Light Display Research Articles

The synthesis and luminescence properties of Bi3+/Eu3+ co-doped Gd2O3 phosphors with high thermal stability and tunable emission via energy transfer

In this work, the highly monodisperse (Gd0.99-xBi0.01Eux)2O3 phosphors with spherical morphologies (∼170 nm) are successfully obtained through precursor synthesis via urea-based homogeneous precipitation (UBHP) method, followed by annealing at 1000 °C. The Bi/Eu-doped does not alter the crystal structure, and maintain the cubic structure of the Gd2O3 host. Owing to the Bi3+ occupies two different sites (C2, S6) in Gd2O3 of the cubic phase, the 1S0 → 3P1 transition of Bi3+ has two significant excitation bands (335 nm and 375 nm). By monitoring the excitation at 335 nm and 375 nm, the (Gd0.99-xBi0.01Eux)2O3 phosphors show both Bi3+ (420 nm and 530 nm) and Eu3+ (611 nm) emissions, respectively. The presences of Gd3+ and Bi3+ excitation bands on the PLE spectra by monitoring the Eu3+ emission indicate the Bi3+ → Eu3+ and Gd3+ → Eu3+ energy transfer, respectively, and the energy transfer efficiency is up to 99 %. Meanwhile, the energy transfer mechanism of the (Gd0.99-xBi0.01Eux)2O3 samples is dominated by the dipole-dipole interaction. Under two different excitation wavelengths, the emission intensity varies with the Eu3+ doping content and the quenching concentration is about 3 at%. The calculated value of the critical distance Rc is 12.12 Å, which indicates that the quenching mechanism is mainly caused by the multipole interaction. Meanwhile, the emission color can be tuned though adjusting the Eu3+ content. The temperature-dependent (in the range of 100–500 K) analysis has been obtained, the results indicate the (Gd0.99-xBi0.01Eux)2O3 samples have good thermal stability. The (Gd0.99-xBi0.01Eux)2O3 phosphors developed in this work is expected to be widely used in lighting and optical display applications.

SISTEM MONITORING KETINGGIAN OMBAK AIR LAUT SECARA REAL-TIME BERBASIS IoT

Indonesia is an archipelagic country where most of its territory is water, so all activities carried out in water, especially the sea, are an important part of the life of the Indonesian people. The height of the sea waves is a phenomenon that greatly affects the efficiency and safety of people when they are in sea waters. The process of obtaining sea wave height data requires an appropriate system. So this study designed a prototype system for monitoring the height of sea waves in real-time based on IoT. The method used is the waterfall, where the ultrasonic sensor will be connected to the ESP-8266 nodemcu so that real-time sea wave height data is obtained through the user interface on the Thinger IO Platform. In addition, the system uses red, yellow, and green LEDs as indicators of the height of the water waves. These results indicate that the application of real-time IoT-based sea wave height systems has good capabilities. This is indicated by the user being able to see real-time monitoring data on sea wave height based on IoT with the display of numbers, graphs, and LED indicator lights. For the seawater level scale used in the system, the LED indicator lights in red are 0-10 cm,yellow are 11-20 cm, and green are 21-30 cm.

Study on the structure and optical properties of the Tb3+-doped SrO–MgO–SiO2–TiO2–B2O3 glasses

In this investigation, Tb3+-doped SrO–MgO–SiO2–TiO2–B2O3 glasses were prepared using the melting-cooling technique. The amorphous nature of the glass was confirmed through XRD analysis. The thermodynamic parameters of the glass were determined by DSC testing, and the crystallization activation energy was calculated. Using infrared spectroscopy, the network structure of the glass was investigated. At 376 nm excitation, the emission spectrum was obtained, which contained six emission bands: 415 nm (5D3→7F5), 437 nm (5D3→7F4), 489 nm (5D4→7F6), 545 nm (5D4→7F5), 586 nm (5D4→7F4) and 623 nm (5D4→7F3). With the increase of Tb2O3 ion-doping concentration, the emission intensity of the 5D3 excited state decreases gradually, while that of the 5D4 excited state increases gradually. Also measured were the lifetimes of Tb3+: 5D3 and 5D4 fluorescence decay. The luminescence of the glass falls within the green region of the CIE chromaticity coordinates, and the correlated color temperature index indicates that the luminescence is pale green. The results show that the Tb3+ doped SrO–MgO–SiO2–TiO2–B2O3 glasses system has a potential application prospect in the field of green light display.

