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A new red-emitting phosphor based on polyfluoride Na3Li3Sc2F12 doped with Mn4+ was prepared via a co-precipitation method at room temperature. Its crystal structure, luminescence properties and applications are discussed in detail. The as-synthesized phosphor emits red light with intense zero-phonon line (ZPL) at 618 nm under the excitation of 461 nm light. A higher energy of the 2Eg level of Mn4+ was observed in Na3Li3Sc2F12:Mn4+. The Racah parameters B and C were calculated to be 604 cm−1 and 3840 cm−1, respectively. The as-obtained Na3Li3Sc2F12:Mn4+ (4.86 mol%) shows a high internal quantum efficiency (IQE) of 66.8% and better resistance to thermal quenching. A white light-emitting diode (w-LED) with a high color rendering index of 92 and a low color temperature of 3694 K was fabricated. Hence, Na3Li3Sc2F12:Mn4+ as a new red-emitting phosphor has great potential application in w-LEDs. [ABSTRACT FROM AUTHOR]

Crystal phosphors have many unique advantages compared with powdery ones. Herein, room‐temperature‐grown millimeter‐sized single‐crystal phosphors of Cs2XF6:Mn4+ (X = Ge, Si, and Ti) with remarkably higher external quantum efficiency than the corresponding powdery samples are reported. In addition, as compared with the powdery ones, the crystal samples exhibit much better stability toward water under different pH conditions. The red light‐emitting diodes (LEDs) based on Cs2XF6:Mn4+ crystals show significantly improved luminous efficiency than those based on their corresponding powders. An assembled white LED device composed of the two layers of phosphors, i.e., the crystal (such as Cs2GeF6:Mn4+) and commercial Y3Al5O12:Ce3+, on a blue chip exhibits intense warm white light with high luminous efficiency (up to 193 lm W−1), high color rendering indexes (88), and low correlated color temperatures (3107 K). Hence, these crystals with greatly improved efficiency and stability can be potentially applied in high‐quality LED backlighting display and white LED lighting, especially inside the micro‐LED devices. [ABSTRACT FROM AUTHOR]

In current work, a red-emitting phosphor K2TiF6:Mn4+ was prepared by a facile method using H2O to replace high toxic HF as solvent at room temperature. Its structure and morphology were characterized by the XRD and SEM measurement. The obtained K2Ti0.96F6:0.04Mn4+ presents intense excitation band in the blue-light region and narrow-band emission with high color purity. Meanwhile, this sample is of the excellent thermal-quenching resistance and its emission intensity at 160 °C is still higher than that at 20 °C. The white light-emitting diode (wLED) fabricated with the commercial Y3Al5O12:Ce3+ and K2Ti0.96F6:0.04Mn4+ shows excellent photoelectric performances (the color rendering index of 88.4, the color temperature of 4138 K, and the luminous efficiency of 178.5 lm/W). So this as-synthesized phosphor may be find application on wLEDs. [ABSTRACT FROM AUTHOR]

In this work, a novel fluoroaluminate red phosphor of Cs2NaAl3F12:Mn4+ with excellent color purity was fabricated via the introduction of Mn4+ in the octahedral center. The crystal and electronic structures, luminescence properties and optical performances were characterized and investigated in detail. The evidences showed that Cs2NaAl3F12:Mn4+ well-crystallized into a single phase with particulate morphology, and the non-equivalent occupation in Cs2NaAl3F12 resulted in sharp red emissions with improved color purity upon blue light illumination. For solid-state lighting, the optical parameters consisted of the "blue-yellow-red" contributions significantly improved to a high color-rendering index of 88.7 and a low color temperature of 3856 K, indicating the potential use of Cs2NaAl3F12:Mn4+ for warm white light-emitting diode applications. [ABSTRACT FROM AUTHOR]

New red-emitting phosphors KLiSnF 6 : x Mn4+ (KLSFM, x = 4%, 6%, 8%, 10%, and 12%) for LED lighting were synthesized by an ion-exchange method at room temperature. Among these phosphors, the KLSFM (8 mol%) sample exhibits the strongest excitation in the blue region and emission in the red region. The corresponding translucent fluorescent sheet prepared by the pressure method shows similar luminescent properties which are identical to the powders with the strongest absorption at 467 nm and narrow emission around 632 nm. The fluorescent sheet offers high transmittance in UV–Vis region (close to 100% beyond 550 nm) and better thermal stability and color stability. For comparison, the white pc-LEDs based on the KLSFM (8 mol%) phosphor and fluorescent sheet all emit intense white light with an ideal color rendering index (CRI >93) and a good correlated color temperature (CCT <3500 K). However, the white pc-LED based on the fluorescent sheet have more advantage in application for high-power devices. Working at 200 mA, the LED fabricated with the translucent sheet still keeps excellent performance with a high CRI of 90.1 and a low CCT of 3874 K. The working temperature for this device is only 90 °C after working for 40 min, which is lower than that of the device with the KLSFM (8 mol%) powder, furtherly proving that the translucent sheet has excellent heat dispersion. Therefore, the KLSFM (8 mol%) translucent sheet could be used for high-power pc-LEDs as a red component. [ABSTRACT FROM AUTHOR]

