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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]

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]

Red-emitting phosphor plays a critical role in improving performance of the phosphor-converted white light-emitting diodes (pc-WLEDs). Herein, a red-emitting phosphor, Rb 2 TiF 6 :Mn 4+ , was synthesized via the ion exchange method under mild condition. The crystal structure and morphology were characterized by the powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The Rietveld refinements of Rb 2 TiF 6 :Mn 4+ indicate that this sample is of single phase with hexagonal crystal structure. The as-prepared Rb 2 TiF 6 :Mn 4+ has sharp red emissions with broad excitation band at ∼460 nm. The luminescent behavior of Mn 4+ was discussed in detail. The temperature-dependent emission spectra of Rb 2 TiF 6 :Mn 4+ indicate that this phosphor shares high thermal quenching resistance and excellent color stability. A series of WLEDs with tunable color rendering index and color temperature were fabricated by combining commercial Y 3 Al 5 O 12 :Ce 3+ and Rb 2 TiF 6 :Mn 4+ on blue GaN-LED chips. With the addition of Rb 2 TiF 6 :Mn 4+ , WLED with wide gamut was obtained with low color temperature (3123 K), high color rendering index (91.5) and high luminous efficacy (187.9 lm/W). These findings show this phosphor could be a promising commercial red phosphor in wide color-gamut WLEDs. [ABSTRACT FROM AUTHOR]

Red phosphors K 2 XF 6 :Mn 4+ (X = Ti, Si and Ge) have been successfully synthesized by one-pot chemical co-precipitation method in low HF concentration with the addition of acetic acid glacial. The crystal structure and morphology of these phosphors were characterized by powder X-ray diffraction (XRD), scanning-electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS) in detail. Their optical properties were investigated by excitation and emission spectra, diffuse reflectance spectra, and decay curves. These phosphors exhibit intense red emission with high color-purity under blue light excitation. Finally, the applications on the white-light-emitting diodes (WLEDs) of the as-prepared sample were investigated. The WLEDs fabricated with K 2 XF 6 :Mn 4+ display warm white light with lower color temperature ( T c < 4000 K) and higher color rendering index ( Ra > 80). [ABSTRACT FROM AUTHOR]

Red-emitting phosphors LaBSiO 5 :Eu 3+ and LaBSiO 5 :Eu 3+ , Al 3+ were synthesized by the conventional solid state method at 1100 °C. The structure and luminescent properties of these phosphors are investigated. LaBSiO 5 :Eu 3+ and LaBSiO 5 :Eu 3+ , Al 3+ could be efficiently excited by near ultraviolet light with the strongest excitation peak at 395 nm. The main emission peak is located at around 616 nm, which corresponds to the transition of 5 D 0 → 7 F 2 of Eu 3+ ions. The emission intensity of LaBSiO 5 :Eu 3+ was enhanced by introducing Al 3+ ions. Compared with Y 2 O 2 S:0.05Eu 3+ , the sample La 0.70 B 0.75 SiO 5 :0.30Eu 3+ , 0.25Al 3+ shares the intense red emission, and its emission intensity is about 3.8 times as strong as that of Y 2 O 2 S:0.05Eu 3+ under 395 nm light excitation. Bright red light can be observed from the red LED based on La 0.70 B 0.75 SiO 5 :0.30Eu 3+ , 0.25Al 3+ , hence La 0.70 B 0.75 SiO 5 :0.30Eu 3+ , 0.25Al 3+ maybe find application on near-UV InGaN-based white LEDs. [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]

A reddish-orange-emitting cationic iridium(III) complex [(dfppy) 2 Ir(EPTC)]PF 6 (dfppy: 2-(2,4-difluorophenyl)pyridine, EPTC: 9-ethyl-3-(3-(pyridin-2-yl)-1,2,4-triazin-5-yl)-9 H -carbazole) containing a carbazole-triazine bipolar unit was synthesized. The thermal decomposition temperature (T d) of the complex was 355 °C, its relative emission intensity at 100 °C was 78.6% of that at 20 °C, which was enough for it to be used in LEDs. Mainly due to the bipolar unit, [(dfppy) 2 Ir(EPTC)]PF 6 can efficiently absorb and be excited by blue light (λ em,max = 457 nm) of GaN chips. Excited by blue-emitting GaN chips, the complex can be used for fabricating reddish-orange LEDs, moreover, together with yellow-emitting Y 3 Al 5 O 12 :Ce3+ (YAG:Ce), neutral and warm white light-emitting diodes (WLEDs) can be obtained with good performances. When [(dfppy) 2 Ir(EPTC)]PF 6 was blended in silicone at 1.0, 1.5 and 2.0 wt% respectively, all together with YAG:Ce at 4.0 wt%, three efficient neutral WLEDs were obtained. Their correlate color temperatures (CCT) were 4874 K, 4312 K and 3665 K, color rendering indexes (CRI) were 80.2, 78.3 and 76.4, luminous efficiencies (η L) were 88.5 lm·W−1, 83.6 lm·W−1 and 67.4 lm·W−1, Commission International de I'Eclairage (CIE) values were (0.34, 0.32), (0.36, 0.33) and (0.38, 0.33) respectively. When blending concentration of [(dfppy) 2 Ir(EPTC)]PF 6 was increased to 2.5 wt% together with YAG:Ce still at 4.0 wt%, a warm WLED was obtained, its CCT was 3282, CRI was 73.9, η L was 63.0 lm·W−1, and CIE value was (0.40, 0.35). Image 1 • A reddish-orange-emitting cationic iridium(III) complex containing a carbazole-triazine bipolar unit.. • The complex can be efficiently excited by blue-emitting GaN chips mainly due to the effect of the bipolar unit. • Together with Y 3 Al 5 O 12 :Ce3+ as phosphors, neutral and warm white light-emitting diodes can be obtained with good performances. [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]