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To develop non-rare-earth or metal-free phosphors for white light-emitting diodes (WLEDs) are very significant and forward-looking. Here, a yellow-green-emitting g-C 3 N 4 derivative (p -Ph-g-C 3 N 4) consisting of 1,4-phenylene-inserted heptazine units was successfully prepared by 6,6'-(1,4-phenylene)bis(1,3,5-triazine-2,4-diamine) via thermal polymerization. Its emission is mainly located at 450–700 nm with the maximum wavelength (λ em,max) of 536 nm, its quantum yield (QY) is 15.7% (λ ex = 430 nm) which is much higher than that of bulk g-C 3 N 4 (ca. 5%). Under the excitation of 430 nm blue-emitting GaN-based chips (ca. 4.0 lm·W−1), p -Ph-g-C 3 N 4 together with non-rare-earth red-emitting K 2 SiF 6 :Mn4+ as phosphors, a series of cold, neutral, and warm WLEDs with good performances were fabricated. As for the best one, its color rendering index (CRI) is 84.3, correlate color temperature (CCT) is 5702 K, luminous efficiency (LE) is 5.40 lm·W−1, moreover, its CIE value (0.30, 0.34) is very close to (0.33, 0.33) of pure white light. The research results indicate p -Ph-g-C 3 N 4 can be used as an efficient metal-free quasi-green phosphor for WLEDs. White LEDs were fabricated by a yellow-green-emitting g-C 3 N 4 derivative and red-emitting K 2 SiF 6 :Mn4+ under the excitation of blue-emitting chips. [Display omitted] • A yellow-green-emitting metal-free g-C 3 N 4 derivative. • The derivative consisting of 1,4-phenylene-inserted heptazine units. • Cold/neutral/warm WLEDs all being fabricated. [ABSTRACT FROM AUTHOR]

Abstract Red-emitting phosphor Rb 5 Nb 3 OF 18 :Mn4+ was prepared by an ion exchange method and its crystal structure, luminescent properties and application were discussed. Mn4+ in Rb 5 Nb 3 OF 18 which has appropriate band gap experiences a strong crystal field and emits intense red light around 633 nm with one broad excitation band at ∼470 nm. In addition, the light-emitting diodes (LEDs) coated Rb 5 Nb 3 OF 18 :Mn4+ exhibit excellent luminescent performances, such as the white LED can emit warm white light with high luminous efficiency (113.6 lm/W). Hence, Rb 5 Nb 3 OF 18 :Mn4+ could be a potential red component for white LEDs. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

A novel red-emitting cationic iridium(III) coordination polymer using 2-(9-(2-ethylhexyl)-9 H -carbazol-3-yl)benzo[ d ]thiazole as main ligands, 4,4′-bipyridine as bridging auxiliary ligands and Cl ˉ as anions was synthesized. It had high thermal stability with a thermal decomposition temperature ( T d ) of 345 °C and low thermal quenching with an activation energy ( E a ) of 0.2760 eV, with the temperature increasing from 20 °C to 100 °C, its photoluminescent intensity decreased to 76.7%. It can be efficiently excited by blue light of GaN chips, the cold white light of GaN-based LEDs using only Y 3 Al 5 O 12 :Ce 3+ (YAG:Ce, 7.0 wt% in silicone) as phosphors can become warmer when it was blended in. When blending concentrations were 0.1 wt% and 0.2 wt%, the cold white light became neutral white light, the correlated color temperature (CCT) decreased from 6157 K to 5240 K, then to 4043 K, the color rendering index (CRI) changed from 72.7 to 81.3, then to 78.6, the luminous efficiency ( η L ) changed from 134.1 lm·w −1 to 61.9 lm·w −1 , then to 46.3 lm·w −1 , the Commission Internationale de L'Eclairage (CIE) chromaticity coordinates changed from (0.32, 0.33) to (0.34, 0.33), then to (0.38, 0.36). At 0.3 wt%, the light became warm white light, the corresponding CCT was 3475 K, CRI was 75.6, η L was 36.9 lm·w −1 , and CIE value was (0.41, 0.40). The results suggest the coordination polymer is a promising red-emitting phosphor candidate for neutral and warm white LEDs, especially for warm white LEDs. [ABSTRACT FROM AUTHOR]

