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Luminescent crystals with high efficiency have huge potential in applications for white light-emitting diodes (LEDs). Herein, organic–inorganic hybrid crystals doped with Mn4+, [N(CH3)4]2XF6:Mn4+ (X = Si, Ge, and Ti), were grown under mild conditions. Their crystal structural evolution was confirmed by single-crystal X-ray diffraction at different temperatures. These crystals exhibit intense red emission with a high external quantum efficiency (73.0% for [N(CH3)4]2TiF6:Mn4+) and good thermal stability. The warm white LEDs were fabricated by combining these red-emitting phosphors with a YAG:Ce3+ ceramic chip. As-grown crystals can significantly optimize the performances of white LEDs (colour rendering index up to 95). Hence, this work provides a new strategy to explore Mn4+-activated organic–inorganic hybrid materials for white LEDs. [ABSTRACT FROM AUTHOR]

In this study, an efficient polyfluoride red-emitting phosphor, Cs 3 RbGe 2 F 12 :Mn4+ (denoted as CRGF:Mn), has been synthesized using a simple co-precipitation method. The crystal and electronic structures, spectroscopic properties, and photoluminescence thermal stability of CRGF:Mn have been systematically characterized. The results show that Mn4+ ions experience a strong crystal field and present a series of intense red emission peaks under blue light excitation. Moreover, CRGF:Mn exhibits a high color purity (95.1 %), high internal quantum efficiency (82.4 %), and enhanced photoluminescence thermal stability at 150 °C, with an intensity of 113 % relative to room temperature. A warm white light-emitting diode exhibiting a low correlated color temperature (3572 K), high color rendering index (90.7), and suitable luminous efficiency (132.6 lm/W) was prepared using CRGF:Mn as a red component, demonstrating viable application in solid-state lighting. • Synthesis of CRGF:Mn polyfluoride red phosphor with a high internal quantum efficiency (82.4 %). • CRGF:Mn exhibits outstanding photoluminescence thermal stability (113 % at 150 °C). • The application prospect of CRGF:Mn for indoor lighting have been elaborated. [ABSTRACT FROM AUTHOR]

The far-red light around 730 nm plays an important role during the plant growth. Herein, broadband far-red LiMgAlF 6 :Cr3+ phosphors were successfully prepared via the hydrothermal method. Under 424 nm excitation, LiMgAlF 6 :0.05Cr3+ exhibits an emission band peaking at 734 nm with a full-width at half maximum (FWHM) of 131 nm, due to the emission from two kinds of Cr3+. Moreover, the broad band could match well with the absorption spectrum of the plant's P FR. The phosphor not only owns a high internal quantum efficiency (IQE) of 45.6%, but also a good resistance towards to thermal quenching. Its emission intensity at 150 °C is 93.9% of the initial intensity at room temperature. Finally, the LiMgAlF 6 :Cr3+ powder was combined with a 460 nm blue chip to form one LED device, which was carried out on the growth of the tomato plants. The LED based on LiMgAlF 6 :Cr3+ can promote the growth of tomato plants, indicating the feasibility of phosphors for the plant-growth lighting. [Display omitted] • A far-red LiMgAlF 6 :Cr3+ phosphor exhibits broad emission from double sites of Cr3+. • The phosphor owns a high quantum efficiency and good thermal stability. • The LED based on LiMgAlF 6 :Cr3+ can promote the growth of tomato plants. [ABSTRACT FROM AUTHOR]

