength in blue, green, and red light wavelength regions, resulting in wider reflective bandwidth and less angular dependence. Furthermore, we demonstrate two types of GaN-based FC mini-LEDs with indium-tin oxide (ITO)/DBR and Ag/TiW p-type ohmic contacts. Experimental results exhibit that the reflectivity of full-angle DBR is higher than that of Ag/TiW in the light wavelength range of 420 to 580 nm as the incident angle of light increases from 0° to 60°. As a result, the light output powers (LOPs) of blue and green FC mini-LEDs with ITO/DBR are enhanced by 7.7% and 7.3% in comparison to blue and green FC mini-LEDs with Ag/TiW under an injection current of 10 mA. In addition, compared with FC mini-LED with Ag/TiW, light intensity of FC mini-LED with ITO/DBR is improved in side direction, which is beneficial to mix light in backlight system of liquid crystal displays (LCDs).

Electrical and Optical Characteristics of WOx, ZrHfO, and Tri-Layer WOx Embedded ZrHfO High-k Based SSI-LEDs

The solid state incandescent light emission device (SSI-LED), which can emit the broadband warm white light, is made from the high-k MOS capacitor after the dielectric breakdown [1-4]. Electrical properties of the capacitor, such as interface defect density (Dit ), oxide trapped charge density (Qot ), equivalent oxide thickness (EOT), and leakage current density (Jleakage ) are important to the dielectric breakdown process and eventually the optical properties of the emitted light. Since the zirconium hafnium oxide (ZrHfO) high-k material has superb gate dielectric properties, e.g., high crystallization temperature, low interface state density, oxide trapped charges, and high effective k value, it has been used as the gate dielectric layer of the MOS capacitor [5,6]. On the other hand, the WOx dielectric-based MOS capacitor and SSI-LED has been studied. The latter emitted light with relative high intensity due to the high emissivity coefficient of the W component [7]. However, the capacitor has a high leakage current which can be a reliability concern. In this paper, three types of MOS capacitors, i.e., with gate dielectrics made of ZrHfO, WOx, and ZrHfO/WOx/ZrHfO/WOx/ ZrHfO/WOx/ZrHfO, separately, have been fabricated into SSI-LEDs and studied for electrical and optical properties.MOS capacitors were prepared on a DHF pre-cleaned p-type <100> silicon (1015 cm-3) wafer. For the ZrHfO capacitor, the gate dielectric layer was sputter-deposited from the Zr/Hf (12/88 wt%) target in Ar/O2 (100:100 sccm) at 5 mTorr and 60 W for 12 min. The WOx layer was sputter-deposited from the W target (99.999 %) in Ar/O2 (40:100 sccm) at 5 mTorr and 60 W for 12 min. For the WOx embedded capacitor, the ZrHfO (2 min)/WOx (2 min)/ZrHfO (2 min)/WOx (2 min)/ ZrHfO (2 min)/WOx (2 min)/ZrHfO (2 min) stack was deposited in one pump down under the same conditions as each individual layer. The post-deposition annealing (PDA) was conducted at 900 ̊C under the O2 atmosphere for 5 min in furnace. An 80 nm thick ITO was sputter deposited and wet etched into round gate electrodes using an aqua regia solution. Then, the backside of the wafer was deposited with an aluminum thin film and annealed at 400 ̊C under H2/N2 (10/90) for 5 min. The dielectric breakdown voltage of the capacitor was determined from the current density-gate voltage (J-V) curve. The light emission characteristics the SSI-LED were measured from an optical emission spectrometer (OES, StellarNet).Electrical characteristics of the capacitors before and after the dielectric breakdown were discussed with respect to the gate dielectric material properties. Figure 1 shows the emission spectra of the 3 SSI-LEDs. They all emit broad band light in the range of UV to near IR. They are similar to the visible wavelength region of the solar light. The peak lengths λpeak’s of the ZrHfO, WOx, and WOx embedded devices are 638 nm, 687.15 nm, and 663 nm, respectively. The WOx SSI-LED has the highest emission intensity. It was reported that the emissivities of the pure (99.99 %) tungsten and the hafnium-3 wt% zirconium materials were 0.434 [8] and 0.30 [9] at 2000 K, respectively. Therefore, the inclusion of W component in conductive path may increase the light emission intensity of SSI-LED. According to the emission spectra, the CIE chromaticity chart has been prepared. The color correlation temperatures (CCT’s) and color rendering indices (CRI’s) were calculated. Y. Kuo, ECS Trans., 69, 23-29 (2015).C.-C. Lin and Y. Kuo, ECS J. Solid State Sci. Technol., 3, Q182 (2014).C.-C. Lin and Y. Kuo, J. Vac. Sci. Technol. B, 32, 011208 (2014).Y. Kuo and C.-C. Lin, Appl. Phys. Lett., 102, 031117 (2013).T.-C. Chang, F.-Y. Jian, S.-C. Chen and Y.-T. Tsai, Materials today, 14, 608-615 (2011).G. E. Moore, Cramming more components onto integrated circuits, McGraw-Hill New York, NY, USA (1965).M. Lorenz, H. von Wenckstern and M. Grundmann, Adv. Mater., 23, 5383-5386 (2011).R. D. Larrabee, JOSA, 49, 619-625 (1959).P.-F. Paradis, T. Ishikawa and S. Yoda, Int. J. Thermophys., 24, 239-258 (2003). Figure 1

