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Luminescent solar concentrators (LSCs) harness light generated by luminophores embedded in a light-trapping waveguide to concentrate onto smaller cells. LSCs can absorb both direct and diffuse sunlight, and thus can operate as flat plate receivers at a fixed tilt and with a conventional module form factor. However, current LSCs experience significant power loss through parasitic luminophore absorption and incomplete light trapping by the optical waveguide. Here, we introduce a tandem LSC device architecture that overcomes both of these limitations, consisting of a poly(lauryl methacrylate) polymer layer with embedded cadmium selenide core, cadmium sulfide shell (CdSe/CdS) quantum dot (QD) luminophores and an InGaP microcell array, which serves as high bandgap absorbers on the top of a conventional Si photovoltaic. We investigate the design space for a tandem LSC, using experimentally measured performance parameters for key components, including the InGaP microcell array, CdSe/CdS QDs, and spectrally selective waveguide filters. Using a Monte Carlo ray-tracing model, we compute the power conversion efficiency for a tandem LSC module with these components to be 29.4% under partially diffuse illumination conditions. These results indicate that a tandem LSC-on-Si architecture could significantly improve upon the efficiency of a conventional Si photovoltaic cell.

Organic light‐emitting transistors (OLET) evolved from the fusion of the switching functionality of field‐effect transistors (FET) with the light‐emitting characteristics of organic light‐emitting diode (OLED) that can simplify the active‐matrix pixel device architecture and hence offer a promising pathway for future flat panel and flexible display technology. This review systematically analyzes the key device/molecular engineering tactics that assist in improving the electrode edge narrow emission to wide‐area emission for display applications via three different topics, that is, narrow to wide‐area emission, vertical architecture, and impact of high‐κ dielectric on the device performance. Source–drain electrode engineering such as symmetric/asymmetric, planar/non‐planar arrangement, semitransparent nature, multilayer approach comprising charge transport, and work function modification layers enable widening the emission zone. Vertical OLET architecture offers short channel lengths with a high aperture ratio, pixel type area emission, and stable light‐emitting area. Transistors utilizing high‐κ dielectric materials have assisted in lowering the operating voltage, enhancing luminance and air stability. The promising development in achieving wide‐area emission provides a solid basis for constructing OLET research toward display applications; however, it relies on developing highly luminescent and fast charge transporting materials, suitable semitransparent source/drain electrodes, high‐κ ‐dielectrics, and device architectural engineering. [ABSTRACT FROM AUTHOR]

We developed a high spatial resolution and sensitive detector particularly suitable for radiation dose measurements in radiotherapy at small fields and X-ray imaging applications. The detector is based on a silica optical fiber whose sensitive terminal is functionalized by grafting Ag-doped ZnS scintillating materials that emit blue luminescence under X-ray irradiation. Due to the small scintillating head of the detector, the acquisition signal is quite low, and it is measured by a sensitive photon counter plugged at the other terminal of the fiber. The weaker signal can be enhanced significantly by adding a metal coating over the scintillator. Therefore, this study presents the effect of metal thickness and density on the signal amplification at high irradiation energies of 6 MeV and 15 MeV using a Linear Accelerator (LINAC). In addition, the stem effect was characterized for regular to small field beam size and shows that the detector is almost free from stem contribution during high energy irradiation. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenide (TMD) monolayers, with their direct band gaps, have attracted wide attention from the fields of photonics and optoelectronics. However, monolayer semiconducting TMDs generally suffer from low excitation absorption and emission efficiency, limiting their further applications. Here a flip‐over plasmonic structure comprised of silver nano‐disk arrays supporting a WS2 monolayer sandwiched by hexagonal boron nitride (h‐BN) layers is demonstrated. The flip‐over configuration optimizes the optical process with a free excitation/emission path from the top and a strong plasmonic interaction from the bottom. As a result, the photoluminescence from the TMD monolayers can be greatly enhanced more than tenfold by optimizing the metasurface, which can be further improved nearly tenfold by optimizing the thickness of bottom h‐BN. This study shows the advantages of using the flip‐over structure, where the plasmonic interaction between the metasurface and TMDs can be tuned by introducing optimized plasmonic arrays and h‐BN layers with suitable thickness. This hybrid device configuration paves a reliable platform to study the light–matter interaction, achieving highly efficient plasmonic TMD devices. [ABSTRACT FROM AUTHOR]

