Maximum Luminous Intensity Research Articles

A high toughness hydrogel with Dy3+ enhanced fluorescence properties: For visual Zn2+ detection

Rapid, portable, and sensitive detection of Zn2+ is crucial for human health. In this study, SA/PEG/Ln fluorescent hydrogels were synthesized via in situ polymerization with lanthanide metals (Tb3+/Dy3+) and PAM. The results demonstrated a significant improvement in mechanical properties (132.8 % increase in compressive properties) after rare earth doping. The addition of Dy3+ enhanced the fluorescence properties of the singly doped Tb3+ fluorescent hydrogel (maximum luminous intensity increased by 1900 cd). Monitoring changes in fluorescence intensity enabled the realization of Zn2+ detection, allowing for quick and accurate determination of zinc ion presence. Visual monitoring of Zn2+ was achieved with the assistance of a portable ultraviolet lamp.

From structure to luminescence investigation of B2O3-GeO2-BaO-ZnO glass doped with Dy3+

This study describes the preparation of Dy3+ doped B2O3-GeO2-BaO-ZnO (BGBZ) glass using a high temperature melting technique. By means of excitation and emission spectroscopy, it was determined that the glass sample with 25 mol% BaO content had the maximum luminous intensity. The internal structure of the glass was investigated using FT-IR spectroscopy, absorption spectrum testing, and J-O theoretical analysis in order to investigate the principle. The FT-IR spectrum revealed the coexistence of [BO3], [BO4], [GeO4], and [GeO6] coordination polyhedra. The Ω2 value reaching its maximum when the BaO content reached 25mol%, indicating the highest degree of asymmetry in the glass structure at that time. After analyzing the impact of BaO content on the glass structure, it was investigated how the concentration of Dy2O3 doping affected the glass's optical characteristics and radiation performance. By calculating the CIE of glass samples, it was found that the CCT value of glass sample 1.25Dy was 6735 K, suggesting that the produced glass may find use in the w-LED commercial industry. The 0.50Dy glass sample was calculated to have a high σse (8.47×10−22 cm2) from the emission spectral data, suggesting that the prepared glass sample may also be suitable for lasers.

Dual-mode luminescence light intensity modulation characteristics and optical radiation dependence of stannate photochromic ceramics

Alkaline earth stannate is characterized by good physicochemical stability. It has been applied in the field of optical information storage by coupling photoluminescence intensity modulation and photochromic performance, which has attracted the attention of researchers. The development of alkaline earth stannate ceramics with high light intensity modulation properties and non-destructive reading of optical information is of great research value. In this study, Er3+-doped Ca2SnO4 photochromic ceramics were prepared by high-temperature solid-phase reaction method. Alternating UV light irradiation and thermal stimulation, the ceramics achieve a reversible transition between light and dark gray. Er3+ doping gives the ceramics dual-mode luminescence light intensity modulation performance. When the doping amount of Er3+ is 0.01 mol, there is a maximum down-conversion luminous intensity modulation ratio of 93%, which is higher than most of the same type of photochromic materials. The photochromic behavior is explained using the capture-release model of traps for carriers, and the dual-mode luminescence light-intensity modulation behavior is analyzed through the energy transfer mechanism. The optical radiation response properties were investigated and the optimum light response wavelength is found to be 290 nm, which is related to the optical band gap Eg. And the selection of the optimal light response wavelength can effectively improve the performance of photochromic and light intensity modulation. This study provides a promising strategy for performance enhancement of photochromic materials.

Enhanced performance of solution processed OLED devices based on PFO induced TADF emission layers

