Light Emission Research Articles

Dual-emissive BT-CP-TD covalent organic polymers for detecting furacillin, white light emission and information encryption

Recently, luminescent covalent organic polymers (LCOPs) are garnering more and more attention owing to their excellent emissive properties. However, the precise control of LCOPs’ luminescence behaviors remains a formidable challenge. Here, a dual-emissive CP-(BTxTD100-x) COP which was composited of CP, BT and TD (x is the added molar ratio of BT to total feed aldehyde) were synthesized by Knoevenagel condensation reaction between 1,3,5-tri(4-cyano-methylbenzene) benzene (CP) and 2,7-dibenzaldehyde-benthiadiazole (BT)/1,4-bis(4-aldehyde phenyl)benzene (TD). The luminescent behaviors of CP-(BTxTD100-x) COP could be precisely tuned by the ratio of CP, BT and TD as well as excitation wavelength. The CP-(BT33TD67) COP emitted white light (0.3012, 0.3207) when excited at 310 nm. A ratiometric fluorescence sensor was developed for detecting furacillin using CP-(BT33TD67) COP, showing a detection limit of 8.23 ng mL−1. Based on the excitation-depending behaviors of CP-(BT33TD67) COP, combined with CP-(BT100TD0) COP, a kind of security and information encryption image in the form of a quick response was designed. The discoveries provide a new idea for the design of dual-emission LCOPs by regulating the ratio of monomers and excitation wavelengths. The findings also extend the potential applications of dual-emission LCOPs.

All-solution-processed perovskite-quantum-dot light-emitting diodes through effective synergistic combination of orthogonal solvent and electron transport material

Perovskite quantum dots (PQDs) have shown great promise for use in photovoltaic devices, due to their ability to offer advantages such as tunability of visible light and efficient light emission. This study demonstrates the successful utilization of a triazine-based PO-T2T (2,4,6-Tris[3(diphenylphosphenyl)phenyl]-1,3,5-triazine; PO-T2T) as the electron transport layer (ETL) through an all-solution process. To improve the structural and optical characterization of CsPbBr3 and CsPbI3 QDs, three organic solvents, namely chlorobenzene, methyl acetate, and ethyl acetate, were selected to find an effective orthogonal solvent for PO-T2T. The all-solution processed devices incorporating PO-T2T and Methyl acetate (MeOAc) demonstrated impressive external quantum efficiencies of 5.57% for CsPbBr3 and 1.60% for CsPbI3 QDs. Notably, these devices also achieved the highest maximum luminance among all-solution processed PQDs-LEDs, with values of 33334 cd m–2 for CsPbBr3 and 224 cd m–2 for CsPbI3 QDs.

Enhancing CdSe/ZnS Quantum-Dot Light-Emitting Diode Performance: The Impact of Thermal Treatment Atmospheres on Fabrication Processes

We explored the thermal treatment impact on the performance of quantum-dot light-emitting diodes (QLEDs). The QLEDs comprised multiple layers: a 2.2-μm thick epoxy buffer layer; a bottom cathode composed of 12-nm MoOx/10-nm Ag/12-nm MoOx; a 20-nm ZnO electron transporting layer (ETL); a 10-nm CdSe/ZnS quantum dot light emission layer (EML); a 40-nm 4,4′,4″-Tris(carbazol-9-yl) triphenylamine hole transporting layer; a 10-nm WOx hole injection layer; and a 100-nm Ag top anode. We applied thermal treatments to the cathode, ETL, and EML separately to assess their effects on the QLEDs. Additionally, we evaluated the impact of the thermal treatment atmosphere. Vacuum thermal treatment on the cathode and EML resulted in minor improvements in QLED performance, whereas treatment of the ETL led to a decline in performance. In contrast, air thermal treatment on the cathode and EML decreased QLED performance but significantly improved it by 15% in current efficiency when applied to the ETL. The performance differences attributable to the thermal treatment atmosphere are likely due to ligand removal and oxidation processes, facilitated by thermal energy and oxygen. Our study highlights that air thermal treatment on the ETL substantially improves QLED performance, offering crucial insights into the significance of thermal treatment in QLED development.