High-Performance Hot-Exciton OLEDs via Fully Harvesting Triplet Excited States from Both the Exciplex Co-Host and the TBRb Emitter.

The high-level reverse intersystem crossing (HL-RISC, T2 → S1 ) process from triplet to singlet exciton, namely the "hot exciton" channel, has recently been demonstrated in the traditional fluorescent emitter of TBRb. Although it is a potential pathway to improve the utilization of non-radiative triplet exciton energy, highly efficient fluorescent organic light emitting diodes (FOLEDs) based on this "hot exciton" channel have not been developed. Herein, high-efficiency and low-efficiency roll-off FOLEDs are achieved through doping TBRb molecules into an energy-level matched exciplex co-host. Combining the low-level RISC (LL-RISC, EX3 → EX1 ) process in the exciplex co-host with the HL-RISC process of hot excitons in TBRb to fully harvest the triplet energy, a record-high external quantum efficiency (EQE) of 20.4% is obtained via a proper Dexter energy transfer of triplet excitons, realizing the efficiency breakthrough from fully fluorescent material-based OLEDs with TBRb as an end emitter. Furthermore, the fingerprint Magneto-electroluminescence (MEL) as a sensitive measuring tool is employed to visualize the "hot exciton" channel in TBRb, which also directly verifies the effective energy confinement and the full utilization of hot excitons. Obviously, this work paves a promising way for further fabricating high-efficiency TBRb-based FOLEDs for lighting and flat-panel display applications.

Large‐scale human celebrations increase global light pollution

Abstract Culturally dependent human social behaviours involving artificial light usage can potentially affect light pollution patterns and thereby impact the night‐time ecology in populated areas, although to date this has not been examined globally. By analysing continuous (monthly), highly resolved, spatially explicit data on global night lights (Visible and Infrared Imaging Radiometer Suite–Day/Night Band‐VIIRS‐DNB; 2014–2019) with circular statistical techniques, we evaluated whether macro‐cultural activities involving social aggregations and the use of artificial lights shape annual lighting patterns globally. Scheduled routines associated with cultural‐specific festivities appear to be important drivers of observed seasonal patterns in urban night‐time lights. For instance, the display of Christmas lights between Christmas and Epiphany Day celebrations (December–January) coincides with the annual peak in urban night‐time light intensity in Christian countries. Analogously, night celebrations during the Holy Month of Ramadam (from May to July) or the month‐long period of Karthika Masam (from October to November) fits with annual night light peaks in Muslim and Hindu countries. Annual peaks of urban light intensity in China and Vietnam also match with Chinese and Vietnamese (Tê't) New Year celebrations (January–February). In contrast, predominantly Buddhist countries, which do not have such prominent and prolonged celebrations involving artificial lights, show a relatively uniform distribution of night light peaks throughout the annual cycle. Social behaviour and sociocultural contexts help explain how people modify the global nightscape and contribute to light pollution globally. Understanding the cultural contexts responsible for peaks in artificial light usage is an important first step if humans are to mitigate any deleterious effects associated with global increases in night‐time light pollution. Read the free Plain Language Summary for this article on the Journal blog.

Helical Nanofiber Photoelectric Synaptic Devices for an Artificial Vision Nervous System.

