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Due to the "efficiency droop" effect of light-emitting diodes (LEDs) under high drive currents, laser diode (LD) driven light sources are considered to replace LED lighting for the next-generation solid-state-lighting technology. In this Perspective, the history of lighting technology and the intrinsic advantages of LDs lighting are outlined. We provide a comparative overview of several typical LD phosphors, such as single crystal, transparent ceramic, phosphor-in-glass, and film thereof, as well as surface texture modification of film-type phosphor plates. The relationship between the illumination characterizations (luminance saturation, conversion efficiency, extraction efficiency, illuminating directionality, and color spatial uniformity) with thermal conductivity, pores, defects, second phases, and surface roughing or patterning is discussed. Finally, the current challenges and prospects are highlighted to provide guidelines for future research on LD phosphors. [ABSTRACT FROM AUTHOR]

Nowadays, major commercial w-LEDs fabricated by the traditionally gold-wire-welding packaging technology have undergone considerable development as indoor/outdoor lighting sources due to its high-energy utilization efficiency, long service life, environmental friendliness, and excellent chromatic stability. While, new generation applications in projections, automotive lighting, street lighting, plaza lighting, and high-end general lighting need further improvements in power handling and light extraction. Herein, transparent Ce:YAG glass-ceramics (GCs) phosphor was prepared by low-temperature co-sintering polycrystalline Ce:YAG phosphor powder and home-made PbO-B 2 O 3 -ZnO-SiO 2 glass powder. Thereafter, the flip-chip (FC) w-LEDs were fabricated with the GCs phosphor plates and FC blue chips. The GCs-based FC w-LEDs show not only excellent heat- and humidity-resistance characteristics, but also superior optical performances with an LE of 112.8 lm/W, a CRI of 71.2, a CCT of 6103 K as well as a chromaticity coordinate of (0.3202, 0.3298), under a high operation current of 400 mA. The technology route will open a practically commercial feasible approach to achieve excellent performances for advanced high-power FC w-LEDs. [ABSTRACT FROM AUTHOR]

YAG:Ce phosphors are synthesized by the vacuum sintering method, and their crystal structure, luminescence properties, and X-ray photoelectron spectroscopy are discussed. The synthesized temperature of pure YAG phase is reduced by vacuum sintering. As-synthesized YAG:Ce phosphors show a smaller average size of about 1mm due to the fine starting materials, low sintering temperature, and the absence of flux. It is found that samples synthesized by the vacuum sintering method show stronger emission intensity and higher optimized Ce3+-doping concentration. In addition, white light-emitting diodes (LEDs) with improved color-rendering properties are obtained by using modified Pr3+-doped YAG:Ce phosphors. [ABSTRACT FROM AUTHOR]

Composite phosphor ceramics were fabricated for white light-emitting diodes (LEDs) employing the tape-casting. Benefiting from the superposition of different emission spectrum, wider emission spectra of composite ceramics were reached, result in a higher color rendering index (CRI) of ceramic-based WLED. The composite structure and fluorescent property of composite ceramics were analyzed and the optical properties of ceramic-based WLED were tested. A ceramic-based WLED with a maximum CRI value of ∼83 was reached when (Ce,Gd):YAG and (Ce,Pr):YAG were employed for the composite ceramics. [ABSTRACT FROM AUTHOR]

Abstract: Ce3+/Eu2+ co-doped Li2SrSiO4 phosphor yields two emission bands consisted of blue and yellow components, which shows great potential as single host white phosphor for white LEDs. Effective energy transfer occurs in Ce3+/Eu2+ co-doped Li2SrSiO4 due to large spectral overlap between the emission of Ce3+ and excitation of Eu2+. Co-doping of Ce3+ enhances the emission intensity of Eu2+ greatly by transferring its excitation energy to Eu2+. The Ce3+ →Eu2+ energy transfer, thoroughly investigated by their absorption, excitation and photoluminescence decay behaviors, is demonstrated to be in the mechanism of electric dipole–dipole interaction. [Copyright &y& Elsevier]

Transparent Ce 3+ :Lu 3 Al 5 O 12 ceramics were successfully fabricated by combining tape-casting method and direct-forming method with solid-state sintering. The in-line optical transmittance and absorption spectra of as-sintered and air-annealed Ce:LuAG ceramics were comparely studied. XPS spectra indicated Ce 3+ and Ce 4+ ions co-existed in the prepared ceramics. Energy levels splitting of Ce 3+ in LuAG hosts were investigated based on broad-band emission from 500 nm to 700 nm resulting from the electron transitions from 5d 1 excited levels ( 2 D) to 4f ground state of Ce 3+ ( 2 F 5/2 , 2 F 7/2 ). The fluorescence lifetimes at 540 nm were 50–60 ns and energy resolution of 12% was achieved at 22 Na (511 keV). When collaborated with InGaN-GaN LED chips, a maximum CRI of 55.8 with LE as high as 223.4 lm/W were demonstrated, indicating that Ce:LuAG ceramics had a promising potential for white light-emitting diodes. [ABSTRACT FROM AUTHOR]