Characteristics and Photovoltaic Applications of Au-Doped ZnO-Sm Nanoparticle Films.

Au-doped ZnO–samarium nitrate (Sm) nanoparticles with fixed concentrations of Sm (1 wt %) and various concentrations of Au (0.0, 0.5, 1.0 and 1.5 wt %) were prepared and used as photoelectrodes to enhance the photovoltaic efficiency of dye-sensitized solar cells (DSSCs). The cell fabricated with 1.5 wt % of Au-doped ZnO–Sm nanoparticles film achieved an optimal efficiency of 4.35%, which is about 76% higher than that of 0.0 wt % of Au-doped ZnO–Sm-based cell (2.47%). This increase might be due to the formation of a blocking layer at the ZnO–Sm/Au interface, which inhibits the recombination of electrons. This increase may also be attributed to the addition of rare-earth ions in ZnO to enhance the non-absorbable wavelength region of light via up/down-conversion of near-infrared and ultraviolet radiations to visible emission and reduce the recombination loss of electron in the cell. The efficiency of cells may be increased by the blocking layer and up/down-conversion process and thus promote the overall performance of the cells. This work indicates that Au-doped ZnO–Sm nanoparticle films have the potential to increase the performance of DSSCs.

Series Photothermoelectric Coupling Between Two Composite Materials for a Freely Attachable Broadband Imaging Sheet

As flexible wearable sensors and imagers are receiving attention from diverse social sectors, the freely attachable photothermoelectric (PTE) conversion technique should be evaluated to develop a highly usable safety sensor network. Although carbon nanotube (CNT)‐related materials should be effective, the key parameters/structures that maximize PTE conversion have not been clarified, thus hindering optimum device design and practical use. Herein, the flexible, sensitive broadband photodetection operation based on a coupling configuration between the CNT film photo/heat/electron channel and metal electrode is evaluated. Experimental PTE measurements and steady‐state thermal distribution simulations reveal that a series coupling of a p‐type CNT film channel and a highly negative Seebeck coefficient counter metal electrode facilitate superior photodetection performances than those of a parallel coupling configuration. Furthermore, subsequent device designs provide sensitive broadband photodetection from the millimeter‐wave to visible light wavelength regions with a minimum noise equivalent power of 5 pWHz−1/2 in an uncooled nonvacuum condition. Simultaneously, the mechanical flexibility of the proposed photodetector allows for its use in freely attachable sheet imager applications on curvilinear objects, and the nondestructive 3D photomonitoring of a defective intricately bent sample is demonstrated.