Light pollution affects activity differentially across breeding stages in an urban exploiter: an experiment in the house sparrow (Passer domesticus)

Artificial Light At Night (ALAN) is a major urban perturbation, which can have detrimental effects on wildlife. Recent urban planning has led to an increased use of white light emission diodes (LEDs) in cities. However, little is known about the effects of this type of ALAN on wild vertebrates, especially during reproduction. We designed an experiment to test the impact of ALAN on the activity rhythms (daily time of first activity (TFA) and time of last activity (TLA)) of captive House sparrows (Passer domesticus) during several reproductive stages (from pre-breeding to post-breeding). We also tested the impact of ALAN on reproductive performance (laying date, clutch size, hatching and fledging success). Experimental birds were active earlier in the morning (earlier TFA) relative to controls although experimental and control birds did not differ in their TLA. The effect of ALAN on TFA was apparent during specific stages only (pre-breeding and chick-rearing stages), suggesting that sparrows actively adjust their activity in response to ALAN only during specific periods. This impact of ALAN on activity did not persist through the whole breeding season, suggesting that sparrows may habituate to ALAN. Alternatively, they may not be able to sustain a long-term increased activity in response to ALAN because of sleep deprivation and related physiological costs. Finally, we did not find any impact of ALAN on the reproductive performance of captive house sparrows held under optimal conditions. This suggests that ALAN may not be dramatically detrimental to the reproduction of this urban exploiter, at least when food availability is not constraining.

Структура, ріст та оптичні характеристики монокристалів сульфанілату гуанідинію (GSA)

Guanidine Sulphanilate (GSA) single crystal was grown by slow evaporation growth method. Single crystal X-ray diffraction studies show that the crystal grows in a centro symmetric monoclinic system and its space group is P21/c. Optical studies were carried out using UV visible spectroscopy and the grown crystal shows the the lower cutoff wavelength of 220 nm. Photoluminescence studies show that GSA crystals have good luminescence properties. Laser damage threshold was found to be 0.24GW/cm2. Nonlinear optical studies show green light emission.

Ultraviolet electroluminescence with electrically tunable colour from epitaxial n-(0001)ZnO/p-(0001)GaN light-emitting diodes

Abstract Pulsed laser deposition (PLD) technique is used to grow unintentionally n-type (0001)ZnO layers with high crystalline and morphological qualities on p-type (0001)GaN/sapphire templates. Electroluminescent devices are fabricated on these p-n heterojunctions. Oxygen pressure during growth has been found to influence strongly the crystalline and defect properties of the grown layers, which affect not only the current-voltage characteristics but also the emission properties of the electroluminescent devices. It has been observed that the electroluminescence (EL) spectra have both defects related visible and band-edge related ultraviolet (UV) transition features stemming from both GaN and ZnO sides. The study reveals that UV to visible EL intensity ratio maximizes at an optimum oxygen pressure. The relative contribution of EL originating from ZnO and GaN sides can be tuned by the applied bias, as the bias can control the depletion width and hence the carrier interdiffusion across the junction. This finding thus offers a scope to electrically tune the color of the emitted light in these devices.

Tunable exciton valley-pseudospin orders in moiré superlattices.

Excitons in two-dimensional (2D) semiconductors have offered an attractive platform for optoelectronic and valleytronic devices. Further realizations of correlated phases of excitons promise device concepts not possible in the single particle picture. Here we report tunable exciton "spin" orders in WSe2/WS2 moiré superlattices. We find evidence of an in-plane (xy) order of exciton "spin"-here, valley pseudospin-around exciton filling vex = 1, which strongly suppresses the out-of-plane "spin" polarization. Upon increasing vex or applying a small magnetic field of ~10 mT, it transitions into an out-of-plane ferromagnetic (FM-z) spin order that spontaneously enhances the "spin" polarization, i.e., the circular helicity of emission light is higher than the excitation. The phase diagram is qualitatively captured by a spin-1/2 Bose-Hubbard model and is distinct from the fermion case. Our study paves the way for engineering exotic phases of matter from correlated spinor bosons, opening the door to a host of unconventional quantum devices.

