Improved quantum efficiency of Sr(Al,Si)5(O,N)7:Ce3+ by selection of Ce raw material

The luminescence properties of yellow-emitting Ce³⁺-doped Sr-containing sialon phosphor Sr(Al,Si)₅(O,N)₇:Ce³⁺ were notably improved by the Ce raw material selection. By changing the Ce raw material from oxides to nitrides or chlorides, the emission wavelength shifted to above 560 nm, which is beneficial for higher color rendering index white light-emitting diodes. This result from an increase in the covalency of the host crystal being associated with a decrease in the oxygen content. When Ce chloride was used, both the absorption and internal quantum efficiency increased, resulting in an increase in the external quantum efficiency up to 65%–72%. Inductively coupled plasma mass spectrometry, X-ray diffraction, and electron spin resonance measurements showed that the reason for the absorption increase is an increase in Ce³⁺ content and suppression of the generation of the second phase, and the reason for the increase in the internal quantum efficiency is a decrease in the host crystal absorption via suppression of anion vacancy generation. It was found that Ce chloride not only suppresses oxygen impurities but also acts as a flux that results in improved crystallinity.     

Strong f-f excitation in titanium silicate: Near-UV LED pumped red phosphors with outstanding temperature sensitivity

Optical thermometry and white light-emitting diodes (WLEDs) are the research hotspots for Eu³⁺ doped phosphors. In this study, a series of Sr₂TiSi₂O₈: Eu³⁺ red phosphors were developed in a solid-state reaction method. The luminescent properties of the Sr₂TiSi₂O₈: Eu³⁺ phosphor illustrate that Sr₂TiSi₂O₈: Eu³⁺ is effectively excited by the NUV LED chip and emit an intense red light with a peak of 618 nm due to the noninversion symmetry coordination of Eu³⁺ in Sr₂TiSi₂O₈. The local coordination environment of Eu³⁺ was investigated in detail using crystallographic data, spectroscopic data and Judd–Ofelt parameters. In addition, the emission intensity of Sr₂TiSi₂O₈:Eu³⁺ is extremely sensitive to temperature. The relative sensitivity of Sr₂TiSi₂O₈:Eu³⁺ is 1.1% k^-1@300 k, which is comparable to other Eu³⁺-activated temperature sensing materials. The possible mechanism of the temperature sensitive quenching characteristics was proposed. The results indicate that Sr₂TiSi₂O₈:Eu³⁺ is a potential temperature sensing material.     

Development of silicon wafer packaging technology for deep UV LED

This paper reports a deep‐ultraviolet LED (deep‐UV‐LED) package based on silicon MEMS process technology (Si‐PKG). The package consists of a cavity formed by silicon crystalline anisotropic etching, through‐silicon vias (TSVs) filled with electroplated Cu, bonding metals made of electroplated Ni/AuSn and a quartz lid for hermetic sealing. A deep‐UV LED die is directly mounted in the Si‐PKG by AuSn eutectic bonding without a submount. It has advantages in terms of size, heat dissipation, light utilization efficiency, productivity and cost over conventional AlN ceramic packages. We confirmed a light output of 30 mW and effective reflection on Si (111) cavity slopes in the Si‐PKG. Based on simulation, further improvement of the optical output is expected by optimizing DUV‐LED die mount condition.     

Gas‐phase removal of indoor volatile organic compounds and airborne microorganisms over mono‐ and bimetal‐modified (Pt,Cu, Ag) titanium(IV) oxide nanocomposites

The photocatalytic deactivation of volatile organic compounds and mold fungi using TiO₂ modified with mono‐ and bimetallic (Pt, Cu, Ag) particles is reported in this study. The mono‐ and bimetal‐modified (Pt, Cu, Ag) titanium(IV) oxide photocatalysts were prepared by chemical reduction method and characterized using XRD, XPS, DR/UV‐Vis, BET, and TEM analysis. The effect of incident light, type and content of mono‐ and bimetallic nanoparticles deposited on titanium(IV) oxide was studied. Photocatalytic activity of as‐prepared nanocomposites was examined in the gas phase using LEDs array. High photocatalytic activity of Ag/Pt‐TiO₂ and Cu/Pt‐TiO₂ in the reaction of toluene degradation resulted from improved efficiency of interfacial charge transfer process, which was consistent with the fluorescence quenching effect revealed by photoluminescence (PL) emission spectra. The photocatalytic deactivation of Penicillium chrysogenum, a pathogenic fungi present in the indoor environment, especially in a damp or water‐damaged building using mono‐ and bimetal‐modified (Pt, Cu, Ag) titanium(IV) oxide was evaluated for the first time. TiO₂ modified with mono‐ and bimetallic NPs of Ag/Pt, Cu, and Ag deposited on TiO₂ exhibited improved fungicidal activity under LEDs illumination than pure TiO₂.     