Red-emitting Mn4+-doped fluoride phosphors are recognized as promising materials for high-performance warm white light-emitting diodes (WLEDs). However, the extensive use of toxic hydrofluoric acid in traditional synthesis methods hinders their development and commercialization. Furthermore, the traditional solid-phase method often has cumbersome sintering steps, high temperature, long holding time, and certain safety hazards, so it is very necessary to develop a green synthesis method with simple steps and low energy consumption. In this study, a low-temperature solid-state method is proposed to synthesize Rb A SiF 6 :Mn4+ (A = K, Cs) phosphors by one step. Optimal emission intensities were observed at Mn4+ concentrations of 1.2 % in RbKSiF 6 and 2.1 % in RbCsSiF 6. These phosphors demonstrated high thermal stability. At 423 K, the photoluminescence intensities of RbKSiF 6 :1.2 %Mn4+ and RbCsSiF 6 :2.1 %Mn4+ reached 114 % and 87 % of their respective values at room temperature. Meanwhile, the chromaticity shifts were almost negligible, and high color purity was achieved for both phosphors. The electro-optical performance of WLED devices utilizing these phosphors, in combination with YAG:Ce3+ and GaN chips, showed high color rendering indices (CRI) and low correlated color temperatures (CCT) across varying currents. Specifically, under a driving current of 20 mA, the device incorporating RbKSiF 6 :1.2 %Mn4+ exhibited a CRI of 94 and a CCT of 3732 K, with a luminous efficacy of 61 lm/W. These findings highlight the potential of green-synthesized RASFM phosphors in advancing the application of warm WLEDs. [Display omitted] • A low-temperature solid-state method without HF is used to prepare red phosphors. • Rb A SiF 6 :Mn4+ phosphors shows highly luminescent efficiency and thermal stability. • The LED incorporating RbKSiF 6 : Mn4+ exhibited a CRI of 94 and a CCT of 3732 K. [ABSTRACT FROM AUTHOR]

• Rb 2 LiMF 6 :Mn4+phosphors were prepared by the non-equivalent doping of Mn4+. • Rb 2 LiAlF 6 :Mn4+ exhibits a ultra-intense zero phonon line, due to the low symmetry. • The lower 2E energy of Mn4+in Rb 2 LiMF 6 is realized by the introduction of Li+. • High-quality white LEDs were fabricated with Rb 2 LiMF 6 :Mn4+phosphors. Herein, Rb 2 LiMF 6 :Mn4+ (M= Al, In) phosphors were prepared by the non-equivalent doping of Mn4+. Mn4+ in Rb 2 LiAlF 6 exhibits an ultra-intense zero phonon line (ZPL) detected at 627 nm, due to the highly-distorted symmetry. In contrast, the ZPL at 625 nm for Rb 2 LiInF 6 :Mn4+ is very weak. The 2E energy of Mn4+in Rb 2 LiAlF 6 (15,949 cm−1) is lower than that in all reported fluoride phosphors, which may be ascribed to the stronger polarization effect of Li+. Compared with Rb 2 LiInF 6 :Mn4+ (5.07 %), Rb 2 LiAlF 6 :Mn4+ (6.33 %) has a high internal quantum efficiency (IQE) values of 69.8 % and excellent thermal stability. The white LED packaged with Rb 2 LiAlF 6 :Mn4+ (6.33 %) exhibits perfect performances with a high color render index (CRI = 92.3) and low color temperature (CCT =3875 K) as well as a high luminous efficiency (LE = 97.1 lm/W). Therefore, this work provides a promising red-emitting phosphor for high-quality white LEDs. A red-emitting phosphor Rb 2 LiAlF 6 :Mn4+ with an ultra-intense zero phonon line was designed and prepared for high-quality white LEDs. [Display omitted] [ABSTRACT FROM AUTHOR]