Transparent single Dy3+, Sm3+, and Dy3+/Sm3+ co-activated tungstate-tellurite (TWKZBi) glass matrices were synthesized via melt-quenching process. The optical features of the prepared glass matrices were examined with the aid of the absorption spectra. Under various excitation wavelengths (366, 388 and 454 nm), Dy3+ doped TWKZBi (TWKZBiDy) glasses revealed a prevailing emission peak ⁓575 nm related to the yellow band (4F 9/2 → 6H 13/2) transition, while Sm3+ doped TWKZBi (TWKZBiSm) glass matrices reveal strong intense emission peak at ∼600 nm associated with the orange-red band (4G 5/2 → 6H 7/2) transition. The emission intensity progressively surges with an increment in Sm3+ ion content (up to 1.5 mol%), confirming the ET mechanism between Dy3+ and Sm3+ ions. Application of Dexter's ET formulation with the Reisfeld's approximation revealed that the ET mechanism involves a non-radiative dipole-dipole (d-d) interaction between Dy3+ and Sm3+ ions. The average lifetime (τ a v g) values for the 4F 9/2 state of Dy3+ ions in the TWKZBiDySm glass sample was measured and found that these values decreased with increasing Sm3+ ion content. In addition, the ET efficiencies (η D y → S m) of the TWKZBiDySm glass matrices were evaluated using the lifetime curves. The color coordinates (x , y) and the correlated color temperature (CCT) values of the co-activated glass samples were estimated. Based on the chromaticity coordinates and CCT values, it was found that the desired color of the TWKZBiDySm glass samples can be modulated from warm white light to orange-red light via precisely adjusting the concentration of Sm3+ ions and at selected excitation wavelengths. Furthermore, the emission intensity observed at 373 K was 83.83 % compared to the emission intensity at ambient temperature, indicating the excellent thermal stability of the TWKZBiDySm glasses prepared. The above results confirm that the prepared Dy3+/Sm3+ co-activated TWKZBi glass matrix can be a promising candidate for white light and other photonic devices. Transparent single Dy3+, Sm3+, and Dy3+/Sm3+ co-activated tungstate-tellurite (TWKZBi) glass matrices were synthesized via the melt-quenching process. The PL spectra were studied at selected excitation wavelengths to examine the energy transfer process in the present Dy3+/Sm3+ co-activated TWKZBi glass via altering the concentration of Sm3+ ions. The emission profiles with varying temperatures from RT to 448 K indicate the good thermal stability of the prepared TWKZBiDySm glasses. Therefore, the prominent results confirm that the prepared TWKZBiDySm glasses will be beneficial for white light and other fascinating photonic applications. [Display omitted] • Dy3+/Sm3+ co-activated tungstate-tellurite (TWKZBiDySm) glasses synthesized. • Emitting color can be tuned from warm white to orange-red with dopant concentration. • Energy transfer from Dy3+ to Sm3+ ions confirmed via theoretical models. • TWKZBiDySm glasses exhibit excellent thermal stability with high activation energy. • Optimized glass could be a potential candidate for w-LEDs and photonic devices. [ABSTRACT FROM AUTHOR]

A new technique, which can increase the wireless light fidelity channel capacity based on the white light emitting diode, is proposed. It is implemented by using the non-orthogonal frequency shift keying and the sparse carrier sampling at the same time. The proposed method is verified by using the 1-meter wireless visible light communication link with the 30-MHz frequency response. The maximum power penalty due to the sparse carrier sampling is 6 dB at the compression ratio of 62.5 %. The bit error rate of $9.5\times 10^{-4}$ is measured at the frequency spacing of 0.1 MHz (1% of 10-MHz RF carrier). The wireless channel capacity of 130 Mb/s, which corresponds to 13 times of on-off keying-non-return to zero signal (10Mb/s), is obtained at the compression ratio of 70 % using the proposed technique. We also confirm that the 16-NoFSK signal with the 26-dB input signal to noise ratio can be recovered even at the compression ratio of 75 % when the received optical power is more than -6 dBm.