Investigation on the steered adsorption of aspirin through a constructed electronic transport tunnel by incorporating Ti into graphene with DFT approach

Focused on the decontamination of pharmaceutical pollutants via an adsorption approach, the adsorptive mode and capacity of adsorbents have been explored with a strategy by incorporating Ti into graphene (TG) frame using the density functional theory (DFT). Aspirin is used as a model molecule and pristine graphene (PG) as comparative substrate in this study. It is notified for PG, aspirin is adsorbed with a C-ring parallel orientation. It presents a weak physical adsorption through π-π interaction with an energy value of −0.846 eV. Whereas, a stronger chemical adsorption of aspirin on surface of TG with even lager adsorption energy of −2.772 eV is confirmed. The analysis based on Hirshfeld population and electronic distribution show the electrons of aspirin transfer to TG with an electron transport channel of O-Ti-C, which contribute to steer the enhanced adsorption. Furthermore, band structure and density of state display more densely and successive semimetal feature with a very slight band gap for TG, confirming the enhanced harvesting ability for wide wavelength regions of solar light. Consequently, the present investigation demonstrates by incorporating metal into PG frame, a strong adsorption material toward pharmaceutical contaminant could be achieved.

Automated Identification of Mineral Types and Grain Size Using Hyperspectral Imaging and Deep Learning for Mineral Processing

In mining operations, an ore is separated into its constituents through mineral processing methods, such as flotation. Identifying the type of minerals contained in the ore in advance aids greatly in performing faster and more efficient mineral processing. The human eye can recognize visual information in three wavelength regions: red, green, and blue. With hyperspectral imaging, high resolution spectral data that contains information from the visible light wavelength region to the near infrared region can be obtained. Using deep learning, the features of the hyperspectral data can be extracted and learned, and the spectral pattern that is unique to each mineral can be identified and analyzed. In this paper, we propose an automatic mineral identification system that can identify mineral types before the mineral processing stage by combining hyperspectral imaging and deep learning. By using this technique, it is possible to quickly identify the types of minerals contained in rocks using a non-destructive method. As a result of experimentation, the identification accuracy of the minerals that underwent deep learning on the red, green, and blue (RGB) image of the mineral was approximately 30%, while the result of the hyperspectral data analysis using deep learning identified the mineral species with a high accuracy of over 90%.

New Thermal Radical Inhibitors Based on a Triazene Metal Complex for Radical Polymerization.

New triazene based metal complexes such as Cu[1-(phenyldiazenyl)piperidine]2Br₂ (BTACHCuBr₂), Cu[1-(phenyldiazenyl)piperidine]2Cl₂ (BTACH-CuCl₂), Ni[1-(phenyldiazenyl)piperidine]2Cl₂ (BTACH-NiCl₂ · 6H₂O), Cu[2,2,6,6-tetramethyl-1-(phenyldiazenyl)piperidine]2Cl₂ (BTACM-SnCl₂), Ti[2,2,6,6-tetramethyl-1-(phenyldiazenyl)piperidine]2Cl₂ (BTACM-TiCl₂) were synthesized. All of the five compounds did not absorb in the visible light wavelength region and it does not have the color change disadvantage when using as an additive in polymerization. All materials also had thermal stability up to 245 °C. Among the synthesized compounds, BTACH-CuBr₂ showed the best radical inhibitor property when n-hexyl acrylate monomer was polymerized with the synthesized metal complexes at 150 °C isothermal condition. It exhibited more than 5 times of the polymerization delayed initiation compared to other synthesized metal complexes cases.