A new red-emitting phosphor based on polyfluoride Na3Li3Sc2F12 doped with Mn4+ was prepared via a co-precipitation method at room temperature. Its crystal structure, luminescence properties and applications are discussed in detail. The as-synthesized phosphor emits red light with intense zero-phonon line (ZPL) at 618 nm under the excitation of 461 nm light. A higher energy of the 2Eg level of Mn4+ was observed in Na3Li3Sc2F12:Mn4+. The Racah parameters B and C were calculated to be 604 cm−1 and 3840 cm−1, respectively. The as-obtained Na3Li3Sc2F12:Mn4+ (4.86 mol%) shows a high internal quantum efficiency (IQE) of 66.8% and better resistance to thermal quenching. A white light-emitting diode (w-LED) with a high color rendering index of 92 and a low color temperature of 3694 K was fabricated. Hence, Na3Li3Sc2F12:Mn4+ as a new red-emitting phosphor has great potential application in w-LEDs. [ABSTRACT FROM AUTHOR]

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]

• NIR emitting A 2 KAlF 6 :Cr3+ phosphors were prepared by a co-precipitation method. • A 2 KAlF 6 :Cr3+ phosphors exhibit broad NIR emission with high quantum efficiencies. • The phosphors have excellent thermal stability of luminescence. • The full-spectrum WLEDs based on A 2 KAlF 6 :Cr3+have good photoelectric performances. Herein, NIR A 2 KAlF 6 :Cr3+ (A = Rb, Cs) phosphors prepared by a co-precipitation method exhibit broad excitation in the blue region and broad NIR emission with high quantum efficiencies (64% for Rb 2 KAlF 6 :0.025Cr3+, and 60% for Cs 2 KAlF 6 :0.02Cr3+). Furthermore, Rb 2 KAlF 6 :Cr3+ and Cs 2 KAlF 6 :Cr3+ phosphors maintain 95.3% and 90.2% of their room-temperature initial intensity at 150 °C, respectively. The full-spectrum white light-emitting diode (WLED) based on Rb 2 KAlF 6 :Cr3+ exhibits a high color-rendering index (94.8), a high luminous efficiency (99.5 lm/W), and a low correlation color temperature (3666 K). The results reveal that these phosphors can not only apply in full-spectrum illumination but also provide new in-depth insights into the design of NIR phosphors with high efficiency and thermal stability. Near-infrared A 2 KAlF 6 :Cr3+phosphors with high thermal stability and quantum efficiency were designed and prepared for fabricating high-performance full-spectrum white light-emitting diodes. [Display omitted] [ABSTRACT FROM AUTHOR]

• A novel oxyfluoride phosphor Cs 3 V 2 O 2 F 7 :Mn4+ was obtained via a facile route. • Red emission of the phosphor exhibits an red-shift compared with fluoride samples. • Cs 3 V 2 O 2 F 7 :Mn4+ exhibits excellent PL properties and ultra-high thermal stability. • A white LED with Cs 3 V 2 O 2 F 7 :Mn4+has good photoelectric performances. Thermal stability is an important parameter of phosphors for high-power LEDs. Herein, we have successfully designed and constructed a novel oxyfluoride phosphor Cs 3 V 2 O 2 F 7 :Mn4+ (CVOF:Mn4+) with a hexagonal structure. Due to its weaker crystal-field and intensive covalency for Mn4+, both excitation and emission of Mn4+ in CVOF:0.15Mn4+have an obvious red-shift in contrast to classical fluoride phosphors. Moreover, CVOF:0.15Mn4+has extremely good thermal stability and its integral emission intensity at 140 °C is 1.77 times higher than the initial value, which meets the requirement of high-power LEDs. A white LED assembled with CVOF:0.15Mn4+and Y 3 Al 5 O 12 :Ce3+ (YAG) exhibits good photoelectric performances with the color correlated temperature of 5127 K and the color rendering index of 89, showing that CVOF:0.15Mn4+could be used as a red component for white LEDs. A new oxyfluoride phosphor Cs 3 V 2 O 2 F 7 :Mn4+ exhibits intense red emission and ultra-high thermal stability for white LEDs [Display omitted] [ABSTRACT FROM AUTHOR]