In this research, the high quality Dy3+, Na+:PbGa 2 S 4 single crystal was grown by Bridgman method. The crystal devices with high transmittance were successfully processed. The crystal structure and crystallization property were characterized by the XRD and XRC patterns. The transmission spectrum, temperature-dependent emission spectrum from 77 K to 350 K and decay curves at room temperature of crystal were measured. The strong absorption at 1315 nm of 6H 15/2 → 6F 11/2 +6H 9/2 transition could match well with high power 1310 nm semiconductor laser. The spectroscopic parameters were calculated by Judd-Ofelt theory based on the absorption spectra. The fluorescence lifetime of 6H 11/2 energy level was fitted to be 2.09 ms and the corresponding fluorescence quantum efficiency η was calculated to be 77%. The emission cross-section at 4325 nm of 6H 11/2 → 6H 13/2 transition was also calculated to be 0.9 × 10−20 cm2. The experiment results show the advantage of Dy3+, Na+:PbGa 2 S 4 crystal in emitting mid-infrared lasers. • High-quality Dy3+,Na+: PbGa 2 S 4 crystal devices were prepared using pressure-resisted and crucible-capsule Brigdman technique 3. • The spectroscopic parameters of Dy3+,Na+: PbGa 2 S 4 were calculated in detail by J-O theory. • The fluorescence emission spectrum and lifetime of Dy3+,Na+: PbGa 2 S 4 crystal at 4325 nm were measured. [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]

• 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]

In this paper, a single-phase red-emitting phosphor BaGaF 5 :Mn4+ (BGFM) was synthesized by a hydrothermal method, and its crystal structure and luminescence properties were studied in detail. The results show that the excitation spectra of BGFM samples are mainly composed of two bands located at the near-ultraviolet and blue light region, respectively, while the emission spectra show multiple peaks in the red region. Due to the defects generated with the non-equivalent occupation of Ga3+ by Mn4+, the adjacent [MnF 6 ] octahedron is highly distorted, resulting in a strong zero-phonon line (ZPL, 627 nm) in the emission spectrum. Additionally, the materials have shown a high internal quantum efficiency (QE = 63.7%) and good color stability. Finally, a white LED was obtained by mixing BGFM and commercial Y 3 Al 5 O 12 :Ce3+ yellow phosphor on a blue light-emitting diode (LED) chip. [Display omitted] • New red phosphor BaGaF 5 :Mn4+ was synthesized by f a hydrothermal method. • The [MnF 6 ] octahedron is highly distorted, resulting in a strong zero-phonon line. • The lower 2E level energy (15949 cm−1) of Mn4+ was observed in BaGaF 5 :Mn4+. [ABSTRACT FROM AUTHOR]

• Cs 2 KGaF 6 :Mn4+ phosphor with high EQE of 43% was systhesized via co-participated methods. • DFT calculation reveals [MnF 6 ]2- occupied [GaF 6 ]3- and produce a V Cs ′ vacancy to balance the charge mismatch. • Unequivalent doping strategy provides detailed insights into the local structure of Mn4+ substituted in fluorides. • Cs 2 KGaF 6 :Mn4+ phosphor is suitable for wide color gamut displays. [Display omitted] Narrow-band red-emitting phosphors are worth investigating and developing to enhance their luminescence efficiency for white light-emitting diodes (WLEDs) and broaden the color gamut of backlight displays. Herein, a novel red-emitting fluoride phosphor Cs 2 KGaF 6 :Mn4+ (CKGFM) was synthesized, which presents sharp red emission bands, short fluorescence lifetime (τ = 3.81 ms) and high external quantum efficiency (EQE = 43%). To better understand Mn4+ incorporation in CKGFM, density functional theory (DFT) energetic calculations were performed to compare the charge compensation probabilities of an Mn4+ substituted at a Ga3+ or K+ site. The temperature-dependent luminescence trend shows that the CKGFM phosphor has good thermal stability in the temperature range of 15–120 ℃, indicating its potential in backlight LEDs. The as-prepared CKGFM phosphor was used to fabricate one white light-emitting diode (WLED) with β-SiAlON:Eu2+ green phosphor and blue InGaN LED chip, which shows a high luminous efficiency of 106.30 lm∙W−1 and a National Television Standards Committee (NTSC) value of 114.6%. The present study provides detailed insights into the local structure of Mn4+ substituted in fluoride red-emitting phosphors and helps to realize better Mn4+ emission for WLEDs. [ABSTRACT FROM AUTHOR]