Red phosphor materials play a key role in improving the lighting and backlit display quality of phosphor-converted white light-emitting diodes (pc-WLEDs). However, the development of a red phosphor with simultaneous high efficiency, excellent thermal stability and high colour purity is still a challenge. In this work, unique non-concentration quenching in solid-solution Cs3Gd1 − xGe3O9:xEu3+ (CGGO:xEu3+) (x = 0.1–1.0) phosphors is successfully developed to achieve a highly efficient red-emitting Cs3EuGe3O9 (CEGO) phosphor. Under the optimal 464 nm blue light excitation, CEGO shows a strong red emission at 611 nm with a high colour purity of 95.07% and a high internal quantum efficiency of 94%. Impressively, this red-emitting CEGO phosphor exhibits a better thermal stability at higher temperatures (175–250 °C, >90%) than typical red K2SiF6:Mn4+ and Y2O3:Eu3+ phosphors, and has a remarkable volumetric negative thermal expansion (coefficient of thermal expansion, α = −5.06 × 10−5/°C, 25–250 °C). By employing this red CEGO phosphor, a fabricated pc-WLED emits warm white light with colour coordinates (0.364, 0.383), a high colour rendering index (CRI = 89.7), and a low colour coordinate temperature (CCT = 4508 K). These results indicate that this highly efficient red-emitting phosphor has great potential as a red component for pc-WLEDs, opening a new perspective for developing new phosphor materials. A luminescent material that undergoes an unusual heat-shrinking process shows promise for enhancing the efficiency of white light-emitting diodes (LEDs). Current technologies for generating white LEDs often combine near-ultraviolet light with background radiation from red, green, and blue phosphors. J.L. from China’s Changchun Institute of Applied Chemistry and colleagues have now developed a red phosphor that remains active at temperatures which shut down other red-light emitters. The team’s compound, a cesium-based metal oxide doped with rare earth ions, has a crystal structure that contracts upon heating and avoids symmetry-distorting effects associated with thermal quenching. This unique structure also supports higher dopant concentrations than typical phosphors for improved colour rendering in prototype white LEDs. A highly efficient red-emitting Cs3EuGe3O9 phosphor for high-performance pc-WLEDs is discovered with non-concentration quenching, favourable thermal stability, high colour purity and negative thermal expansion.

/pdf/thermally-stable-and-highly-efficient-red-emitting-eu3-doped-3epdl74b4d.pdf

Thermally stable and highly efficient red-emitting Eu3+-doped Cs3GdGe3O9 phosphors for WLEDs: non-concentration quenching and negative thermal expansion.

Poor water resistance and nongreen synthesis remain great challenges for commercial narrow red-emitting phosphor A2MF6:Mn4+ (A = alkali metal ion; M = Si, Ge, Ti) for solid-state lighting and display. We develop here a simple and green growth route to synthesize homogeneous red-emitting composite phosphor K2SiF6:Mn4+@K2SiF6 (KSFM@KSF) with excellent water resistance and high efficiency without the usage of toxic and volatile hydrogen fluoride solution. After immersing into water for 6 h, the as-obtained water-resistant products maintain 76% of the original emission intensity, whereas the emission intensity of non-water-resistant ones steeply drops down to 11%. A remarkable result is that after having kept at 85% humidity and at 85 °C for 504 h (21 days), the emission intensity of the as-obtained water-resistant products is at 80-90%, from its initial value, which is 2-3 times higher than 30-40% for the non-water-resistant products. The surface deactivation-enabled growth mechanism for these phosphors was proposed and investigated in detail. We found that nontoxic H3PO4/H2O2 aqueous solution promotes the releasing and decomposition of the surface [MnF6]2- ions and the transformation of the KSFM surface to KSF, which finally contributes to the homogeneous KSFM@KSF composite structure. This composite structure strategy was also successfully used to treat KSFM phosphor prepared by other methods. We believe that the results obtained in the present paper will open the pathway for the large-scale environmentally friendly synthesis of the excellent antimoisture narrow red-emitting A2MF6:Mn4+ phosphor to be used for white light-emitting diode applications.