Tuning of electronic properties of novel donor–acceptor polymers containing oligothiophenes with electron-withdrawing ester groups

To investigate the substituent effects introduced into oligothiophene units, a series of novel donor–acceptor conjugated polymers containing ester-substituted oligothiophenes were synthesized by the direct C–H arylation polycondensation of bis(ester-substituted thienyl)benzothiadiazole and dibromo-substituted oligothiophenes. The ultraviolet–visible absorption spectra of three polymers showed two absorption bands in the visible light wavelength region, ascribed to π–π* transition and the intramolecular charge transfer bands. The oxidation potentials of the polymers exhibited a negative shift with an increase in the chain length of the oligothiophene units. By comparing these polymers with alkyl-substituted analogues, it was found that the introduction of electron-withdrawing ester groups induced a negative shift in the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels and affected the LUMO rather than the HOMO energy levels. As a preliminary experiment, organic photovoltaic cells using these polymers were prepared, and their photoelectric conversion characteristics were investigated in relation to their chemical structures.

Synthesis and characterization of the leaf-like Cu2O/CuO mixed phase nanosheets array

In this study, a leaf-like [Formula: see text] mixed phase nanosheets array was successfully prepared by anodization. XRD, EDS, and XPS analysis confirmed the formation of [Formula: see text] mixed phase nanostructures. SEM images indicate that the fabricated [Formula: see text] mixed phase nanosheets almost grow vertically on the substrate. The average height of nanosheets is approximately 500 nm. The optical absorption of the mixed phase covers the entire wavelength region of visible light and a little part of the near-infrared region of short wavelength.

Narrow Band-Edge Photoluminescence of Ga3+-Doped AgInS2 Quantum Dots

Quantum dots (QDs) composed of multinary I-III-VI semiconductors and related materials exhibit unique composition- and size-dependent physicochemical properties and have attracted much attention for the application to luminescent devices, solar cells, and photocatalyts because of their strong absorption coefficient and low toxicity. It has been reported that the QDs composed of CuInS2, AgInS2 and their solid solution with ZnS exhibited strong photoluminescence (PL) in the visible light wavelength region, PL peak wavelength being tunable by controlling the particle size and composition. Most of these multinary QDs exhibited broad defect-site PL peaks with a large Stokes shift, which may limit large-scale commercial applications. In contrast, recently, we have reported that rod-shaped (AgIn)xZn2(1-x)Te2 QDs with almost stoichiometric composition exhibited a clear exciton peak in the absorption spectra and a narrow band-edge emission peak in the near-IR wavelength region, the peak wavelengths of which were blue-shifted with a decrease in the x value.(1) In this study, we synthesize non-stoichiometric Ag-In-Ga-S (AIGS) QDs and then investigate their PL properties in relation to their chemical compositions.(2,3) AIGS QDs were synthesized in a mixture solvent of oleylamine and dodecanethiol by the thermal decomposition of the precursor mixture of elemental sulfur, Ag(OAc), Ga(acac)3, and In(acac)3 at 300 oC for 10 min with vigorous stirring under an N2 atmosphere, in which the ratios of Ag/(Ag+In+Ga) and In/(In+Ga) were varied. By adding methanol to the resulting solution, the target AIGS nanoparticles were isolated as wet precipitates. GaSx shell coating was carried out by the heat treatment of AIGS QDs in oleylamine in the presence of Ga(acac)3 and thiourea. Stoichiometric AIGS QDs, which had Ag/(Ag+In+Ga)= 0.5, exhibited a broad defect-site PL peak with a small narrow band-edge PL peak. With a decrease in the Ag/(Ag+In+Ga) ratio, the intensity of band-edge peak was enlarged, being optimal at non-stoichiometric composition of Ag/(Ag+In+Ga)= ca. 0.4. The wavelength of band-edge PL peak was blue-shifted from 610 to 500 nm by decreasing the content of In in AIGS QDs from In/(In+Ga)= 1.0 to 0.2. The GaSx coating of AIGS QDs produced amorphous shell layer of ca. 1 nm thickness on AIGS core surface. Thus-obtained AIGS@GaSx core-shell particles predominantly exhibited a band-edge PL peak of 41 nm in FWHM, and then the intensity of broad defect-site peak was significantly reduced to less than 15 %. The optimal PL quantum yield of AIGS@GaSx core-shell QDs was 28% with green band-edge emission at 530 nm. The observed wavelength tunability of the band-edge PL peak will facilitate possible use of these toxic element-free I-III-VI-based QDs in a wide area of applications. Reference (1) T. Kameyama et al., J. Mater. Chem. C 2018, 6, 2034. (2) T. Uematsu et al., NPG Asia Materials 2018, 10, 713 (3) T. Kameyama et al., ACS Appl. Mater. Interfaces 2018 , 10, 42844.