Searching for efficient Mn4+ red phosphors for white lighting and display backlighting has drawn great attention. In this work, an efficient Mn4+-doped fluoroscandate, Rb 2 KScF 6 :Mn4+, with short fluorescence lifetime is prepared via a facile co-precipitation method. It was found that the nonequivalent occupation of Mn4+ for Sc3+ leads to the identifications of sharp red emissions, enhanced zero-phonon line, high quantum efficiency and short fluorescence lifetime upon blue light excitation. Thanks to the luminescent properties, good optical parameters of high color rendering index, low correlated color temperature, and acceptable color gamut were achieved by coating the red Rb 2 KScF 6 :Mn4+ phosphor with yellow Y 3 Al 5 O 12 :Ce3+ or green β -SiAlON:Eu2+ phosphor in various white light-emitting diodes, demonstrating its potential role for white light illumination and backlight display applications. • The crystal and electronic structures were analyzed for a novel Rb 2 KScF 6 :Mn4+ phosphor. • The luminescent properties including an enhanced zero-phonon line and a short fluorescence lifetime were confirmed. • The optical behavior of the Rb 2 KScF 6 :Mn4+ phosphor in multiple white light-emitting diodes was elucidated. [ABSTRACT FROM AUTHOR]

A sp2-carbon-linked covalent organic framework (COF) containing tetraphenylethene units was successfully synthesized by using 2,2'-(1,4-phenylene)diacetonitrile and 4′,4‴,4‴'',4‴''''-(Ethene-1,1,2,2-tetrayl)tetrakis(([1,1′-biphenyl]-4-carbaldehyde)) as monomers. After being investigated by powder X-Ray diffraction (PXRD), nitrogen adsorption-desorption and theoretical calculations, the dual-pore eclipsed Kagome structure (AA-K) of the COF was confirmed. The COF emitted bright yellow light with a solid-state photoluminesce quantum yield (PLQY) of 39.2%. It exhibited high thermal stability with a thermal decomposition temperature (T d) of ca. 610 °C, and its relative emission intensity at 90 °C was nearly 80.0% of that at 30 °C. The COF was blended in epoxy resin at different concentrations and used as phosphors, excited by GaN-based blue-emitting chips (λ em,max ≈ 455 nm), a series of white light-emitting diodes (WLEDs) with different correlated color temperature (CCT) can be obtained. At 1.5 wt%, a cold WLED was obtained, its CCT was 6125 K, color rendering index (CRI) was 83.4, Commission Internationale de L'Eclairage (CIE) chromaticity coordinate was (0.32, 0.29), luminous efficiency (η L) was 20.31 lm·W−1. At 2.0 wt%, a neutral WLED was obtained, its CCT was 4293 K, CRI was 79.6, chromaticity coordinate was (0.36, 0.34) and η L was 19.71 lm·W−1. At 2.5 wt%, a warm WLED was obtained, its CCT was 3348 K, CRI was 69.4, chromaticity coordinate was (0.42, 0.42) and η L was 18.81 lm·W−1. The results suggested the COF can be used promising metal-free phosphors in WLEDs. [Display omitted] • A sp2-carbon-linked covalent organic framework (COF) containing tetraphenylethene units was synthesized. • The COF emitted bright yellow light with a solid-state photoluminesce quantum yield (PLQY) of 39.2%. • The thermal decomposition temperature (T d) of the COF was as high as 610 °C. • Cold/neutral/warm white LEDs with high performances were prepared by using the COF and blue-emitting chips. [ABSTRACT FROM AUTHOR]

A novel reddish-orange-emitting cationic iridium(III) complex [(PPP) 2 Ir(BPPO)]PF 6 (PPP: 2-(4-pentylphenyl)pyridine; BPPO: 2-(4-(tert -butyl)phenyl)-5-(pyridin-2-yl)-1,3,4-oxadiazole) was synthesized and doped in silica gel via a simple sol-gel method. By comparing photoluminescence (PL) intensity of the composites containing [(PPP) 2 Ir(BPPO)]PF 6 at different doping concentrations, the composite containing 12.5 wt% [(PPP) 2 Ir(BPPO)]PF 6 was determined as the best target product due to its highest PL intensity. This composite showed higher thermal stability and lower thermal quenching property than those of pure [(PPP) 2 Ir(BPPO)]PF 6 , their thermal decomposition temperatures (T d) were 350 °C and 320 °C, their PL intensities at 150 °C were 70.8% and 35.8% of those at 30 °C, respectively. Excited by blue-emitting GaN-based chips, both of pure [(PPP) 2 Ir(BPPO)]PF 6 and the composite can be used as phosphors for fabricating reddish-orange LEDs. Moreover, the cold white light of the LEDs fabricated by blue-emitting GaN-based chips and yellow-emitting Y 3 Al 5 O 12 :Ce3+ (YAG:Ce) can be adjusted into neutral/warm white with good performances when pure [(PPP) 2 Ir(BPPO)]PF 6 or the composite was added in the LEDs as red light sources. Relatively, the LEDs using the composite were much more efficient than the LEDs directly using pure [(PPP) 2 Ir(BPPO)]PF 6 at the same amounts. Cationic iridium(III) complexes being doped into silica gel is an effective way for their application as phosphors in LEDs. [Display omitted] • A novel reddish-orange-emitting cationic iridium(III) complex was synthesized and doped in silica gel. • The complex in silica gel showed higher luminous efficiency, higher thermal stability and lower thermal quenching than the pure complex. • Efficient neutral and warm white light-emitting diodes were fabricated by using the composite and Y 3 Al 5 O 12 :Ce3+ as phosphors. [ABSTRACT FROM AUTHOR]

