Development and Verification of a 480 nm Blue Light Enhanced/Reduced Human-Centric LED for Light-Induced Melatonin Concentration Control.

With the inherent sleep and wake cycle regulated by natural sunlight, the human body has evolved over millennia to be active during the day and to rest at night. However, maintaining an optimal 24 h cycle has become increasingly problematic in modern society as more people spend the majority of the day indoors. Many research groups have reported that inadequate artificial lighting interferes with melatonin production and disrupts the circadian rhythm.

Molecular Mechanism of Selective AlO Atomic Layer Deposition on Self-Assembled Monolayers.

Area-selective atomic layer deposition (AS-ALD) of insulating metallic oxide layers could be a useful nanopatterning technique for making increasingly complex semiconductor circuits. Although the alkanethiol self-assembled monolayer (SAM) has been considered promising as an ALD inhibitor, the low inhibition efficiency of the SAM during ALD processes makes its wide application difficult. We investigated the deposition mechanism of AlO on alkanethiol-SAMs using temperature-dependent vibrational sum-frequency-generation spectroscopy.

Soft, adhesive and conductive composite for electroencephalogram signal quality improvement.

Since electroencephalogram (EEG) is a very small electrical signal from the brain, it is very vulnerable to external noise or motion artifact, making it difficult to measure. Therefore, despite the excellent convenience of dry electrodes, wet electrodes have been used. To solve this problem, self-adhesive and conductive composites using carbon nanotubes (CNTs) in adhesive polydimethylsiloxane (aPDMS), which can have the advantages of both dry and wet electrodes, have been developed by mixing them uniformly with methyl group-terminated PDMS.

Isolation of Bovine Milk Exosome Using Electrophoretic Oscillation Assisted Tangential Flow Filtration with Antifouling of Micro-ultrafiltration Membrane Filters.

Tangent flow-driven ultrafiltration (TF-UF) is an efficient isolation process of milk exosomes without morphological deformation. However, the TF-UF approach with micro-ultrafiltration SiN membrane filters suffers from the clogging and fouling of micro-ultrafiltration membrane filter pores with large bioparticles. Thus, it is limited in the long term, continuous isolation of large quantities of exosomes.

Self-Repairable Silicon Anodes Using a Multifunctional Binder for High-Performance Lithium-Ion Batteries.

Despite of extremely high theoretical capacity of Si (3579 mAh g ), Si anodes suffer from pulverization and delamination of the electrodes induced by large volume change during charge/discharge cycles. To address those issues, herein, self-healable and highly stretchable multifunctional binders, polydioxythiophene:polyacrylic acid:phytic acid (PEDOT:PAA: PA, PDPP) that provide Si anodes with self-healability and excellent structural integrity is designed. By utilizing the self-healing binder, Si anodes self-repair cracks and damages of Si anodes generated during cycling.

Passivation and Interlayer Effect of Zr(i-PrO) on Green CuGaS/ZnS/Zr(i-PrO)@AlO and Red CuInS/ZnS/Zr(i-PrO)@AlO QD Hybrid Powders.

Broadband emissive I-III-VI quantum dots (QDs) are synthesized as efficient and stable I-III-VI QDs to be used as eco-friendly luminescent materials in various applications. Here, we introduce the additional passivation of zirconium isopropoxide (Zr(i-PrO)) to improve the optical properties and environmental stability of green-emitting CuGaS/ZnS (G-CGS/ZnS) and red-emitting CuInS/ZnS (R-CIS/ZnS) QDs. The photoluminescence quantum yield (PLQY) of both resultant Zr(i-PrO)-coated G-CGS/ZnS and R-CIS/ZnS QDs reaches similar values of ~ 95%.

Synthesis of CsMnBr Green Phosphors Using an Eco-Friendly Evaporative Crystallization Process.