Warm-white light performance of Dy3+, Eu3+: NaLa(WO4)2 phosphors excited with a 450-nm LED

Dy³⁺, Eu³⁺: NaLa(WO₄)₂ phosphors are successfully synthesized through the solid-state reaction technique. The phase-structure and morphology are measured via X-ray diffraction and energy dispersive spectrometry. The concentrations of Dy³⁺, Eu³⁺, La³⁺, and W⁶⁺ are measured via ICP. The absorption and excited spectra are presented, which indicate that a blue band ranging from 430 to 480 nm is suitable for excitation. Using a commercial blue LED with a wavelength of 450 nm as the excitation light source, emission spectra for samples with varying dopant concentration ratios of Dy³⁺ to Eu³⁺ are obtained, which show good tunable yellow and red emission. For the purpose of investigating white LED performance, CIE spectra and a white light photo are also presented. The results reveal that varying the dopant concentration ratio of Dy³⁺ to Eu³⁺ plays a key role in the warm-white performance. With increasing concentration of Eu³⁺, the correlated color temperature decreases from 4069 to 3172 K, which indicates good warm-white performance.     

Impacts of spectral variations in multiwavelength excitation method on measurements of fluorescently whitened papers

The multiwavelength excitation (MWE) method for measuring the colorimetric properties of fluorescent whitening agent (FWA)‐treated specimens illuminated by a standard daylight illuminant computationally approximates not the spectral power distribution (SPD) of the illuminant but the luminescent SPD excited thereby by a weighted sum of the luminescent SPDs excited by a few different narrow‐band illuminations. The weights are optimized for the actual SPDs of those illuminations and the bispectral luminescent radiance factors of typical FWA‐treated paper specimens. Since the latter is invariant among instruments once provided as the common numerical data, the variations of the narrow‐band SPDs give major impacts to the reproducibility of this method. The weights optimized for the varied SPDs, however, mitigate the impacts. For investigating how they impact, one basic illumination system and its 16 simple variation systems were built virtually. The basic system consists of three narrow‐band LEDs and one blue‐excited white LED, whereas the individual simple variation system has either the peak wavelength or spectral width of one of the four LEDs (including the blue LED in the white LED) varied. With those systems, seven FWA‐treated papers with the known bispectral radiance factors were measured computationally by simulating the procedure of the MWE method. The differences in the colorimetric values measured with the simple variation systems from those with the basic system are far below the just noticeable difference, which indicates that the MWE method can be a practical solution for better reproducibility in measuring FWA‐treated papers.     

城市隧道照明设计探讨

根据近些年的城市隧道工程设计经验,介绍了隧道照明的设计依据、标准及基本要求,分析了城市隧道照明设计的照明标准值、灯具布置、应急照明、照明控制、配线、节能措施等方面内容,并对隧道照明工程设计实例进行了探讨。     

Enhancement of the luminous efficiency of a ceramic phosphor plate by post-annealing for high-power LED applications

Currently, phosphor-converted white light-emitting diodes offer low energy consumption, good environmental stability, and a long lifetime. Hence, they are widely utilized in high-power light-emitting diode (LED) applications such as those in the automotive headlamp industries. However, obtaining high luminous efficiency of such diodes is challenging because of their internal structural properties such as micropores. Herein, we developed phosphor-in-glass (PiG) plates by mixing a blue LED chip and yellow phosphor to create high-power white LEDs (w-LEDs). In addition, the influence of post-annealing on the prepared PiG plates at different temperatures (350°C-550 °C) was investigated. Post-annealing, a treatment that facilitates the mobility of the ceramic matrix encapsulating the phosphor powder, decreases an LED's porosity, thereby enhancing its overall luminous efficiency. Results show that PiG plates post-annealed at 450 °C exhibit superior optical performance and effective color properties than PiG plates that were non-annealed or post-annealed at 350 °C, 400 °C, 500 °C, and 550 °C. Therefore, post-annealed PiG plates are more suitable potential materials for application in the high-power LED industry.     

Improving performance of high-power indium gallium nitride/gallium nitride-based vertical light-emitting diodes by employing simple n-type electrode pattern

In this work, simple n-type electrode structures were used to enhance the electrical and optical performances of fully packaged commercially mass-produced vertical-geometry light-emitting diodes (VLEDs). The forward bias voltage of the VLED with a Y-pattern electrode increased less rapidly than that of VLEDs with a reference electrode. The VLEDs with the reference and Y-pattern electrodes exhibited forward voltages of 2.93±0.015 and 2.89±0.015 V at 350 mA and 3.77±0.015 and 3.53±0.015 V at 2000 mA, respectively. The VLEDs with the Y-pattern electrode resulted in a higher light output than the VLEDs with the reference electrode with increase in the drive current to 2000 mA. The emission images showed that the VLEDs with the Y-pattern electrode exhibited better current spreading behavior and lower junction temperatures than the VLEDs with the reference electrode. With increase in the current from 350 to 2000 mA, the VLEDs with the Y-pattern electrode experienced a 39.4% reduction in the wall plug efficiency, whereas the VLEDs with the reference electrode suffered from a 43.3% reduction.     

光控太阳能装饰灯的设计与实现

太阳能光伏能够提供较为稳定的直流电源,是目前最受欢迎的绿色能源之一;而LED(发光二极管)则是直流电控制光源,两者的结合已有诸多研究。本文设计了一款单片机控制和光自动控制相结合的太阳能装饰灯,集美观、实用、节能等理念于一体。