• Cs 2 KCrF 6 :Mn4+ was designed and prepared at mild conditions. • Cs 2 KCrF 6 :Mn4+ exhibits high blue-light conversion efficiency. • Cs 2 KCrF 6 :Mn4+ has excellently thermal quenching property and color stability. • Cs 2 KCrF 6 :Mn4+ can improve the luminescent performances of w-LED. One red phosphor Cs 2 KCrF 6 :Mn4+ (CKCFM) with the cubic structure was prepared at mild conditions. Mn4+ in CKCFM with the highly symmetrical environment exhibit one broad excitation band peaking at 453 nm and narrow-band emission in the range from 600 to 650 nm. The optimized CKCFM has one highly external quantum yield of 46.7%. At the same time, the sample also has excellent thermal stability and color stability. The emission intensity of CKCFM at 160 °C is still higher than that at 20 °C. At last, one white light-emitting diode (w-LED) was obtained by combining CKCFM and Y 3 Al 5 O 12 :Ce3+with one blue LED chip. It shows excellent performance: color rendering index (Ra) up to 88.3, color temperature (CCT) down to 3986 K, showing that CKCFM can find application in w-LEDs. New red-emitting phosphor Cs 2 KCrF 6 :Mn4+ exhibits high blue-light conversion efficiency and a high thermal-quenching temperature for w-LEDs. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, we present a novel Mn4+-activated Rb 2 NaAlF 6 red phosphor synthesized through a cation exchange route at room temperature. The structural and optical features were characterized by X-ray diffraction, energy dispersive X-ray spectrometer, scanning electron microscopy, X-ray fluorescence, emission, excitation, and luminescence decay curves. The straightforward evidences have shown that the as-prepared Rb 2 NaAlF 6 :Mn4+ crystallizes into single cubic phase with regular octahedral particulate morphology, and exhibits broad excitation band and sharp emission lines in the red and blue regions. The luminescence properties, thermal stability and optical performance were systematically investigated to recognize the luminescence behavior of Rb 2 NaAlF 6 :Mn4+ and its potential application for white light illumination. The results suggest that the Rb 2 NaAlF 6 :Mn4+ phosphor exhibits excellent thermal stability and is capable of tuning the cold white light to warm in white light-emitting diodes. A novel fluoroaluminate red-emitting phosphor of Rb 2 NaAlF 6 :Mn4+, showing regular octahedral particulate morphology, outstanding thermal stability, intense red emission lines and broad blue excitation band characteristics, was presented in this work. With the introduction of this phosphor, the R a and T c data of commercial WLED can be significantly improved, indicating its potential use for warm white light illumination. Image 1 • The red luminescence from a novel Rb 2 NaAlF 6 :Mn4+ red phosphor was presented. • The crystal structure and luminescence properties have been confirmed. • The concentration quenching mechanism and optical performance have been elucidated. [ABSTRACT FROM AUTHOR]

Herein, a red-emitting phosphor Ba 2 HfF 8 :Mn4+ was successfully synthesized by the hydrothermal method. This phosphor is of the similar orthorhombic structure with that of Ba 2 ZrF 8 :Mn4+ confirmed by the Rietveld refinement. The as-prepared Ba 2 HfF 8 :Mn4+ exhibits excellent red emission with a strengthened zero phonon line of Mn4+ under the blue-light excitation, indicating that Mn4+ experiences the low symmetry environment in this phosphor. Meanwhile, Mn4+ in the sample Ba 2 HfF 8 :Mn4+ (8.7 mol%) has the shorter decay time, compared with that in some hexafluoride phosphors. The white light-emitting diode (wLED) based on Ba 2 HfF 8 :Mn4+ (8.7 mol%) and Y 3 Al 5 O 12 :Ce3+ presents the excellent photoelectric performances with wide color gamut. So, Ba 2 HfF 8 :Mn4+ as a new red phosphor could find potential application on the backlight for displays. One new red-emitting phosphor Ba 2 HfF 8 :Mn4+ presents intense red emission with a strengthened zero phonon line and short decay time of luminescence fo r white LEDs. Image 1 • A new phosphor Ba 2 HfF 8 :Mn4+ was successfully synthesized by the hydrothermal method. • This phosphor exhibits excellent red emission with a strengthened zero phonon line. • This phosphor has the short decay time for LCD application. • A w-LED coating this sample has excellent performances with wide color gamut. [ABSTRACT FROM AUTHOR]