• The Pr3+-doped BaZr 0.16 Mg 0.28 Ta 0.56 O 3 (BZMT) transparent ceramics were fabricated by the high-temperature solid-state reaction method with a tube furnace in oxygen. • The in-line transmission of 0.6 at%Pr3+:BZMT (thickness 1.0 mm) at 648 nm exhibits 72.0%, reaching nearly 93.4% of the theoretical value (77.1%). • The hypersensitive transition (3P 0 –3F 2) to LEDs did achieve a superb deep red luminescence under the excitement of 447 nm. Fluorescent transparent ceramics have aroused great interest because of their potential applications in high-power white light-emitting diode and laser diode lighting. Herein, Pr3+-doped BaZr0.16Mg0.28Ta0.56O3 (BZMT) transparent ceramics were prepared via the high-temperature solid-state reaction approach. The in-line transmission of 0.6 at%Pr3+:BZMT (thickness 1.0 mm) at 648 nm exhibits 72.0%, reaching nearly 93.4% of the theoretical value (77.1%). Moreover, research in detail on the emission features according to Pr3+ percentages in BZMT was conducted. The emission spectra displayed a deep red emission at 648 nm associated with the hypersensitive transition of 3P 0 →3F 2. As LEDs can achieve a superb deep red luminescence under the excitement of 447 nm, which also shows excellent thermal stability. This work opens a new route for the development of transparent ceramics with excellent deep red luminescence performance through hypersensitive transition for white LEDs. Pr3+-doped BaZr 0.16 Mg 0.28 Ta 0.56 O 3 transparent ceramics displayed a deep red emission at 648 nm under the excitement of 447 nm, associated with the hypersensitive transition of 3P 0 →3F 2. And this work opens a new route for the development of transparent ceramics with excellent deep red luminescence performance through hypersensitive transition for white LEDs [Display omitted]. [ABSTRACT FROM AUTHOR]

Abstract: The crystal structure and photoluminescence properties of Eu2+ doped Li2Ca0.7Sr0.3SiO4 phosphors were investigated. The Li2Ca0.7Sr0.3SiO4 is not an alloy between the tetragonal Li2CaSiO4 and hexagonal Li2SrSiO4 but crystallizes in orthorhombic structure similar to Li2(CaSr)SiO4. Photoluminescence properties of the Li2Ca0.7Sr0.3SiO4:Eu2+ phosphors, summarized in effective excitation in the UV region, strong emission in the blue light range (with a peak at 427nm) and the CIE chromaticity coordinate (0.154, 0.038), indicate this phosphor has great potential in UV-chip pumped white LEDs. White light output by mixing the Li2Ca0.7Sr0.3SiO4:Eu2+ blue and Li2SrSiO4:Eu2+ yellow phosphor was attempted. With proper molar ratio of these two compound phosphors, warm white light with CIE chromaticity coordinate close to that of the nature white light (0.33, 0.33) and color temperature about 5000K was obtained. The results indicated that the Li2Ca0.7Sr0.3SiO4:Eu2+ may become an important phosphor candidate for ultra-violet chip pumped and multi-phosphors converted white LEDs. [Copyright &y& Elsevier]

With the development of high-power white light-emitting diodes, transparent ceramics have attracted more and more attention. In this paper, highly transparent Eu-doped Ba(Zr 0.16 Mg 0.28 Ta 0.56)O 3 (Eu3+:BZMT) transparent ceramics with different Eu-doped concentrations were fabricated via a high-temperature solid-state reaction approach. For 1-mm-thickness sample, the in-line transmittance of Eu3+:BZMT transparent ceramics is 72.3% at 650 nm, which is almost 92.3% of the theoretical transmittance. The emission spectrum of Eu3+:BZMT is discovered at 575–650 nm (5D 0 →7F 1 (575–600 nm) and 5D 0 →7F 2 (600–650 nm)), which displays an orange-red emitting. Through the study of the variable temperature spectrum, an outstanding thermal stability has been observed in Eu3+:BZMT. The experiment suggests that Eu3+:BZMT can be potentially adopted as a red phosphor for high-power WLEDs. • The Eu3+:BZMT transparent ceramics were prepared by solid state reaction under oxygen atmosphere. • The Eu3+:BZMT transparent ceramics reach 99.9% of theoretical density and 92.3% of theoretical transmittance. • The Eu3+:BZMT transparent ceramics exhibit an excellent red light. • The Eu3+:BZMT transparent fluorescent ceramics have excellent thermal stability and color stability. [ABSTRACT FROM AUTHOR]