A $1\times 2$ multimode interferometer beam splitter based on mid-infrared emitting chalcogenides waveguides is designed. This device multiplexes mid-infrared light in two channels whose respective passbands overlap either CO2 or CO absorption bands, respectively between 4.20- $4.32~\mu \text{m}$ and 4.50- $4.86~\mu \text{m}$. The proposed device offers a low-cost solution for monolithic combination of broadband on-chip mid-infrared light emission with dispersive spectroscopic element devoted to mid-IR multigas sensing applications. Based on restrictive interference mechanism in a $1\times 2$ multimode interferometer, the multimode section dimensions (width and length) are engineered to increase the imbalance between the two ports for the two passbands and consequently to increase the output contrast ratio. Tolerances to variations from the optimum device design resulting from processing conditions (materials fabrication and sputtering, photolithography and dry etching steps) are assessed. In particular, the $1\times 2$ multimode interferometer diplexer spectral transmission is investigated as a function of deposited film refractive index and multimode section dimensions (width and length) deviation from designed values. Input and output ports tapering is introduced to reduce the device insertion loss. [ABSTRACT FROM AUTHOR]

The development of novel visible light photoinitiators (PIs) with low mobility for 3D printing will open up new applications for photopolymerization. In this work, a polymerizable visible light PI DCCA containing an oxime acryloyl ester structure was designed and synthesized. Its linear absorption has a maximum in the visible region (400–480 nm), overlapping well with the emission spectra of conventional blue light sources, and it can effectively induce acrylate polymerization under irradiation with a 450 nm LED lamp. In addition, migration of DCCA in the 3D printed samples is very low compared with DCCB, which has a similar structure but a phenyl moiety instead of the copolymerizable acrylate as the oxime ester group. The utility of DCCA in 3D printing was demonstrated by printing a 3D object with challenging geometric features with high resolution and accuracy. [ABSTRACT FROM AUTHOR]

Applied methods for detecting water impurities in organic solvents, such as Fischer titration, include wayward equipment and toxic reagents. This method is inapplicable for detecting H2O in D2O, but suitable techniques like NMR-, IR-, and mass-spectrometry are costly. We report a low-cost, novel luminescent sensor material based on terbium-europium 3D MOF compound developed for facile, portable, and disposable monitoring of water quantities. Our sensor is able to determine water traces in D2O and aprotic organic solvents. Treating the material to solvent leads to the change in intensities ratio of terbium and europium bands in emission spectra depending of water content and nature of solvent. For D2O calibrating plot $\text{I}_{\mathrm {Eu}}/\text{I}_{\mathrm {Tb}}$ –%H2O is linear whereas for dioxane and acetonitrile the dependence becomes linear in the coordinates $\text{I}_{\mathrm {Eu}}/\text{I}_{\mathrm {Tb}}$ -ln(%H2O). The results reveal the potential application of developed sensor for ratiometric quantitation of H2O admixtures in D2O, organic solvents, transformer oil, etc. [ABSTRACT FROM AUTHOR]

Abstract: ZnS, as one of the first semiconductors discovered and a rising material star, has embraced exciting breakthroughs in the past few years. To shed light on the design principles and engineering techniques of ZnS for improved/novel optoelectronic properties, the fundamental mechanisms and commonly employed strategies are proposed in this review. Recent progress on modifications of ZnS allows it to be extensively and effectively used in versatile applications, including transparent conductors, UV photodetectors, luminescent devices, and catalysis, which are clearly and comprehensively summarized in this work. Novel functional devices springing up from the newly developed ZnS‐based materials are highlighted as well. This review not only provides a scientific insight into the advances of ZnS‐based materials, but also touches on the future opportunities in this inspiring field. [ABSTRACT FROM AUTHOR]