Light Intensity of Phosphorescent-Netting Pots and Determining Their Visibility to Snow Crab (Chionoecetes opilio) Using Visual Modeling Techniques

This study explores the visibility of phosphorescent-netting pots to snow crab (Chionoecetes opilio) using visual modeling techniques. Light emitted from such pots increases catch per unit effort, yet little is understood about the factors driving these higher catch rates. In this study, we measure pot light emission and snow crab visual acuity. Combining these data with estimates obtained in the literature for other biotic and abiotic factors, we model snow crab vision in relation to the pots. Utilizing these factors and environmental conditions, we derive a contrast ratio between the pot light and the ambient light. Findings reveal that the visibility of pot lights at 200-m depth depends primarily on solar angle (time of day) and time elapsed post-deployment. Additional factors influencing the vision of the pots include water column quality and benthic boundary layer turbidity. This study is the first to model the visual ecology of snow crab and the first to estimate snow crab visual acuity. These insights into snow crab visual ecology can potentially enhance fishing techniques, promote catch efficiency and sustainability, and help provide a path forward for visual ecology research in the fisheries science field.

Near-infrared and green light emission spectroscopic characteristics of Er3+ doped alumina–phosphate glasses

Near-infrared and green light emission spectroscopic characteristics of Er3+ doped alumina–phosphate glasses

КОФЕЙНАЯ КИСЛОТА СТИМУЛИРУЕТ СВЕЧЕНИЕ МИЦЕЛИЯ ВЫСШИХ ГРИБОВ NEONOTHOPANUS NAMBI, ARMILLARIA BOREALIS IN VIVO

In vivo experiments have shown that the addition of caffeic acid to the luminous mycelia of the higher fungi Neonothopanus nambi and Armillaria borealis stimulates a rapid and significant (by an order of magnitude or more) increase in the intensity of their light emission. It has been suggested that the observed effect of fungal luminescence activation may be mediated by the oxidation of caffeic acid by enzymes of the ligninolytic complex of basidiomycetes (in particular, by peroxidases) with the emission of visible light quanta. Comparative in vivo experiments showed that the addition of hispidin (the precursor of luciferin in the light emission reaction of higher fungi) did not affect the intensity of bioluminescence of the mycelia. At the same time, in vitro studies found that caffeic acid significantly suppressed the NADPH-hispidin-activated emission reaction of luminescent systems isolated from the mycelia of N. nambi and A. borealis. The inhibitory effect of caffeic acid is considered and discussed in the work from the standpoint of the classical biochemistry concept on enzyme inhibition by the reaction product according to the negative feedback principle. In general, the results obtained develop and supplement the understanding of the mechanisms of light emission in higher fungi and testify in favor of the fact that the generation of visible light quanta in basidiomycetes can be carried out by different biochemical pathways involving different enzymes (or enzyme systems). Clarifying the mechanism of stimulation of in vivo bioluminescence of higher fungi by caffeic acid is a priority for further research.

Ambipolar Charge Injection and Bright Light Emission in Hybrid Oxide/Polymer Transistors Doped with Poly(9‐Vinylcarbazole) Based Polyelectrolytes

AbstractLight‐emitting transistors (LETs) are a remarkable, emerging class of electronic devices that combine the switching function of field‐effect transistors (FETs) and the light‐emitting function of light‐emitting diodes (LEDs). In order to achieve efficient light emission, effective electron and hole injection from source and drain electrodes is necessary. Various strategies have been introduced to accomplish this, such as incorporating asymmetric electrodes or charge injection layers during device fabrication. These approaches have inevitably introduced complexity in the device fabrication process. Herein, light‐emitting electrochemical transistors (LECTs) are demonstrated that combine principles of electrochemistry and optoelectronics to achieve multi‐functionality in a simple device architecture. Hybrid polyelectrolytes, poly(9‐vinylcarbazolesulfonate)‐ lithium and copper (II) salts (PVK‐Li and PVK‐Cu) incorporating Li+ ion and Cu2+ ions are added at variable concentrations to the organic emitting layer of LECTs to effect electrochemical p‐type doping. This electrochemical doping approach yielded improvements in electrical and optical performances including mobilities, brightnesses, and external quantum efficiency of the LECTs. The dynamics of how charges including ions, electrons, and holes move and interact are discussed in the device to facilitate emissive charge carrier recombination and light emission. This investigation provides valuable insights into the realms of both electrochemistry and optoelectronics.