Inspired by the helical structure and the resultant exquisite functions of biomolecules, helical polymers have received increasing attention. Here, a series of poly(3-hexylthiophene)-block-poly(phenyl isocyanide) (P3HT-b-PPI) copolymers were prepared using a simple one-pot living polymerization method. Interestingly, the P3HT80-b-PPI30 films were found to have a helical nanofiber structure. The corresponding device has superior optoelectronic properties, such as a broadened spectral response range from the visible band to the deep ultraviolet (DUV) and an approximately 5-fold longer carrier decay time after DUV light stimulation. An energy consumption of 1.44 fJ per synaptic event was obtained, which is the lowest energy consumption achieved so far with DUV light stimulation. The encryption and decryption of images are implemented using an array of devices. Finally, a photoreceptor neural pathway was constructed to achieve early warning for the recognition of the display of harmful light. This research provides an effective strategy for the development of a novel optoelectronic synaptic device.

Ultrastable emissive perovskite nanocomposite via dual protection of polymer-grafted TS-1 zeolite for backlight display application

Instability of all-inorganic perovskite quantum dots (PQDs) driven by the inherent ionic nature poses a grand challenge towards their long-term stability in optoelectronic devices. Herein, we report the crafting of a highly stable dual-protected CsPbBr3 perovskite nanocomposite by capitalizing on the encapsulation of a hydrophobic Styrene-Divinylbenzene (St-Dvb) copolymer grafted hierarchical titanium silicalite-1 (TS-1) zeolite shell. Firstly, an optimal hot injection method was used to accommodate CsPbBr3 PQDs into hierarchical TS-1 zeolite. After the modification of terminated Si-OH groups on the surface of TS-1 by phenyltriethoxysilane (PTES), a subsequent polymerization of St and Dvb was implemented using azobisisobutyronitrile (AIBN) as initiator to result in the highly emissive CsPbBr3-TS@St-Dvb nanocomposite, exhibiting outstanding luminescent stability against heat, polar solvents, and UV light irradiation. The as-prepared CsPbBr3-TS@St-Dvb nanocomposite also showed strongly suppressed anion exchange and high compatibility in polymer matrix, enabling improved applicability for versatile lighting and optical display applications. Ultimately, a white light-emitting diode (WLED) composed of green-emitting CsPbBr3-TS@St-Dvb and red-emitting K2SiF6:Mn4+ phosphor onto a commercial blue InGaN LED chip with wide color gamut and excellent stability is demonstrated. This work highlights a judiciously-designed and hard-soft dual-protected strategy to produce ultrastable perovskite nanomaterials with high brightness and durability for backlight display application.

Luminescence properties of Tb3+/Eu3+ ions activated LiLaSiO4 phosphors for solid-state lighting and flexible display applications

The synthesis and luminescence properties of Tb3+ and Eu3+ single- and co-doped LiLaSiO4 (LLSO) phosphors with energy transfer mechanisms were reported. The rare-earth ions doped LLSO phosphors were synthesized via a solid-state reaction method and their physical characterizations such as phase purity, surface morphology, and elemental analysis were investigated systematically. For the Tb3+ and Eu3+ single- and co-doped LLSO phosphors, their photoluminescence (PL) properties were studied in detail. The LLSO:Tb3+ and LLSO:Eu3+ single-doped phosphors showed superior red and green emissions due to 5D4→7F5 and 5D0→7F2 in the optimized characteristic electronic transitions under ultraviolet (UV) irradiation, respectively. The luminescence performances for both the LLSO:Tb3+ and LLSO:Eu3+ phosphors were optimized at 0.125 mol of doping ion concentration. Under UV excitation, by adjusting the Eu3+ ion concentration in LLSO:0.125Tb3+/Eu3+ phosphors, the tunable emissions from green to red via yellow-orange were obtained. Thus, the tunable emission spectra and luminescence decay lifetimes with increasing the doping content of acceptor ions (Eu3+) confirmed an efficient energy transfer from Tb3+ to Eu3+ ions in the co-doped samples. The critical distance between Tb3+ and Eu3+ was determined to be 13.26 Å and the energy transfer mechanism from Tb3+ to Eu3+ ions was demonstrated to be a dipole-dipole mechanism interaction. In addition, the temperature-dependent PL study was carried out for the LLSO:0.125Tb3+/0.025Eu3+ co-doped phosphor sample and it showed better thermal stability against the temperature quenching. The Tb3+ and Eu3+ single- and co-doped LLSO/polydimethylsiloxane (PDMS) flexible composite films were fabricated by mixing the phosphor powders and PDMS solution. Benefiting from the effective protection of the PDMS matrix, the luminescence stability of the composite films was greatly enhanced. Based on the excellent properties of the synthesized phosphors, Tb3+ and Eu3+ single-doped and Tb3+/Eu3+ co-doped LLSO phosphors could serve as a single-phase multicolor-emitting phosphor under UV excitations.