Purpose: A type of in vivo dosimeter, an optically stimulated luminescent dosimeter, OSLD, may have dose sensitivity that depends on the angle of incidence of radiation. This work measures how angular dependence of a nanoDot changes with the geometry of the phantom in which irradiation occurs and with the intrinsic structure of the nanoDot. Methods: The OSLDs used in this work were nanoDot dosimeters (Landauer, Inc., Glenwood, IL), which were read with a MicroStar reader (Landauer, Inc., Glenwood, IL). Dose to the OSLDs was delivered by 6 MV x-rays. NanoDots with various intrinsic sensitivities were irradiated in numerous phantoms that had geometric shapes of cylinders, rectangles, and a cube. Results: No angular dependence was seen in cylindrical phantoms, cubic phantoms, or rectangular phantoms with a thickness to width ratio of 0.3 or 1.5. An angular dependence of 1% was observed in rectangular phantoms with a thickness to width of 0.433-0.633. A group of nanoDots had sensitive layers with mass density of 2.42-2.58 g/cm³ and relative sensitivity of 0.92-1.09 and no difference in their angular dependence. Within experimental uncertainty, nanoDot measurements agree with a parallel-plate ion chamber at a depth of maximum dose. Conclusions: When irradiated in cylindrical, rectangular, and cubic phantoms, nanoDots show a maximum angular dependence of 1% or less at an incidence angle of 90?. For a sample of 78 new nanoDots, the range of their relative intrinsic sensitivity is 0.92-1.09. For a sample of ten nanoDots, on average, the mass in the sensitive layer is 73.1% Al2O3:C and 26.9% polyester. The mass density of the sensitive layer of a nanoDot disc is between 2.42 and 2.58 g/cm³. The angular dependence is not related to Al2O3:C loading of the nanoDot disc. The nanoDot at the depth of maximum dose has no more angular dependence than a parallel-plate ion chamber. [ABSTRACT FROM AUTHOR]

Purpose: Lung cancer treatment is susceptible to treatment errors caused by interfractional anatomical and respirational variations of the patient. On-board treatment dose verification is especially critical for the lung stereotactic body radiation therapy due to its high fractional dose. This study investigates the feasibility of using cone-beam (CB)CT images estimated by a motion modeling and free-form deformation (MM-FD) technique for on-board dose verification. Methods: Both digital and physical phantom studies were performed. Various interfractional variations featuring patient motion pattern change, tumor size change, and tumor average position change were simulated from planning CT to on-board images. The doses calculated on the planning CT (planned doses), the on-board CBCT estimated by MM-FD (MM-FD doses), and the on-board CBCT reconstructed by the conventional Feldkamp-Davis-Kress (FDK) algorithm (FDK doses) were compared to the on-board dose calculated on the "gold-standard" on-board images (gold-standard doses). The absolute deviations of minimum dose (?Dmin), maximum dose (?Dmax), and mean dose (?Dmean), and the absolute deviations of prescription dose coverage (?V100%) were evaluated for the planning target volume (PTV). In addition, 4D on-board treatment dose accumulations were performed using 4D-CBCT images estimated by MM-FD in the physical phantom study. The accumulated doses were compared to those measured using optically stimulated luminescence (OSL) detectors and radiochromic films. Results: Compared with the planned doses and the FDK doses, the MM-FD doses matched much better with the gold-standard doses. For the digital phantom study, the average (± standard deviation) ?Dmin, ?Dmax, ?Dmean, and ?V100% (values normalized by the prescription dose or the total PTV) between the planned and the gold-standard PTV doses were 32.9% (±28.6%), 3.0% (±2.9%), 3.8% (±4.0%), and 15.4% (±12.4%), respectively. The corresponding values of FDK PTV doses were 1.6% (±1.9%), 1.2% (±0.6%), 2.2% (±0.8%), and 17.4% (±15.3%), respectively. In contrast, the corresponding values of MM-FD PTV doses were 0.3% (±0.2%), 0.9% (±0.6%), 0.6% (±0.4%), and 1.0% (±0.8%), respectively. Similarly, for the physical phantom study, the average ?Dmin, ?Dmax, ?Dmean, and ?V100% of planned PTV doses were 38.1% (±30.8%), 3.5% (±5.1%), 3.0% (±2.6%), and 8.8% (±8.0%), respectively. The corresponding values of FDK PTV doses were 5.8% (±4.5%), 1.6% (±1.6%), 2.0% (±0.9%), and 9.3% (±10.5%), respectively. In contrast, the corresponding values of MM-FD PTV doses were 0.4% (±0.8%), 0.8% (±1.0%), 0.5% (±0.4%), and 0.8% (±0.8%), respectively. For the 4D dose accumulation study, the average (± standard deviation) absolute dose deviation (normalized by local doses) between the accumulated doses and the OSL measured doses was 3.3% (±2.7%). The average gamma index (3%/3 mm) between the accumulated doses and the radiochromic film measured doses was 94.5% (±2.5%). Conclusions: MM-FD estimated 4D-CBCT enables accurate on-board dose calculation and accumulation for lung radiation therapy. It can potentially be valuable for treatment quality assessment and adaptive radiation therapy. [ABSTRACT FROM AUTHOR]