Multiphonon-coupling yellow laser in Yb:La2CaB10O19 crystal

Yellow lasers at 590 nm have many extensive applications in our daily life, but extremely difficult to attain by traditional solid-state laser technology, owing to the absence of highly-efficient transition channels at this spectral range. In this work, we proposed a cooperative lasing mechanism to obtain the yellow light emission, with multiphonon-assisted electronic transitions and phase-matched frequency-doubling. Based on the predictable configurational coordinate model, we can calculate the multiphonon-assisted emission step-by-step. Using Yb3+-doped La2CaB10O19 crystal as an example, it is capable of producing yellow laser at 581–590 nm, with a maximum output power of 4.83 W and a high slope efficiency of 31.6%. To the best of our knowledge, it represents the highest power of solid-state yellow laser realized in one single crystal pumped by a laser diode. This power scaling can be assigned to the amplified phonon-assisted emission beyond the fluorescence spectrum, and optimized crystal angle for phase-matching condition. Such a compact, low-cost, and high-power laser device, provides an alternative candidate for the spectral “yellow-gap” where no practical solid-state laser exists at present.

One-Pot Synthesis of Vinylogous Cyano Aminoaryls (VinCAs) as Benzenic Fluorophores: Tailoring Diverse Emission Colors for White Light Emitting Materials and Cell Imaging.

Donor-acceptor-based organic small molecules with an electronic push-pull effect can demonstrate intramolecular charge transfer to show interesting photoluminescence properties. This is an essential criterion for designing fluorogenic probes for cell imaging studies and the development of organic light-emitting diodes. Now, to design such optical materials sometimes it is necessary to tune the band gap by controlling the energies of the highest occupied molecular orbital and lowest unoccupied molecular orbital. Typically, the band gaps could be modulated by installing unsaturated handles between electron-rich donors and electron-deficient acceptors. However, these methods are often synthetically and economically challenging due to the involvement of expensive catalysts and difficult reaction setups. In our present study, we show a straightforward, cost-effective method for obtaining a series of donor-acceptor-type Vinylogous Cyano Aminoaryls (VinCAs) with diverse emission colors. Further studies reveal that these VinCAs can serve as effective cell imaging agents, showcasing potential use in chemical biology. Additionally, these molecules could be further used to generate white light emission (WLE), showing their potential utility in advanced lighting technologies.

Effects of Heavy p‐Block Elements on Photophysical Properties of π‐Conjugated Complexes and Organoelement Compounds

π‐Conjugated compounds exhibit remarkable photophysical properties, such as strong light absorption and emission, and are applicable to organic devices, bioimaging, and sensing systems. The introduction of p‐block elements into π‐conjugated systems is presumable as a critical strategy for modulating their properties. Nevertheless, the type of utilized elements has been limited to the second and third‐period ones because it is difficult to construct critical electronic interactions between heavier atoms and carbon‐based π‐conjugated scaffolds. On the other hand, it has been recently suggested that the heavier p‐block elements are able to induce significant changes in the optoelectronic properties of π‐conjugated systems thanks to their large size, high polarizability, and heavy atom effect. Although there are much room to explore effects of heavy‐atom substitution on physical and electronic properties of conjugated systems, various characters have been discovered. Hence, this review mainly focuses on the relationships between the types of p‐block elements and the optical properties of their representative complexes and organoelement compounds, particularly light absorption and emission.

Literature Review on Conjugated Polymers as Light-Sensitive Materials for Photovoltaic and Light-Emitting Devices in Photonic Biomaterial Applications

Due to their extended p-orbital delocalization, conjugated polymers absorb light in the range of visible–NIR frequencies. We attempt to exploit this property to create materials that compete with inorganic semiconductors in photovoltaic and light-emitting materials. Beyond competing for applications in photonic devices, organic conjugated compounds, polymers, and small molecules have also been extended to biomedical applications like phototherapy and biodetection. Recent research on conjugated polymers has focused on bioapplications based on the absorbed light energy conversions in electric impulses, chemical energy, heat, and light emission. In this review, we describe the working principles of those photonic devices that have been applied and researched in the field of biomaterials.