36‐3: Design and Analysis of Brightness enhancement Integral Imaging Based 3D Light‐Field Normal Display and Optical See‐Through Light‐Field Display by Discrete Lenslet Array

We want to create a floating projection with integral imaging based 3D light field normal display and with an optical see‐through display. Using the Computer Generated Elemental Image (CGEI) method to create an image with a different depth from a two‐dimensional image and depth map. We create a new weight function instead of using the previous one from the previous paper in the same method. Also, creating an optical see‐through light‐field display by using a discrete lenslet array. Finally, we created naked 3D with brighter information and realize floating projection effect with a see‐through display.

Azaborine as a Versatile Weak Donor for Thermally Activated Delayed Fluorescence

Extensive research has been devoted to the development of thermally activated delayed fluorescence emitters, especially those showing pure-blue emission for use in lighting and full-color display applications. Toward that goal, herein we report a novel weak donor, 1,4-azaborine (AZB), with complementary electronic and structural properties compared to the widely used dimethylacridan (DMAC) or carbazole (Cz) donors. Coupled with a triazine acceptor, AZB-Ph-TRZ is the direct structural analogue of the high-performance and well-studied green TADF emitter DMAC-TRZ and has ΔEST = 0.39 eV, a photoluminescence quantum yield (ΦPL) of 27%, and λPL = 415 nm in 10 wt % doped mCP films. The shortened analogue AZB-TRZ possesses red-shifted emission with a reduced singlet-triplet gap (ΔEST = 0.01 eV) and fast reverse intersystem crossing (kRISC of 5 × 106 s-1) in mCP. Despite a moderate ΦPL of 34%, OLEDs with AZB-TRZ in mCP showed sky-blue emission with CIE1931(x,y) of (0.22,0.39) and a maximum external quantum efficiency (EQEmax) of 10.5%. Expanding the chemist's toolkit for the design of blue donor-acceptor TADF materials will enable yet further advances in the future, as AZB is paired with a wider range of acceptor groups.

Counting All Photons: Efficient Optimization of Visible Light 3D Printing

AbstractThe utility of visible light for 3D printing has increased in recent years owing to its accessibility and reduced materials interactions, such as scattering and absorption/degradation, relative to traditional UV light‐based processes. However, photosystems that react efficiently with visible light often require multiple molecular components and have strong and diverse absorption profiles, increasing the complexity of formulation and printing optimization. Herein, a streamlined method to select and optimize visible light 3D printing conditions is described. First, green light liquid crystal display (LCD) 3D printing using a novel resin is optimized through traditional empirical methods, which involves resin component selection, spectroscopic characterization, time‐intensive 3D printing under several different conditions, and measurements of dimensional accuracy for each printed object. Subsequent analytical quantification of dynamic photon absorption during green light polymerizations unveils relationships to cure depth that enables facile resin and 3D printing optimization using a model that is a modification to the Jacob's equation traditionally used for stereolithographic 3D printing. The approach and model are then validated using a distinct green light‐activated resin for two types of projection‐based 3D printing.

