Simulation and design of folded perovskite x-ray detectors

A variety of medical, industrial, and scientific applications requires highly sensitive and cost-effective x-ray detectors for photon energies ranging from keV to MeV. Adapting the thickness of polycrystalline or single crystal conversion layers especially to high-energy applications increases the complexity of fabrication and potentially decreases the performance of conventional direct conversion x-ray detectors. To tackle the challenges with respect to the active layer thickness and to combine the superior performance of single crystal materials with the low-cost nature of polycrystalline conversion layers, we investigate thin film x-ray detector technologies based on a folded device architecture. Analytical models simulating the sensitivity and the detective quantum efficiency (DQE) are used to evaluate the performance of folded detectors based on polycrystalline organic-inorganic perovskite semiconductors in various layout configurations and for different photon energies. Simulations of folded perovskite devices show high sensitivities. The DQE analysis introduces additional noise related boundary conditions for the folding length. A comparison with conventional detectors based on state of the art conversion materials at different photon energies demonstrates the potential of the folded detector layout as simulated sensitivities are comparable to single crystal detectors

Asymmetric L-shaped resonant optical antennas with plasmon length tuning and high-electric field enhancement

L-shaped resonant optical antennas (ROAs) are low-symmetry plasmonic nanostructures with the unique ability to show two tunable resonances in the optical and near-infrared wavelength regions. The plasmon length of the so-called longitudinal dipolar fundamental plasmon mode of these asymmetric L-shaped ROAs can be used as plasmon resonance building blocks to design polarization-sensitive devices. This paper introduces and numerically analyzes a novel design of asymmetric L-shape ROAs. The reported design offers two resonance modes, i.e., bimodal longitudinal antenna resonance behavior with a high enhancement factor. These two resonances can be selectively excited by changing the linear polarization angle. It is found that the coupled L-shaped ROA with a very small 2 nm gap width exhibits field enhancements 40 and 147.3 on scale |ETOT|/|EIN| for the high energy and low energy resonance, respectively. The obtained results and the analysis open a new route for multiple plasmon resonance devices with ultra-high field enhancement that can be easily integrated with future nano-optical circuits with multiple operational frequencies

Automated Quantitative Quality Assessment of Printed Microlens Arrays

We propose an automated evaluation pipeline uti-lizing both bright field light and confocal microscope imagesas well as multiple quality measures to quantitatively evaluatethe quality of printed microlens arrays

A Review on Quantum Dot‐Based Color Conversion Layers for Mini/Micro‐LED Displays: Packaging, Light Management, and Pixelation

Mini/microlight-emitting diodes (LEDs) are one of the most promising technologies for next-generation displays to meet the requirements of demanding applications, including augmented reality/virtual reality displays, wearable devices, and microprojectors. To realize full-color displays, the strategy of combining miniaturized blue nitride-based LEDs with color conversion layers is promising due to the high efficiencies of the LEDs and the advantageous manufacturing. Quantum dots (QDs), owing to their high photoluminescence quantum yield, small particle size, and solution processability, have emerged as the color conversion material with the most potential for mini/micro-LEDs. However, the integration of QDs into display technologies poses several challenges. From the material side, the stability of QD materials is still challenging. For the case of packaging QDs in a matrix, the dispersion quality of QDs and the light extraction of the emission need to be improved. From the fabrication side, the lack of high-precision mass manufacturing strategies in QD pixelation hinders the widespread application of QDs. Toward the issues above, this review summarizes the research on QD materials for color conversion display in recent years to systematically draw an overview of the packaging strategies, the light management approaches, and the pixelation methods of QD materials toward mini/micro-LED-based display technologies

Role of packing density and spatial correlations in strongly scattering 3D systems

Discrete random media have been investigated extensively over the past century due to their ability to scatter light. Even so, the link between the three-dimensional (3D) spatial distribution of the scattering elements and the resulting opacity is still lively debated to date due to different experimental conditions, range of parameters explored, or sample formulations. On the other hand, a unified numerical survey with controlled parameters has been impractical up to date due to the sheer computational power required to address samples with representative size. In this work, we exploit a graphics processing unit implementation of the T-matrix method to investigate the complete range of particle volume concentration and packing-induced spatial correlations, allowing us to reveal and elucidate a twofold role played by spatial correlations in either enhancing or suppressing opacity. By applying these findings to the illustrative case of white paint, we determine the optimal combination of density and spatial correlations corresponding to the highest opacity. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen

Recent Progress in Light‐Scattering Porous Polymers and Their Applications

Conventional inorganic-nanoparticles-based scattering systems have dominated many practical applications for years. In contrast, the rise of porous polymers is perceived as a game-changer due to their low cost, facile preparation, and great abundance. One challenging issue to be tackled is the design and fabrication of porous polymers with light-scattering properties comparable to those of inorganic nanoparticles. Taking inspiration from nature (e.g., from white beetles Cyphochilus), scientists have achieved remarkable progress in the field of light-scattering porous polymers and their related applications in recent years. Therefore, here, an up-to-date review about this emerging field is provided. This overview covers materials for making porous polymer structures, detailed fabrication methods, and applications benefitting from their tailorable light-scattering properties. It is envisioned that more bioinspired light-scattering porous polymers will be made to be potential alternatives of conventional nanoparticles-based scatterers

Development and characterization of adjustable refractive index scattering epoxy acrylate polymer layers

Several polymer films for improved optical properties in optoelectronic devices are presented. In such optical applications, it is sometimes important to have a film with an adjusted refractive index, scattering properties, and a low surface roughness. These diffusing films can be used to increase the efficiency of optoelectronic components, such as organic light-emitting diodes. Three different epoxy acrylate mixtures containing Syntholux 291 EA, bisphenol A glycerolate dimethacrylate, and Sartomer SR 348 L are characterized and optimized with different additives. The adjustable refractive index of the material is achieved by chemical doping using 9-vinylcarbazole.Titanium nanoparticles in the mixtures generate light scattering and increase the refractive index additionally. A high-power stirrer is used to mix and disperse all chemical ubstances together to a homogenousmixture. The viscosity behavior of the mixtures is an important property for the selection of the production method and, therefore, the viscosity measurement results are presented. After the mixing, the monomer mixture is applied on glass substrates by screen printing. To initiate polymerization, the produced films are irradiated for 10 min with ultraviolet radiation and heat. Transmission measurements of the polymer matrix and roughness measurements complement the characterization