Fabrication Process of MicroLED Film for Achieving Vertical Current Injection Using Transfer Technology

Flexible light‐emitting devices have attracted attention as a novel bio‐interface connecting living tissues with electronics due to their high brightness, low power consumption, and durability in humid environments. Introduction of vertically current‐injected micro‐light‐emitting diodes (MicroLEDs) into this film can enhance the MicroLED effective area and improve device characteristics. In this study, the MicroLED transfer technology onto conductive materials is investigated. The feasibility of batch transferring MicroLEDs onto a conductive polymer is demonstrated by PEDOT:PSS layer. For non‐Ohmic characteristics between n‐GaN and PEDOT:PSS, a backside‐open MicroLED hollow structure is proposed, enabling the formation of Ti/Au electrodes on the backside of MicroLED. By transferring the fabricated vertically current‐injected MicroLEDs onto the PEDOT:PSS layer, a flexible vertically current‐injected LED film is achieved, observing uniform blue light emission. The developed MicroLED film holds promise as a new neuroscience tool for targeting specific areas of the brain with light.

Enhanced Spontaneous Light Emission of ZnO Nanowire-Based Gratings

Enhanced Spontaneous Light Emission of ZnO Nanowire-Based Gratings

Light Emission Characteristics in Nitride Semiconductor Nanowires Fabricated by Top‐down Method

Nanophotonic devices made from nitride semiconductors are promising for various applications, especially those utilizing ultraviolet‐visible light with low‐power consumption and high driving speed. Herein, nanowire structures are fabricated from a light‐emitting diode epitaxial wafer and demonstrates the effectiveness of wet etching in top‐down fabrication. Spontaneous emission from active layers and unanticipated lasing derived from a GaN layer in a single nanowire are observed by microphotoluminescence measurement. Lastly, the lasing mode through a 3D simulation of the eigenmodes in this nanowire structure is clarified.

Free Electron-Plasmon Coupling Strength and Near-Field Retrieval through Electron Energy-Dependent Cathodoluminescence Spectroscopy.

Tightly confined optical near fields in plasmonic nanostructures play a pivotal role in important applications ranging from optical sensing to light harvesting. Energetic electrons are ideally suited to probing optical near fields by collecting the resulting cathodoluminescence (CL) light emission. Intriguingly, the CL intensity is determined by the near-field profile along the electron propagation direction, but the retrieval of such field from measurements has remained elusive. Furthermore, the conditions for optimum electron near-field coupling in plasmonic systems are critically dependent on such field and remain experimentally unexplored. In this work, we use electron energy-dependent CL spectroscopy to study the tightly confined dipolar mode in plasmonic gold nanoparticles. By systematically studying gold nanoparticles with diameters in the range of 20-100 nm and electron energies from 4 to 30 keV, we determine how the coupling between swift electrons and the optical near fields depends on the energy of the incoming electron. The strongest coupling is achieved when the electron speed equals the mode phase velocity, meeting the so-called phase-matching condition. In aloof experiments, the measured data are well reproduced by electromagnetic simulations, which explain that larger particles and faster electrons favor a stronger electron near-field coupling. For penetrating electron trajectories, scattering at the particle produces severe corrections of the trajectory that defy existing theories based on the assumption of nonrecoil condition. Therefore, we develop a first-order recoil correction model that allows us to account for inelastic electron scattering, rendering better agreement with measured data. Finally, we consider the albedo of the particles and find that, to approach unity coupling, a highly confined electric field and very slow electrons are needed, both representing experimental challenges. Our findings explain how to reach unity-order coupling between free electrons and confined excitations, helping us understand fundamental aspects of light-matter interaction at the nanoscale.

A linearly polarized light emission with a composite nanowire grating in whole white band

To obtain a highly linearly polarized light, a composite model consisting of white light emission, anti-reflection film, and metal-dielectric-metal nanowire grating was designed, analyzed, optimized, and fabricated. Based on the finite-difference time-domain method, the impacts of material, period, height, and incidence angle on the polarization performance of the composite model were discussed. The metal-dielectric-metal nanowire grating was fabricated on blue chip and fluorescent ceramics using nanoimprint technology. The employed materials of metal-dielectric-metal nanowire grating were aluminum and PMMA, with the period of 200 nm, wire width of 100 nm, and the height of metal and dielectric were 100 nm and 120 nm. Additionally, the anti-reflection film consisting of PMMA with the thickness of 45 nm was incorporated on fluorescent ceramics to enhance energy efficiency. Finally, through a series of test experiments, the composite model can be realized by the extinction ratio of 40 dB, while the transmittance of TM mode exceeds 50% at 450–750 nm. The theoretical analysis of this study is verified by experiments, and it has significant potential in the pursuit of high brightness, ultra-thin micro displays.