Green (G) and red (R) light-emitting materials, such as quantum dots, perovskite nanocrystals, and inorganic phosphor powders, owing to their excellent optical characteristics, have attracted researchers' attention as color-conversion materials for lighting and display applications. However, these materials contain environmentally harmful elements, such as Pb or Cd, and/or they are synthesized using environmentally harmful synthetic approaches and conditions, involving the use of organic solvents, high pressure, high temperature, harsh atmosphere, and long reaction time. In this study, as an eco-friendly synthetic approach to synthesize lead-free CsMnBr G powder phosphor, we suggest an evaporative crystallization process of aqueous reactant solution.

Morphological-Electrical Property Relation in Cu(In,Ga)(S,Se) Solar Cells: Significance of Crystal Grain Growth and Band Grading by Potassium Treatment.

Solution-processed Cu(In,Ga)(S,Se)  (CIGS) has a great potential for the production of large-area photovoltaic devices at low cost. However, CIGS solar cells processed from solution exhibit relatively lower performance compared to vacuum-processed devices because of a lack of proper composition distribution, which is mainly instigated by the limited Se uptake during chalcogenization. In this work, a unique potassium treatment method is utilized to improve the selenium uptake judiciously, enhancing grain sizes and forming a wider bandgap minimum region.

-Inspired Intelligent Hydrochromic Adhesive Film.

-inspired hydrochromic nano/microstructured films have received much attention for its promising smart hydrochromic applications owing to their simple and low-cost but energy-effective strategy. A new type of water-switchable glazing film patterned with various nano/micro air-hole inverse opal arrays is introduced by selectively removing nano/microsphere polystyrene arrays embedded in the surface of polydimethylsiloxane (PDMS) films. Using the significant contrast ratio of the bleaching and the scattering states, we have optimized the switching properties of Mie scattered patterns.

Narrow-Band SrMgAlO:Eu, Mn Green Phosphors for Wide-Color-Gamut Backlight for LCD Displays.

The strength of the photoluminescence excitation (PLE) spectrum of SrMgAlO:Eu, Mn (SAM:Eu, Mn) phosphor increased at deep blue (∼430 nm) and red-shifted from violet to deep blue with increasing concentrations of both Eu ions Mn ions. Eu-Mn energy transfer between Eu ions in Sr-O layer and Mn ions at Al-O tetrahedral sites was maximized, and the photoluminescence (PL) intensity of the narrow-band Mn emission was improved by optimizing the concentrations of Eu and Mn ions. The PL emission spectrum of the (SrEu)(MgMn)AlO (SAM:Eu, Mn) phosphor peaks was optimized at 518 nm at a full width at half-maximum (FWHM) of 26 nm under light-emitting diode (LED) excitation at 432 nm LED.

Newly Developed Broadband Antireflective Nanostructures by Coating a Low-Index MgF Film onto a SiO Moth-Eye Nanopattern.

A newly developed nanopatterned broadband antireflective (AR) coating was fabricated on the front side of a glass/indium tin oxide/perovskite solar cell (PSC) by depositing a single interference layer onto a two-dimensional (2D)-patterned moth-eye-like nanostructure. The optimized developed AR nanostructure was simulated in a finite-difference time domain analysis. To realize the simulated developed AR nanostructure, we controlled the SiO moth-eye structure with various diameters and heights and a MgF single layer with varying thicknesses by sequentially performing nanosphere lithography, reactive ion etching, and electron-beam evaporation.

Stable and Colorful Perovskite Solar Cells Using a Nonperiodic SiO/TiO Multi-Nanolayer Filter.

While research on building-integrated photovoltaics (BIPVs) has mainly focused on power-generating window applications, the utilization of other underutilized surface areas in buildings, including exteriors, facades, and rooftops, has still not been fully explored. The most important requirements for BIPVs are color, power conversion efficiency (PCE), and long-term stability. In this work, we achieved colorful (red, green, blue, RGB) perovskite solar cells (PSCs) with minimized PCE loss (<10%) and enhanced photostability by exploiting the optical properties of nonperiodic multi-nanolayer, narrow-bandwidth reflective filters (NBRFs).