On-chip optical sources of 3D photonic integration based on active fluorescent polymer waveguide microdisks for light display application

In this work, on-chip three-dimensional (3D) photonic integrated optical sources based on active fluorescent polymer waveguide microdisks are proposed for light display application. Fluorescent green and red oligomers with high-efficiency photoluminescence are doped into epoxy crosslinking SU-8 polymer as the waveguide gain medium. The microdisk-based on-chip optically pumping light sources are designed and fabricated using the organic functionalized materials by direct UV written process. The promising stacking dual-microdisk structures with double gain layers could provide white signal light source generated perpendicular to the chip, and green signal light source stimulated in the chip. The approach could realize the monolithically on-chip assembled vertical and horizontal bright emitters. The optical pumping threshold power is obtained as 50 mW with continuous-wave (CW) pumping. The average gain coefficient of a white light source is measured by vertical fiber coupling as 112 dB/W, and that of green light source by horizontal fiber coupling as 137 dB/W, respectively. The rising and falling response time of the on-chip optical sources are 60 and 80 µs under modulating pulsed pumping. This technique is very promising for achieving 3D integrated light display application, including photonic circuits and optical information encryption.

PROTOTYPE OF ARDUINO-BASED WATER LEVEL DETECTOR WITH ULTRASONIC SENSOR

Most of the water can be found in the sea (salt water) and in the ice caps (at the poles and on the tops of mountains). Apart from that, water can also be found in clouds, rain, rivers, surface fresh water, lakes, water vapor, and sea ice. The water in these objects moves according to a water cycle, namely: through evaporation, rain, and the flow of water over the ground surface (runoff, including springs, rivers, estuaries) towards the sea. Floods are natural disaster events that occur when an excessive flow of water submerges land. Floods can occur within minutes or over a long period of time, and can last days, weeks, or longer. Floods are the most common and widespread of all weather-related natural disasters. The tool can function properly. The height can be set to be displayed with an LED light display. Can be applied to the floodgates to activate the motor driving the floodgates so that the water level through the floodgates can be adjusted in such a way.

ID Asks/Kenneth Werner

ID Asks/Kenneth Werner

Exploring Multiple Strategies towards Luminescent Fibers and Applications

Since its invention, luminous fibers have received extensive attention from scientific researchers. Luminous fibers are mainly distinguished by their energy source and are divided into two types active and passive luminous. As an emerging fiber material, luminescent fibers have been used in the military, firefighting, marine transportation, fishing, and other fields; mainly covering the application of each luminescent fiber fabric, light display materials, luminescent fiber components, energy conversion components, intelligent textiles, anti-counterfeit labels, unique clothing, etc. This paper introduces the classification and luminescence principle of luminescent fibers around the research progress of luminescent fibers in recent years and outlines the relevant applications of luminescent fibers.

Dual-wavelength hologram of high transmittance metasurface.

In this work, a simple dielectric metasurface hologram is proposed and designed by combining the electromagnetic vector analysis method and the immune algorithm, which can realize the holographic display of dual wavelength orthogonal-linear polarization light in visible light band, solve the problem of low efficiency of the traditional design method of metasurface hologram, and effectively improve the diffraction efficiency of metasurface hologram. The titanium dioxide metasurface nanorod based on rectangular structure is optimized and designed. When the x-linear polarized light with wavelength of 532 nm and y-linear polarized light with wavelength of 633 nm are incident on the metasurface respectively, different display output images with low cross-talk can be obtained on the same observation plane, and the transmission efficiencies of x-linear and y-linear polarized light are as high as 68.2% and 74.6% respectively in simulation. Then the metasurface is fabricated by Atomic Layer Deposition method. The experimental results are consistent with the design results, which proves that the metasurface hologram designed by this method can completely realize the feasibility of wavelength and polarization multiplexing holographic display, and has potential application value in holographic display, optical encryption, anti-counterfeiting, data storage and other fields.