High-efficiency narrow-band red phosphor plays a profound part in stimulating illumination quality for white light-emitting diodes (WLEDs). In this work, a series of novel double-perovskite Rb 2 KInF 6 :Mn4+ red phosphors was successfully prepared by using a facile co-precipitation technique. The crystallization, particle morphology, photoluminescence properties, and thermal quench behavior of the as-synthesized powder samples were investigated systematically. During the illumination with blue (λ max = 468 nm) and ultraviolet light (λ max = 370 nm), the prepared Rb 2 KInF 6 :Mn4+ phosphors emited a series of narrowband red signals in the range 590–660 nm with strong zero-phonon line (ZPL) emission. Meanwhile, the optimum Mn4+ concentration of at the 2E g →4A 2g transitions was also studied. Moreover, the fluorescence decay lifetimes of the prepared Rb 2 KInF 6 :Mn4+ products were milliseconds. Finally, by coating Rb 2 KInF 6 :Mn4+ with commercially yellow Y 3 Al 5 O 12 :Ce3+ (YAG:Ce3+) phosphors on the commercially available InGaN blue chip, the intense warm white light with suitable correlated color temperature (CCT, 3491 K) and high color-rendering index (R a , 85.1) can be manufactured at a driving current of 20 mA. All of these consequences point out that the novel double-perovskite red-emitting Rb 2 KInF 6 :Mn4+ phosphors are promising in the perspective of WLEDs applications. An efficient novel Rb 2 KInF 6 :Mn4+ phosphor with double - perovskite structure were synthesized via a simple co-precipitation method, which was capable to be fabricated for warm WLEDs. [Display omitted] • A novel Mn4+-activated Rb 2 KInF 6 double-perovskite red phosphor was fabricated by a facile co-precipitation approach. • The resulted phosphor can be efficiently excited by blue light, presenting narrow-band red light emission. • A white LED lamp with high R a (85.1) and low CCT (3491 K) was manufactured with Rb 2 KInF 6 :Mn4+. [ABSTRACT FROM AUTHOR]

A series of naphthyl-modified graphitic carbon nitride were prepared by using melamine, cyanuric acid as precursors and 6-(naphthalen-2-yl)-1,3,5-triazine-2,4-diamine as a molecular dopant. When their mass ratio was 20:20:1, the product (g–C 3 N 4 –Naphth 20:20:1) showed the best photoluminescence performances. The emission spectrum of g–C 3 N 4 –Naphth 20:20:1 was mainly at 410–650 nm and much wider than that of bulk g-C 3 N 4 (mainly at 410–550 nm), relative to bulk g-C 3 N 4 , the maximum emission wavelength (λ em,max) changed from 455 nm to 485 nm, the light color correspondingly changed from deep blue to blue-green, the PL efficiency increased from 5.1% to 11.3%. Excited by ultraviolet chips (λ em,max = 365 nm), a series of LEDs using g–C 3 N 4 –Naphth 20:20:1 blended in epoxy resin at 4.0 wt% together with red-emitting SrAlSiN 3 :Eu2+ at x wt-% (x = 0.08, 0.12, 0.16, and 0.20) as phosphors were fabricated. When x = 0.08, 0.12, 0.16, the LEDs emitted neutral white light, their correlate color temperatures (CCT) were 5277 K, 4602 K and 3794 K, color rendering indexes (CRI) were 85.4, 88.1 and 79.7, respectively. When x = 0.20, it was a warm white LED, its CCT was 3312 K and CRI was 83.3. The results suggested the naphthyl-modified g-C 3 N 4 can be used as efficient metal-free phosphors for LEDs. Blue-green-emitting naphthyl-modified graphitic carbon nitride (g–C 3 N 4 –Naphth) were prepared and used as phosphors in white LEDs. [Display omitted] • A series of naphthyl-modified g-C 3 N 4 were prepared. • The luminescent color changed from deep blue to blue-green after naphthyl modification. • The PL efficiency changed from 5.1% to 11.3% after naphthyl modification. • The naphthyl-modified g-C 3 N 4 was successfully used as phosphors in white LEDs. [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]

• 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]

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]