Highly Stable K2SiF6:Mn4+@K2SiF6 Composite Phosphor with Narrow Red Emission for White LEDs

Finding efficient cyan phosphors with broadband absorption in the near-ultraviolet range (380–420 nm) and bright emission around 490 nm are highly important to make up for the so-called cyan gap (480–520 nm) in traditional tricolor (blue, green and red) phosphor-converted white light-emitting diodes (LEDs). Herein, we reported a new garnet phosphor, namely Ca2LuZr2(AlO4)3:Ce3+ (CLZA:Ce3+), with a cyan-emitting band, which enabled to fill the cyan gap and realize high color rendering white LEDs. The composition-optimized CLZA:1% Ce3+ phosphors showed an intense broad excitation band in the 370–475 nm wavelength range peaked at 408 nm and a broad asymmetric emission band at around 483 nm in the wavelength range of 414–650 nm. Importantly, the cyan-emitting CLZA:1% Ce3+ phosphors possessed a luminescence efficiency of 58%. Notably, the CLZA:1% Ce3+ cyan phosphors allowed to fill the cyan gap between the blue and green emission bands in white LEDs, and the value of color rendering index could be enhanced from 82.3 to 89.2. This study provides new insights into designing and developing suitable efficient phosphors for high-color-quality solid-state white lighting.

https://pubs.rsc.org/en/content/articlepdf/2020/tc/c9tc04952e

A broadband cyan-emitting Ca 2 LuZr 2 (AlO 4 ) 3 :Ce 3+ garnet phosphor for near-ultraviolet-pumped warm-white light-emitting diodes with an improved color rendering index

Ultra-high color rendering warm-white light-emitting diodes based on an efficient green-emitting garnet phosphor for solid-state lighting

A detailed nondestructive analytical method for quantitative food analysis was established by using a self-fabricated NIR-LED light source combined with Mg3Ga2GeO8 (MGGO) phosphor and a blue LED ch...

An Ultra-Broadband Near-Infrared Cr3+-Activated Gallogermanate Mg3Ga2GeO8 Phosphor as Light Sources for Food Analysis

Photoluminescence and cathodoluminescence properties of novel rare-earth free narrow-band bright green-emitting ZnB2O4:Mn2+ phosphor for LEDs and FEDs

Exploring new, efficient, and stable phosphors is important and meaningful work for both LEDs and FEDs. Here, the new Ce3+/Tb3+-codoped green-emitting phosphor Sr2LiScB4O10 with high energy transfe...

Sr2LiScB4O10:Ce3+/Tb3+: A Green-Emitting Phosphor with High Energy Transfer Efficiency and Stability for LEDs and FEDs

A novel yellow-green emitting phosphor with hafnium silicon multiple rings structure for light-emitting diodes and field emission displays

For exploring new and efficient luminescent materials, we developed an efficient narrow-band blue-emitting phosphor Eu2+ doped Na3CsMg7(PO4)6. Under near-ultraviolet light excitation, the phosphor can emit bright blue light with narrow...

An efficient blue phosphor with high thermal stability for lighting and optical pressure sensor applications

A series of nitride solid solutions (Ca1–xSrx)16Si17N34:0.03Eu2+ were successfully synthesized through the conventional solid-state method. The electronic crystal structure and photoluminescence characteristics were studied in detail. The excitation in the near-ultraviolet and blue regions of the samples shows a broad band in the 250–550 nm range, which can match well with the n-UV and blue lighting-emitting diode chips. Partial substitution of Ca2+ by Sr2+ results in a redshift emission, and the impacts of Sr content on the luminescence were researched in detail. Under 410 nm excitation, the phosphor exhibited tunable red emission from 616 to 653 nm by changing the concentration of Sr2+. Based on the crystal data, the emission can be fitted into three distinguished Gaussian components, which are attributed to the different Eu2+ luminescence centers occupied in three disparate Ca2+ (Sr2+) lattice sites. The temperature quenching property of the phosphor was also investigated, and the good thermal stabilit...

Synthesis, Crystal Structure, and Luminescence Properties of Tunable Red-Emitting Nitride Solid Solutions (Ca1-xSrx)16Si17N34:Eu2+ for White LEDs.

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