The internal quantum efficiency (IQE) of the OLED devices based on thermally activated delayed fluorescence (TADF) materials was thought to nearly 100 % by assuming the light outcoupling efficiency of 20–25 %. However, the external quantum efficiency (EQE) is still limited by the ηout. One crucial factor that affects the light output coupling efficiency is the molecular transition dipole moment of the emission molecule. In this study, poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) was chosen as an orientation inducer to enhance the horizontal orientation ratio of a TADF emitter, 2-Phenyl-4,6-bis[4-(9,9-dimethyl-9,10-dihydroacridine) phenyl] pyrimidine (DMAc-PPM), prepared using a solution method. With doping PFO in weight ratios ranging from 1 wt% to 9 wt%, the orientation factor of TADF emitter increased, which testified the inducing function of PFO. The TADF-OLED devices using PFO as an inducer exhibited an EQE increasing with the PFO doping weight ratio. The maximum EQE of 7.3 % was achieved at the doping weight ratio of 7 wt%, which increase about 1.7 times compared to the device without the PFO inducer. This observed variation of EQE differs from the trend observed in maximum luminance intensity. The increase of EQE can be attributed to the improvement of light output efficiency caused by the variation of orientation factor. The lower carrier mobility lead to the lower maximum luminance intensity. The synergistic effect of light output efficiency and carrier mobility enhanced the performance of OLED devices.

High brightness blue electroluminescence of diamond/TmF3/LiF/TmF3 composite film

Although GaN-based blue light materials have been widely used in the field of optoelectronics, due to the high cost of preparation, and the emission wavelength of GaN-based devices will be easily affected by temperature and other external environment. Therefore, the development of other types of blue EL devices becomes another important option. In this paper, diamond/TmF3 composite film (DTCF) and diamond/TmF3/LiF/TmF3 composite film (DTLTCF) electroluminescent (EL) devices were fabricated on highly doped p-type silicon substrates. And experimental results show that the EL spectrum of DTCF device shows three peaks appear at 416 nm, 456 nm and 676 nm, while the EL spectrum of DTLTCF device only exhibits two strong peaks at 416 nm and 456 nm in the blue region. At the same time, the maximum luminous intensity of DTLTCF device is 2.5 times that of DTCF device, and the brightness can reach 25 cd/m2. The luminescence mechanism of DTCF and DTLTCF devices is discussed, and the mechanism of enhancing blue light emission and inhibiting red light emission by LiF layer is explained reasonably.

ZnO/silica quasi core/shell nanoparticles as electron transport materials for high-performance quantum-dot light-emitting diodes

Quantum dot light-emitting diodes (QLEDs) are considered as the ideal candidate for next-generation displays, solid-state lighting, and optical communication applications. Although the efficiency of QLEDs has been significantly improved to the level comparable to that of organic light-emitting diodes in recent years, simultaneously achieving high efficiency and high brightness still remains challenging for QLEDs. In this work, we report a facile and effective electron-transport-layer interface control strategy of incorporating 3-aminopropyl triethoxysilane (APTES) into a ZnO nanocrystal-solution to enhance charge injection balance and suppress interfacial exciton quenching via in-situ formation of ZnO/organic silica (hereinafter referred to as ZnO/SiO2) quasi core/shell nanoparticles in the solution, enabling red QLEDs to exhibit a maximum luminance intensity of 261,700 cd m−2, a peak external quantum efficiency (EQE) of 19.0%, and low efficiency roll-off at high luminance (an EQE up to 16.8% remained at a brightness of 200, 000 cd m−2). Our results demonstrate that substituting quasi core/shell-structured ZnO/SiO2 nanoparticles for traditional ZnO nanocrystals as electron transport materials is a simple and effective means of fabricating QLEDs with both high efficiency and high luminance, which is expected to facilitate the development of QLED technology toward practical applications in lighting, displays and optical communication.

Experimental optimization design synthesis and up-conversion luminescence properties of YNbO4:Ho3+/Yb3+

In order to obtain the maximum green up-conversion luminescence intensity of Ho3+/Yb3+ co-doped YNbO4, a uniform design and a quadratic general rotation combination design were applied to optimize the doping concentration. The concentration of the rare earth corresponding to the strongest green luminescence intensity was determined to be 10% Ho3+/34.9% Yb3+. Maximum luminous intensity of green light tested under 980 nm excitation was 157373.266, which was close to the theoretical calculated integral intensity value of 157290.825. The variation of the up-conversion luminescence spectra at different power density of the 980 nm laser was characterized. According to the formula fitting, the up-conversion luminescence process is a two-photon process. Meanwhile, the temperature sensing characteristic of the samples has been discussed. Finally, the CIE coordinates were analyzed and calculated to be (0.297, 0.692).