In this work, we present a novel single-phase red phosphor of Cs 2 NaAlF 6 :Mn4+ with two Al3+ lattice sites, which shows two groups of vibrational phonon sidebands and ultra-intense zero phonon line (ZPL) under blue light illumination. The evidences have shown that the interesting spectral features originate from the non-equivalent occupation of Mn4+ for both Al3+ sites, which induces the neighboring cation vacancies surrounding Mn4+ and highly distorted [MnF 6 octahedral in the Cs 2 NaAlF 6 host. The luminescent behavior of double sites occupied by Mn4+ can absorb researchers' interest on novel red-emitting phosphors. Profiting from the photoluminescence (PL) features, superior color rendering index of R a = 90.3, R 9 = 81, and low correlated color temperature of T c = 3967 K are achieved from white light-emitting diode (LED) by using yellow Y 3 Al 5 O 12 :Ce3+ (YAG) and red Cs 2 NaAlF 6 :Mn4+ phosphors as blue light converters. These results suggest that Cs 2 NaAlF 6 :Mn4+ for phosphor has a stupendous potential for LED lighting. A novel red phosphor of Cs 2 NaAlF 6 :Mn4+ with unprecedented spectral features of double vibrational phonon sidebands and ultra-intense ZPL comparable to the sharpest v 6 peak under blue light excitation was obtained. The amazing spectral feature is originated from the non-equivalent occupation of Mn4+ for both Al3+ sites in CNAF host. Profiting from the extraordinary PL properties, excellent optical performance of CNAF:Mn as color converter is achieved, implying its potential application in white LED lighting or display devices. Image 1 • A novel red-emitting phosphor of Cs 2 NaAlF 6 :Mn4+ has been successfully synthesized. • The crystal structure of Cs 2 NaAlF 6 :Mn4+ has been confirmed. • The spectral feature with ultra-intense zero phonon line has been elucidated. • Double sites occupancy of Mn4+ in Cs 2 NaAlF 6 has been verified. [ABSTRACT FROM AUTHOR]

One new kind of red-emitting oxyfluoride phosphors Rb 2 WO 2 F 4 doped with different Mn4+ contents were synthesized via a facile co-precipitation method at an ambient condition. Meanwhile, the luminescent behaviors of Mn4+ in Rb 2 WO 2 F 4 were investigated in detail. The sample prepared with the WO 3 /K 2 MnF 6 molar ratio of 40:1 has a broad excitation band around 465 nm and emits a series of sharp-emitting peaks around 631 nm. The crystal-field strength D q as well as Racah parameters B and C were calculated to be 2151, 583 and 3872 cm−1, meaning that Mn4+ in Rb 2 WO 2 F 4 experiences a strong crystal field. The luminescence decay time was also determined to be 2.15 ms. Finally, a warm white LED was obtained using Rb 2 WO 2 F 4 :Mn4+ as red component. It's color rendering index was improved to 81.4 and color temperature was decreased to 3588 K. Image 1 • New red phosphor Rb 2 WO 2 F 4 :Mn4+ was synthesized by facile co-precipitation method. • Rb 2 WO 2 F 4 :Mn4+ yields narrow-band emission around 631 nm. • The optimum concentration of Mn4+ has been confirmed to be about 11 mol%. [ABSTRACT FROM AUTHOR]

A novel red-emitting phosphor K 2 [MoO 2 F 4 ]•H 2 O:Mn4+ prepared by a simple precipitation method emits the intense red light with the high internal quantum efficiency of 86.5% and the high thermal stability of luminescence. A w-LED fabricated with this red phosphor shows intense warm white-light with a high color rendering index of 94, a low correlated color temperature of 3945 K. Therefore, K 2 [MoO 2 F 4 ]•H 2 O:Mn4+ maybe find application on w-LED lighting. • K 2 [MoO 2 F 4 ]•H 2 O:Mn4+ was designed and synthesized by a simple precipitation method. • This phosphor exhibits intense red-emission and high internal quantum efficiency. • This phosphor has the high thermal stability of luminescence. • A w-LED coating this sample has excellent photoelectric performances. A red-emitting phosphor K 2 [MoO 2 F 4 ]•H 2 O:Mn4+ (denoted as KMOF:Mn4+) was designed and synthesized by a simple precipitation method, and its structure and luminescence properties were studied in details. The as-prepared KMOF:Mn4+ phosphors show broad excitation band in the blue-light region. The as-optimized phosphor KMOF:Mn4+ (3.28 mol%) has the strongest red-emission with high internal quantum efficiency of 86.5% among these samples with different contents of Mn4+. Meanwhile, this sample is of the high thermal stability of luminescence. One white light-emitting diode (w-LED) was fabricated by coating KMOF:Mn4+ (3.28 mol%) and Y 3 Al 5 O 12 :Ce3+ on a GaN chip. This w-LED can emit intense warm white-light and show excellent photoelectric performances with a high color rendering index of 94, a low correlated color temperature of 3945 K, and the high luminous efficiency of 150.1 lm/W. Hence, KMOF:Mn4+ (3.28 mol%) could be a promising red phosphor for w-LEDs. [ABSTRACT FROM AUTHOR]