Dual wavelength lasing of InGaN/GaN axial-heterostructure nanorod lasers.

Optical confinement effects are investigated in InGaN/GaN axial-heterostructure nanolasers. Cylindrical nanorods with GaN/InGaN/GaN structures are prepared using combined processes of top-down and bottom-up approaches. The lasing of InGaN is observed at a low threshold (1 μJ cm-2), which is attributed to an efficient carrier transfer process from GaN to InGaN.

Stable and Efficient Green Perovskite Nanocrystal-Polysilazane Films for White LEDs Using an Electrospray Deposition Process.

We successfully fabricated a stable, efficient, and easy-to-use CsPbBr perovskite nanocrystal (PeNC)-embedded inorganic polymer film through an encapsulation step with a Si-N/Si-O-based polysilazane (PSZ) matrix via the electrospray (e-spray) deposition of a silazane (SZ) oligomer-decorated PeNC solution. To eliminate Pb defect sites that are generated when the ligands are peeled from the PeNC surface, surface passivation of the Lewis acid/base adduct is possible by coupling the SZ oligomer (the donor of lone pairs) with Pb sites (the acceptor of lone pairs). With the addition of the SZ oligomer, the photoluminescence quantum yield of photodegraded CsPbBr PeNC was recovered and increased by 2.

RGB-Colored Cu(In,Ga)(S,Se) Thin-Film Solar Cells with Minimal Efficiency Loss Using Narrow-Bandwidth Stopband Nano-Multilayered Filters.

Colorful Cu(In,Ga)(S,Se) (CIGSSe) thin-film solar cells were achieved by integrating a narrow-bandwidth stopband filter (NBSF) on a CIGSSe cell. The full range of visible color of NBSF could be realized by depositing one-dimensional nano-multilayers of alternating high-index (AlO) and low-index (SiO) films while controlling the thickness of each layer and the number of stacked layers. Particularly, high-purity red, green, and blue (RGB) colors were generated on black CIGSSe cells with minimal harvest efficiency drop, showing power conversion efficiency (PCE) losses for the red and green CIGSSe cells of 4.

Low-Yellowing Phosphor-in-Glass for High-Power Chip-on-board White LEDs by Optimizing a Low-Melting Sn-P-F-O Glass Matrix.

We introduce a low-melting-point (MP) Sn-P-F-O glass ceramic material into the phosphor-in-glass (PIG) material to realize an 'on-chip' chip-on-board (COB) type of phosphor-converted (pc) white light-emitting diode (WLED) with green (BaSr)SiO:Eu and red (SrCa)AlSiN:Eu (SCASN) phosphors. The optimum Sn-P-F-O-based ceramic components can be sintered into the glass phase with a facile one-step heating process at 285 °C for 1 min. Specifically, these soft-fabrication conditions can be optimized to minimize the degradation of the luminescent properties of the red SCASN phosphor as well as the green silicate phosphor in PIG-based white COB-type pc-LEDs owing to the low thermal loss of the phosphors at low fabrication temperatures below 300 °C.

Efficient and Stable CsPbBr Quantum-Dot Powders Passivated and Encapsulated with a Mixed Silicon Nitride and Silicon Oxide Inorganic Polymer Matrix.

Despite the excellent optical features of fully inorganic cesium lead halide (CsPbX) perovskite quantum dots (PeQDs), their unstable nature has limited their use in various optoelectronic devices. To mitigate the instability issues of PeQDs, we demonstrate the roles of dual-silicon nitride and silicon oxide ligands of the polysilazane (PSZ) inorganic polymer to passivate the surface defects and form a barrier layer coated onto green CsPbBr QDs to maintain the high photoluminescence quantum yield (PLQY) and improve the environmental stability. The mixed SiN /SiN O /SiO passivated and encapsulated CsPbBr/PSZ core/shell composite can be prepared by a simple hydrolysis reaction involving the addition of adding PSZ as a precursor and a slight amount of water into a colloidal CsPbBr QD solution.