Up-Conversion Photoluminescence in Thulia and Ytterbia Co-Doped Yttria-Stabilized Zirconia Single Crystals

ZrO2 is an attractive host matrix for luminescence material because of its excellent physical properties, such as low phonon energy and wide band gap. In this work, the highly transparent Tm2O3 and Yb2O3 co-doped yttria stabilized zirconia (YSZ) (abbreviated as Yb/Tm: YSZ) single crystals were grown by the optical floating zone method. The Yb/Tm: YSZ samples were stabilized in the cubic phase at room temperature when Yb3+ and Tm3+ replaced Y3+. The influence of Yb3+ co-doping on the up-conversion luminescence properties of the crystals was systematically studied. A total of 0.5 mol% Tm2O3 and 2.0 mol% Yb2O3 co-activated YSZ single crystal (abbreviated as 2.0Yb/Tm: YSZ) has the maximum luminous intensity. There were seven absorption peaks located at around 358, 460, 679, 783.3, 850–1000, 1200, and 1721.5 nm that were observed in the absorption spectrum of the 2.0Yb/Tm: YSZ single crystal. There were three up-conversion peaks at around 488, 658 and 800 nm that were observed when the Yb/Tm: YSZ samples were excitated at 980 nm. The fluorescence lifetime of Tm3+ for the 1G4→3H6 transition of the 2.0Yb/Tm: YSZ sample is 7.716 ms as excited with a 980 nm laser. In addition, the oscillator strength parameters Ωλ (λ = 2, 4 and 6) of this sample were derived by the Judd–Ofelt theory to evaluate the laser performance of the host materials. The ratio Ω4/Ω6 of this sample is 0.80, implying its excellent laser output. Therefore, the 2.0Yb/Tm: YSZ single crystal is a considerable potential material for laser and luminescence applications.

Enhanced performance of organic light-emitting diodes by integrating quasi-periodic micro-nano structures

To integrate a quasi-periodic micro-nano structure (PMS) to the organic light-emitting devices (OLEDs) is an efficient way to enhance the performance of OLEDs. In this paper, the PMS prepared by the phase separation of Polystyrene and Poly (methyl methacrylate) was integrated to the OLEDs with the structures of Glass/PMS/Ag (30 nm)/MoO3 (5 nm)/(NPB) (40 nm)/(Alq3) (60 nm)/LiF (0.5 nm)/Al (150 nm). The maximum luminance intensity and external quantum efficiency increased to 10700 cd/m2 and 1.11 %, which is 48 % and 44 % higher than that of 7209 cd/m2 and 0.77 % of the planar reference device. The enhanced performance of OLEDs was ascribed to the attenuation of surface plasmon polariton loss caused by the PMS, which was testified by the Finite-Difference Time-Domain (FDTD) simulation. The PMS was also transferred to the hole transfer layer (PEDOT: PSS) of OLEDs by nano-imprinting lithography with the structure of Glass/(ITO) (100 nm)/PEDOT: PSS (100 nm) (with PMS)/NPB (10 nm)/Alq3 (50 nm)/LiF (0.5 nm)/Al (100 nm). The performance was also improved by the optimized PMS and the light out-coupling efficiency increased to about 49.5 %, which is much higher than that of 28.8 % in the OLEDs with PMS Ag anode and 20 % in the planar reference devices. This suggests that the PMS can improve the OLED device performance regardless of the functional layer in which the PMS is integrated.

LiF film enhanced high brightness blue electroluminescence of diamond /CeF3 composite film

Diamond/CeF3 composite film (DCCF) and diamond/CeF3/LiF composite film (DCLCF) electroluminescent(EL)devices were deposited on n-type heavy-doped silicon substrates by using microwave plasma chemical vapor deposition system (MPCVD) and vacuum electron beam vapor deposition system (EBVD). A series of corresponding tests characterized the composition, microstructure, and EL characteristics of the devices. The experimental results show that the LiF layer can effectively enhance the blue light emission intensity of the composite film device. Blue light emission can be observed in the two types of devices when the forward bias is applied, and the EL spectra of both devices show a strong wide peak at 440 nm. Meanwhile there is no significant difference in the maximum luminous intensity between them. However, when the reverse bias voltage is applied to the two devices, it is found that DCCF device hardly observes visible light emission, while the blue light emission of DCLCF device is very strong. And the EL spectrum of DCLCF device still shows a strong wide peak at 440 nm, and the blue light emission can reach the maximum at 350 V reverse bias voltage. Its maximum luminous intensity is 3.5 times that of DCCF devices, and its brightness can reach 35 cd/m2.