Reduction in connecting resistivity and optical reflection loss at intermediate layer for mechanically stacked multijunction solar cells

Reduction in the connecting resistivity and optical reflection loss at the intermediate region of mechanically stacked multijunction solar cells are discussed. The top and bottom substrates were bonded using an epoxy-type adhesive with dispersed transparent and conductive indium tin oxide (ITO) particles. The connecting resistivity of the intermediate layer was substantially decreased to 0.12 Ω cm2 for the stacked Si substrates with 40 nm surfaces roughened by SF6/Ar plasma irradiation. The optical reflectivity of the stacked GaAs and Si substrates was well decreased by the insertion of 130-nm-thick transparent and conductive indium gallium zinc oxide (IGZO) layers at the interfaces between the semiconductor substrates and the intermediate adhesive. The IGZO layers functioned as antireflection layers and provided high effective absorbance to the bottom Si substrates for light wavelength regions, in which the top GaAs substrate was transparent and the bottom Si substrate was opaque. The effective absorbencies at incident light angles between 0 and 50° ranged from 0.94 to 0.95 for the stacked GaAs and Si structure with IGZO layers, and from 0.80 to 0.82 for the structure without IGZO layers.

Optical photon transport and geometry contributions to time response of scintillation detectors

The sensitivities of both time and energy resolutions of a typical scintillation detector to major optical parameters (i.e. paint reflectivity, quantum efficiency of photomultiplier tube and attenuation coefficient) have been estimated using a dedicated Monte Carlo (MC) optical photon transport (OPT) simulation code, PHOTRACK, and the OPT capabilities of general-purpose code, FLUKA. Both cylindrical and parallelepiped geometries have been considered for the scintillator cell and lightguide. The results determine the scintillation light wavelength regions that the energy and time resolution represent enhanced sensitivities to small change/uncertainty in optical parameters.

Design of a Smartphone Platform Compact Optical System Operational Both in Visible and Near Infrared Spectral Regime

We report here the design of a low-cost and field portable smartphone-based compact optical system, which is suitable for applications in the visible (VIS)-near infrared (NIR) spectroscopic region. Using the universal serial bus-on the go protocol, the battery of the smartphone is used to power an external light-emitting diode, and its ambient light sensor (ALS) is used as a photo-detector. Using simple optical arrangements, a collimated light beam of a specific wavelength is allowed to pass through the sample solution, and the transmitted modulated light signal from the sample is received by the ALS of the smartphone. A custom built application “PhotoSense” has been developed, which configures the smartphone to measure intensity variation of the modulated signal into a readable form from the ALS sensor. Further using the same application, the field sensing data can be saved as a text file in the phone memory, and by using the communication facility, it can be shared anywhere in the world. The performance of the designed optical device has been evaluated for the VIS-NIR wavelength region of the incident light by measuring iron(II) and phosphate concentrations in water medium. The sensitivity of the device in measuring iron(II) and phosphate concentrations is found to be in terms of absorbance unit (AU) as 0.189 and 0.274 AU/(mg.L−1), respectively. The limit of detection of the proposed device is found to be 0.053 and 0.069 mg.L−1 for both the analytes.