Scintillating screens are commonly used at accelerator facilities. However, their imaging qualities are not well understood, especially for high-current ion beam operation. Several types of inorganic scintillators were investigated for various ion species and energies of 4.8 and 11.4 MeV/u. For ion beam applications, the exact reproduction of the beam profile is of great importance. Due to the impact by ions, the dose rate during beam delivery is more than 10 orders of magnitude higher as for other applications of scintillators in typical nuclear physics experiments. To validate the imaging quality of the scintillators, different profile measurement methods are compared. Ceramic Al2O3 showed the best results compared to other ceramics like ZrO2:Y or quartz glass Herasil 102. The imaging properties of the materials can depend significantly on the ion energy. For Al2O3 irradiated with a Ca beam the of 4.8 MeV/u, the results agree with the reference methods. However, for 11.4 MeV/u, the screen image does not reflect the beam distribution, which cannot be attributed to material degradation. A model is under development taking into account the radial dose distribution along the ion track as well as the overlap of tracks. For Al2O3, this model can describe the observed saturation effect and is able to reconstruct saturated images. The basics and applications of this model are discussed. Detailed spectroscopic investigations were performed to determine the influence of the ion beam intensity on the luminescence spectra emitted by the materials. No significant dependence on the spectra with respect to the beam intensity was found for most of the scintillators. [ABSTRACT FROM PUBLISHER]

Solid-state lighting is a rapidly evolving technology, now virtually certain to someday displace traditional lighting in applications ranging from the lowest-power spot illuminator to the highest-power area illuminator. Moreover, it has considerable headroom for continued evolution even after this initial displacement. In this paper, we present a high-level overview of solid-state lighting, with an emphasis on white lighting suitable for general illumination. We characterize in detail solid-state lighting's past and potential-future evolution using various performance and cost metrics, with special attention paid to inter-relationships between these metrics imposed by human factors, technology, and economic considerations. [ABSTRACT FROM AUTHOR]

At GSI, the Helmholtz Centre for Ion Research, the properties of scintillation screens, irradiated by an ion beam, were studied. For various materials, the different ion beams H+, C2+, Ar10+, Ni9+, Ta24+, and U28+ in the energy range from 4.8-11.4 MeV/u were applied with currents ranging from nA to some mA, delivered by the heavy ion LINAC at GSI. Scintillation screens are widely used for qualitative ion beam profile monitoring. However, precise measurements of the beam profile yield ambivalent results, especially for high beam currents. Thus, the properties (light yield, beam width, and higher statistical moments) of well-known scintillators, ceramic materials, and different quartz glasses are compared. The image of each ion beam pulse was recorded by a digital CCD camera and individually evaluated. A change of the imaged ion beam shape was observed for some materials. The recorded beam profile shows dependence on the scintillator material. Even for low beam intensities (17 nA) a difference in the beam width of about 25% was measured. Additionally, the light yield and beam width depend significantly on the screen temperature, which is increased by the ion impact. For ZrO2 : Al the influence of the screen temperature on the statistical moments was investigated. Furthermore the spectra of scintillation screens were studied in the region from 350 to 750 nm for the irradiation with H+ and Ta24+ ions. Empirical results are discussed and give rise to further investigations on the materials. [ABSTRACT FROM AUTHOR]

The infrared light emission of forward-biased silicon diodes is studied. Through ion implantation and anneal, dislocation loops were created near the diode junction. These loops suppress the light emission at the band-to-band peak around 1.1 µm. The so-called D1 line at 1.5 µm is strongly enhanced by these dislocation loops. We report a full study of photoluminescence and electroluminescence of these diodes. The results lead to new insights for the manufacturing approach of practical infrared light sources in integrated circuits. [ABSTRACT FROM AUTHOR]