Aluminum‐Doped ZnO Weld Silver Nanowires‐Based High Transmittance, Low Sheet Resistance, and Tough Composite Transparent Conductive Films

Herein, silver nanowires (AgNWs) and aluminum‐doped zinc oxide (AZO) are prepared by polyol and gel–sol method, respectively. Then bendable, strong adhesion, flat, and high optical transmittance AgNWs:AZO composite transparent conductive film (TCF) is prepared in an all‐solution method. By spinning the AZO to the upper layer of the AgNW networks and annealing at 120 °C for 20 min, the junctions of the AgNW networks are welded by the capillary force in the solvent evaporation and AZO crystallization process. The sheet resistance of the TCF is as low as 12.9 Ω sq−1 at an optical transmittance of 92.1% (@550 nm), which is comparable to the indium tin oxide film on glass. The root means square roughness is reduced from 30.1 to 8.48 nm to match the criteria as anode for organic light emitting diodes (OLEDs). Furthermore, the adhesion between the AgNW networks and the substrate has been significantly improved. Finally, a flexible green OLED device with AgNW:AZO TCF as the anode is successfully prepared. The maximum luminous intensity of the prepared OLED is 10 060 cd m−2, and the maximum current efficiency is 6.43 cd A−1, which proves the great potential of the film in flexible electronics.

Continuous production of K2SiF6:Mn4+ red phosphor by green route synthesis method for warm WLEDs application

The K2SiF6:Mn4+ red phosphor has caused widespread concern in warm white light-emitting diodes (WLEDs) due to its unique broadband blue light absorption and narrow-band red emission. However, commercial K2SiF6:Mn4+ red phosphor inevitably needs to use extremely corrosive HF as a raw material, which will cause great harm to the environment and human beings. In this work, the K2SiF6:Mn4+ phosphor with highly uniform particle shape and size was successfully synthesized without using HF solution through microfluidic technology. The structure, morphology and photoluminescence properties of the K2SiF6:Mn4+ phosphors prepared in this work were systematically investigated and analyzed. The K2SiF6:Mn4+ phosphors synthesized by microfluidic technology are all cubic particles. The sample was the most uniform with a particle size of about 4.14 μm when the pipe diameter was 4 mm and the injection speed was 1000 μL/min, and the number of active Mn4+ in this sample is the largest according to the calculation results, resulting in its maximum luminous intensity. Finally, a warm WLED with low CCT (3379 K) and high CRI (Ra = 89.7) was fabricated by combining the as-prepared red K2SiF6:Mn4+ phosphor with yellow phosphor YAG:Ce3+ and blue LED chip. The results indicate that the K2SiF6:Mn4+ phosphor prepared by the proposed green continuous route is suitable for WLEDs.

Design and optical performance research of a fully customizable collimating lens based on total internal reflection.

An optical design method of a fully customizable collimating lens is proposed. The initial model of the complete lens is constructed by two parts. One part is calculated by the total internal reflection algorithm; the other part is constructed by trial-and-error method. The lens is further optimized by normal vector correction and high- and low-angle compensation. The optical performance of the fully customizable collimating lens is studied. It is proven to have good collimation performance with a divergence angle of 1.8° at 50% of the maximum luminous intensity; the uniformity is as high as 98.4%.