Enhanced DC-Operated Electroluminescence of Forwardly Aligned p/MQW/n InGaN Nanorod LEDs via DC Offset-AC Dielectrophoresis.

We introduce an orientation-controlled alignment process of p-GaN/InGaN multiquantum-well/n-GaN (p/MQW/n InGaN) nanorod light-emitting diodes (LEDs) by applying the direct current (DC) offset-alternating current (AC) or pulsed DC electric fields across interdigitated metal electrodes. The as-forwardly aligned p/MQW/n InGaN nanorod LEDs by a pulsed DC dielectrophoresis (DEP) assembly process improve the electroluminescence (EL) intensities by 1.8 times compared to the conventional AC DEP assembly process under DC electric field operation and exhibit an enhanced applied current and EL brightness in the current-voltage and EL intensity-voltage curves, which can be directly used as the fundamental data to construct DC-operated nanorod LED devices, such as LED areal surface lightings, scalable lightings (micrometers to inches) and formable surface lightings.

Origin of highly efficient photoluminescence in AgInS nanoparticles.

The photoluminescence of AgInS nanoparticles was examined to clarify the emissive relaxation processes of defect states and to explain the highly efficient photoluminescence of defect states. The large Stokes shift of the defect emission was explained by strong electron-phonon coupling in the nanoparticles. Steady-state and time-resolved photoluminescence spectroscopy indicated two emissive defect states with characteristic emission energies and lifetimes.

Circadian-tunable Perovskite Quantum Dot-based Down-Converted Multi-Package White LED with a Color Fidelity Index over 90.

New metrics of the color and circadian performances of down-converted white light-emitting diodes (DC-WLEDs) are rapidly becoming popular in smart lighting systems. This is due to the increased desire for accurate analytical methods to measure the effects of newly developed quantum dot (QD)-based lighting on the vision, color, and circadian sensors of retina cells in the human eye. In this regard, a two-measure system known as technical memorandum TM-30-2015 (Illuminating Engineering Society of North America), encompassing the color fidelity index (CFI, R ) and the color gamut index (CGI, R ), has been developed as a new metrics of color to replace the currently utilized color rendering index (CRI, R ).

Multiple-Color-Generating Cu(In,Ga)(S,Se) Thin-Film Solar Cells via Dichroic Film Incorporation for Power-Generating Window Applications.

There are four prerequisites when applying all types of thin-film solar cells to power-generating window photovoltaics (PVs): high power-generation efficiency, longevity and high durability, semitransparency or partial-light transmittance, and colorful and aesthetic value. Solid-type thin-film Cu(In,Ga)S (CIGS) or Cu(In,Ga)(S,Se) (CIGSSe) PVs nearly meet the first two criteria, making them promising candidates for power-generating window applications if they can transmit light to some degree and generate color with good aesthetic value. In this study, the mechanical scribing process removes 10% of the window CIGSSe thin-film solar cell with vacant line patterns to provide a partial-light-transmitting CIGSSe PV module to meet the third requirement.

Cycles of circadian illuminance are sufficient to entrain and maintain circadian locomotor rhythms in Drosophila.

Light at night disrupts the circadian clock and causes serious health problems in the modern world. Here, we show that newly developed four-package light-emitting diodes (LEDs) can provide harmless lighting at night. To quantify the effects of light on the circadian clock, we employed the concept of circadian illuminance (CIL).

High-efficiency red electroluminescent device based on multishelled InP quantum dots.

We report on the synthesis of highly fluorescent red-emitting InP quantum dots (QDs) and their application to the fabrication of a high-efficiency QD-light-emitting diode (QLED). The core/shell heterostructure of the QDs is elaborately tailored toward a multishelled structure with a composition-gradient ZnSeS intermediate shell and an outer ZnS shell. Using the resulting InP/ZnSeS/ZnS QDs as an emitting layer, all-solution-processible red InP QLEDs are fabricated with a hybrid multilayered device structure having an organic hole transport layer (HTL) and an inorganic ZnO nanoparticle electron transport layer.