Time-multiplexed vector light field display with intertwined views via metagrating matrix

Three-dimensional (3D) display is the future technology of display. The insufficient refreshable information provided by the screen is one of the major bottlenecks that hinders the development of light field 3D display. In this paper, a time-multiplexed vector light field display is proposed to increase the amount of information by exploiting the time redundancy. A view modulator with fully coverage of metagrating matrix is adopted to generate two groups of time-sequentially lit-up intertwined views. With a small deflection angle of incidence, the intertwined-view based time-multiplexing strategy is beneficial because of the less stray light and crosstalk, compared with the successively arranged views. Therefore, the system volume and complexity of directional backlight are reduced. In the experimental demonstration, a time-multiplexed vector light field 3D display is constructed with 18 views. The horizontal field of view reaches 51°. The potential applications include human-computer interaction, commercial exhibition, and medical hygiene.

Tunable Emission Wavelength and Chromaticity Electroluminescence Realized in Ho Doped ZnO Microspheres Heterojunction

Tunable white light sources have huge potential applications in the scope of intelligent lighting or high-quality display system, but it is still a challenge to tune the emission wavelength and chromaticity in a simple structure. Herein, the Ho3+ doped ZnO microsphere was bonded onto the p-GaN substrate to form a heterojunctional light-emitting diode. Through a combination of the light confinement effect in the ZnO microsphere and multilevel emission system in rare earth materials, the device demonstrates tunable electroluminescence (EL) both in wavelength and chromaticity. The device shows broadband emission peak at 400 nm with full width at half maximum (FWHM) of 34 nm under forward pulsed driven bias. While it shows a series of sharp emissions from rare earth ions Ho3+ with peaks at 427 nm, 492 nm, 567 nm, 592 nm and 654 nm and FWHM less than 1.3 nm under reverse pulsed driven bias. More meaningful, the wavelength and chromaticity can be controlled with duty cycle or the rate of forward and reverse driven bias under intelligent programmable alternating current (AC) driven. Finally, the gradient from blueviolet light to white light can be realized.

Metal halide perovskite nanocrystal with fluorescence enhancement in wet and acidic environment

Metal halide perovskite nanocrystals have excellent prospects in solid-state lighting, flexible display, sensing, and other optoelectronic applications due to their superb photoelectric properties (high quantum efficiency and fast carrier diffusion speed). However, they are susceptible to environmental factors such as ultraviolet radiation and polar solvents. Especially in a water environment, poor stability seriously restricts the application of perovskite optical devices. In this paper, a kind of porous polymer (ethylene-vinyl acetate copolymer, EVA) and perovskite nanocrystals were mixed to form perovskite nanocrystals-EVA composites. The obtained composites were aged in water for 21 days, and the fluorescence enhancement was 170 times. Even in a strongly acidic environment, the fluorescence enhancement was 91 times. The information encryption mode of the composite material can effectively encrypt information in a wet environment due to the change of light wavelength, making a white light-emitting diode (w-LED). This metal halide perovskite nanocrystals-EVA composite will unleash a wide variety of solid-state lighting and flexible display possibilities that are limited by the use of existing methods in humid and strongly acidic environments.

Organic Charge‐Transfer Complexes for Near‐Infrared‐Triggered Photothermal Materials

Organic photothermal materials excited by near‐infrared (NIR) light display promising applications in biomedicine, optoelectronic devices, water purification, and so on. However, the most NIR responsive organic photothermal materials are in the mire of laborious synthesis, high cost, and limited functions. The newly emerging charge‐transfer complexes (CTCs) are promising photothermal materials to solve the issues and are receiving much attention. Compared with traditional photothermal agents, CTCs possess strong NIR absorption, high photo‐to‐thermal conversion efficiency, simple synthesis, and function‐directed material design. Herein, the latest advances in NIR‐excited CTCs for photothermal agents are systematically summarized. First, the basic structure–performance relationships are introduced. Then, several important factors affecting the photothermal properties of the CTCs are discussed from the sight of photophysics, and a comprehensive comparison is made among the nanoparticle systems. Finally, organic photothermal CTCs are highlighted as a multifunctional platform for applications and the perspective is given.