Спектральные характеристики и перенос энергии Ce-=SUP=-3+-=/SUP=-->Tb-=SUP=-3+-=/SUP=-->Eu-=SUP=-3+-=/SUP=- в соединении LuBO-=SUB=-3-=/SUB=-(Ce, Tb, Eu)

The structure, IR, luminescence, and luminescence excitation spectra of Ce3+, Tb3+, and Eu3+ ions in Lu1−2xCexEuхBO3 and Lu0.91−2xCexTb0.09EuхBO3 solid solutions were studied. The minimum "threshold" distance between Ce3+ and Eu3+ ions was estimated, at which there is no charge transfer between these ions, leading to the quenching of Ce3+ and Eu3+ luminescence. It is shown that in Lu0.91−2xCexTb0.09EuхBO3 compounds, the range of Ce and Eu concentrations of 0.2 – 0.25 at. % is optimal for obtaining the maximum luminous intensity of this compound.

Spectral characteristics and energy transfer Ce-=SUP=-3+-=/SUP=-->Tb-=SUP=-3+-=/SUP=-->Eu-=SUP=-3+-=/SUP=- in LuBO-=SUB=-3-=/SUB=-(Ce, Tb, Eu) compound

The structure, IR, luminescence, and luminescence excitation spectra of Ce3+, Tb3+, and Eu3+ ions in Lu1-2xCexEuxBO3 and Lu0.91-2xCexTb0.09EuxBO3 solid solutions were studied. The minimum "threshold" distance between Ce3+ and Eu3+ ions was estimated, at which there is no charge transfer between these ions, leading to the quenching of Ce3+ and Eu3+ luminescence. It is shown that in Lu0.91-2xCexTb0.09EuxBO3 compounds, the range of Ce and Eu concentrations of 0.2-0.25 at.% is optimal for obtaining the maximum luminous intensity of this compound. Keywords: phosphors for LEDs, rare earth orthoborates, X-ray diffraction analysis, IR spectroscopy, luminescence spectra.

High-Speed Fabrication of All-Inkjet-Printed Organometallic Halide Perovskite Light-Emitting Diodes on Elastic Substrates.

Halide perovskites have great potential for use in high-performance light-emitting diodes (LEDs) and displays. Here, a perovskite LEDs (PeLEDs) fabricated directly on an elastomer substrate, in which every single layer in the device from bottom anode to top cathode is patterned solely using a highly scalable inkjet printing process, is reported. Compared to PeLEDs made using conventional microfabrication processes, the printing process significantly shortens the fabrication time by at least tenfold (from over 5 h to less than 25 min). The all-printed PeLEDs have a novel 4-layer structure (bottom electrode, perovskite emissive layer, buffer layer, top electrode) without separate electron or hole transporting layers. For flexible PeLEDs printed directly in ambient conditions, a turn-on voltage, maximum luminance intensity, and maximum current efficiency of 3.46V, 10227cdm-2 , and 2.01cdA-1 , respectively, is achieved. The devices also exhibit excellent robustness and stability even when bent to a curvature radius of 2.5mm. The reported device structure and fabrication processes can enable high-performance flexible PeLEDs to be manufactured over a larger area at extremely low cost and fast speed, which can facilitate the adoption of the promising PeLED technology in the emerging foldable displays, smart wearables, and many other applications.

Highly Emissive 9-Borafluorene Derivatives: Synthesis, Photophysical Properties and Device Fabrication.

A series of 9‐borafluorene derivatives, functionalised with electron‐donating groups, have been prepared. Some of these 9‐borafluorene compounds exhibit strong yellowish emission in solution and in the solid state with relatively high quantum yields (up to 73.6 % for FMesB‐Cz as a neat film). The results suggest that the highly twisted donor groups suppress charge transfer, but the intrinsic photophysical properties of the 9‐borafluorene systems remain. The new compounds showed enhanced stability towards the atmosphere, and exhibited excellent thermal stability, revealing their potential for application in materials science. Organic light‐emitting diode (OLED) devices were fabricated with two of the highly emissive compounds, and they exhibited strong yellow‐greenish electroluminescence, with a maximum luminance intensity of >22 000 cd m−2. These are the first two examples of 9‐borafluorene derivatives being used as light‐emitting materials in OLED devices, and they have enabled us to achieve a balance between maintaining their intrinsic properties while improving their stability.