A narrowband luminescent coating for germicidal 254-nm ultraviolet optical fiber sensors has been developed. A mixture of phosphor and epoxy is used for this coating. The luminescent-clad sensing principle uses a fiber, which has had its cladding and jacket both removed, and a photoluminescent coating replacing the cladding. As the coating luminesces, part of the emission is coupled to the fiber core through evanescent wave coupling. The combined absorption spectrum of the phosphor and the transmission spectrum of the epoxy result in a narrow sensitivity band of wavelengths being detected, centered around 254 nm. The absorption of the 254-nm radiation incident on the coating is emitted as visible light in the optical fiber sensor. This paper describes the development and testing of this narrowband coating using a spectrophotometer to examine its responsivity, and a luminescent-coated optical fiber sensor is compared with a UV photodiode when illuminated by a UV lamp. This optical fiber sensor monitors the output of UV lamps for stabilization and control purposes. [ABSTRACT FROM PUBLISHER]

We describe a novel biochemical sensing method and its potential new biosensing applications. A light-sensitive complementary metal oxide semiconductor (CMOS) chip prepared through a standard 0.5-μm CMOS process was developed for measuring biochemical reactions. A light producing enzymatic reaction catalyzed by horseradish peroxidase (HRP) was designed as a platform reaction to determine the concentration of hydrogen peroxide (H2O2) by the CMOS chip with a standard semiconductor parameter analyzer (HP4145). The kinetics of enzymatic reaction were determined and compared with a standard and sophisticated fluorometer (Hitachi F-4500) in a biochemical laboratory. Similar results were obtained by both instruments. Using glucose oxidase as an example, we further demonstrated that the HRP platform can be used to determine other H2O2 producing reactions with the CMOS system. The result points to an important application of the CMOS chip in biological measurements and in diagnosis of various health factors. [ABSTRACT FROM PUBLISHER]

Glass-clad crystal fibers were grown using the codrawing laser-heated pedestal growth method. Both single-clad and double-clad structures were attempted. Using a 446-nm laser diode as the pump, 2.45 mW of collimated broadband emission was generated with a 3-dB bandwidth of 180 nm. As much as 7.7 mW of output power with a 3-dB bandwidth of 182 nm was generated using a 532-nm solid-state pump laser. The broadband light source is advantageous to use in optical coherence tomography with an axial resolution of 1.5 in air and a low image pixel crosstalk. [ABSTRACT FROM PUBLISHER]

Contemporary silicon light-emitting diodes in silicon-on-insulator (SOI) technology suffer from poor efficiency compared to their bulk-silicon counterparts. In this letter, we present a new device structure where the carrier injection takes place through silicon slabs of only a few nanometer thick. Its external quantum efficiency of 1.4 · 10-4 at room temperature, with a spectrum peaking at 1130 nm, is almost two orders higher than reported thus far on SOI. The structure diminishes the dominant role of nonradiative recombination at the n+ and p+ contacts, by confining the injected carriers in an SOI peninsula. With this approach, a compact infrared light source can be fabricated using standard semiconductor processing steps. [ABSTRACT FROM AUTHOR]

Remarkably strong infrared light emission was recently observed from silicon p+-n diodes. In several publications a causal relation is proposed between the larger-than-expected light intensity and the existence of lattice damage around the junction. In this letter, we present direct experimental evidence that lattice damage is in fact detrimental to the efficiency of light emission of silicon LEDs. The experiments call for a revision of the explanation for strong light emission in this type of devices. [ABSTRACT FROM AUTHOR]

An initial demonstration is reported in terms of maximising performance of photovoltaic modules. Experimental results of a triple junction solar cell covered with a 3 mm red‐emitting luminous glass which can be efficiently excited by ultraviolet light indicate that this combination exhibits significantly enhanced efficiency of 36.5% under one‐sun of AM1.5G. Integrating a luminescent (LSC) glass onto modules without converting any fabrication process at the device level is considered to be one of the predominant advantages of this device. Additionally, in order to achieve strong visible emission, it is mandatory to determine a thickness of LSC coverglass due to the edge reflection. [ABSTRACT FROM AUTHOR]