Synthesis and Fabrication of Fluorescent Green OLEDs Based on PEDOT:PSS/Silver Nanowire Hybrid-Composite Anode and Their Performance

Transparent conducting films have attracted increasing attention for their usefulness in optoelectronic devices, such as solar cells, liquid crystal display, and LEDs. Silver nanowires (AgNWs) with a length of 20 μm and a diameter of 70 nm was synthesized using polyol process. The optimized concentration of AgNWs is 0.5 mg of Ag NWs in 1 ml of PEDOT:PSS and it was used to fabricate PEDOT:PSS/AgNWs hybrid-composite TCF electrode, resulting in 88% transmittance and good electrical conductive (30 Ω sq−1) thin film. Two types of green fluorescent OLEDs were fabricated: those made with conventional ITO anode and the anode based on PEDOT:PSS/Ag NWs hybrid-composite. The observed maximum luminous intensity was increased by 27% in OLED fabricated PEDOT:PSS/AgNWs hybrid-composite TCF electrode, compared to the conventional ITO. At a wavelength of 530 nm, the maximum luminous intensities for green fluorescent OLEDs fabricated on PEDOT:PSS/AgNWs hybrid-composite TCF and ITO anode were 1610 counts per second and 1260 counts per second, respectively. The observed maximum current density increased by 28% as compared to the conventional ITO. The observed current densities were 370 mA cm−2 for OLEDs fabricated on PEDOT:PSS/AgNWs hybrid-composite TCF-based anode, and 293 mA cm−2 for conventional ITO anode. The proposed hybrid-composite electrode is a suitable material to replace conventional ITO.

Investigation of structure and luminescence properties of Tb3+ activated Gd(Ta1−xPx)O4 phosphors

Gd(Ta1−xPx)O4: y at.% Tb3+ phosphors with various doping concentrations of (PO4)3− and Tb3+ were prepared through high temperature solid-state method, and the corresponding crystal structures and luminescence properties were explored. XRD results indicate single phase M-Gd (Ta1-xPx) O4 can be obtained with 1300 °C sintering conditions without phase transformation. The optimized doping concentration for (PO4)3−and(TaO4)3− in M-type Gd(Ta1-xPx)O4: y at.% Tb3+ is x = 0.1 and y = 10 to obtain maximum luminous intensity, respectively. Moreover, the luminescence decay time of Tb3+ ions in Gd(Ta0.9P0.1)O4 matrix under optimized doping condition is about 1 ms and CIE chromaticity results imply the phosphors exhibit yellowish-green emission. These results suggest the Gd(Ta1−xPx)O4: y at.% Tb3+ phosphors are promising candidates for LED luminescence or medical imaging applications.

Radiation properties of burning clouds of metal dust. 2. Experimental research

The dynamics of the time variation of the flame front radius, combustion temperature, and radiation characteristics (integrated radiation flux in the range of 2–20 μm, luminous intensity, specific light sum) of burning clouds of metal dust (aluminum, aluminum-magnesium alloy, aluminum hydride) with a volume of more than 10 m3 was experimentally studied. It is shown that the radiative characteristics of large clouds correspond to those for small volumes (V = 5 L). It has been established that aerosuspensions of aluminum and aluminum hydride have the maximum luminous intensity, and the time of their luminescence in the infrared region exceeds the luminescence times of other compositions. Despite the high lighting performance of aluminum hydride aerosuspensions, the specific light sum of such air suspensions is low, due to their high burning rate. A comparison of the lighting performance of burning clouds of aerosuspension of metal particles with those for photo mixtures in lighting pyrotechnic compositions shows that the luminous intensities and specific light sums of air suspension are higher than those of pyrotechnic compositions and approximately the same for photo mixtures. However, the duration of combustion of an aerosuspension is usually two orders of magnitude longer than the duration of the flash of the mixture, much more than the volume of the radiation source. For clouds of aluminum and magnesium, the existence of noise-like radio-frequency radiation in the range 1–40 GHz was first discovered. It was shown that the radio-frequency spectrum is not of a thermal nature, non-linearly dependent on frequency, and its total energy intensity in the indicated range was of the order of hundredths of a W/m3. The influence of bremsstrahlung on the radio emission characteristics of burning clouds was analyzed.