Search

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]

A yellow-emitting cationic iridium(III) complex [(dfppy)2Ir(TBD)]PF6 (TBD: N4,N4′-bis(3-(triethoxysilyl)propyl)-[2,2′-bipyridine]-4,4′-dicarboxamide; dfppy: 2-(2,4-difluorophenyl)pyridine) containing hydrolysable alkoxysilanes was synthesized. Then, a series of silica-based hybrid nanospheres with diameters of around 400 nm was prepared via the hydrolysis of this complex together with tetraethyl orthosilicate (TEOS, a silica source). When the amount of the complex used was 5.0 wt%, hybrid nanospheres showed the best photoluminescence (PL) properties, relative to the PL quantum yield of pure solid [(dfppy)2Ir(TBD)]PF6 (12.7%), that of hybrid nanospheres increased to 26.2%. Moreover, the thermal decomposition temperature (Td) of pure solid [(dfppy)2Ir(TBD)]PF6 was 331 °C, the Td of the complex in hybrid nanospheres increased to 447 °C. However, the yellow light emission was almost unchanged and was still located at 500–750 nm with a maximum wavelength (λem,max) of 577 nm. Under the excitation of blue-emitting chips (λem,max ≈ 455 nm), cold/neutral/warm white light-emitting diodes (WLEDs) with good luminous quality can all be fabricated using these hybrid nanospheres as phosphors in epoxy resin at different blending concentrations. Compared with two or three iridium(III) complexes being contained in silica-based particles as phosphors as described in literatures, in this study, silica-based hybrid nanospheres covalently containing only one yellow-emitting cationic iridium(III) complex as phosphors provide a more effective and simpler method for preparation high-performance WLEDs. [ABSTRACT FROM AUTHOR]

Red phosphors K2XF6:Mn4+ (X: Si, Ti, Ge) are precipitated from a 40% aq. [ABSTRACT FROM AUTHOR]

In this work, a series of Cr3+-doped A2NaYF6 (denoted as ANYF:Cr; A = K, Rb, and Cs) fluoroyttrate double-perovskites with broad blue excitation and near-infrared (NIR) emission bands were prepared using a high-temperature solid-state reaction method. The physicochemical and spectroscopic properties of the as-prepared products, including crystal structure, bandgap, morphology, luminescence behaviour and optical performance, were studied in detail. The results show that the Cr3+ activators undergo a decreasing crystal field in ANYF in the direction from K to Cs, yielding a red shift of the emission peak position from 758 to 786 nm, whilst the full-width-at-half-maximum (FWHM) expands from 98 to 104 nm. By virtue of the broadband NIR emission, clear structural images of the tangerine section, mini LED flashlight and circuit board were obtained by merging the optimal RNYF:Cr phosphor on a blue InGaN chip, implying its potential use in light-emitting diodes for non-destructive testing. [ABSTRACT FROM AUTHOR]

The non-equivalent doping of Mn4+ in red-emitting fluoride phosphors effectively shortens the fluorescence lifetime. Herein, we successfully synthesized Rb2NaInF6:Mn4+ phosphors by an ion-exchange method. The compensation mechanism of Mn4+ local symmetry and charge balance in the phosphor were studied in detail by theoretical calculations based on density functional theory. The phosphor Rb2NaInF6:Mn4+ (5.59 mol%) exhibits intense red emission with a short fluorescence lifetime (1.45 ms). Meanwhile, it has excellent colour stability and thermal quenching stability at elevated temperatures. Using Rb2NaInF6:Mn4+, β-SiAlON:Eu2+ and a blue-emitting GaN chip as red, green, and blue components, the white light-emitting diode (w-LED) exhibits a wide colour gamut of 94.1% of the National Television System Committee (NTSC) standard value. So, this work provides valuable information to investigate novel red-emitting fluoride phosphors for LED backlighting. [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 exploration of Cr3+-doped near-infrared (NIR) phosphors for light-emitting diodes has attracted widespread attention. In this work, we present a fluoride double perovskite K 2 LiScF 6 :Cr3+ NIR-emitting phosphor through a co-precipitation method. It was found that the Cr3+ activators undergo a weak crystal field and present a NIR emission band peaking at 768 nm under blue light excitation (430 nm). Meanwhile, the K 2 LiScF 6 :Cr3+ exhibits a high activation energy (0.537 eV), a weak electron-phonon coupling (EPC) effect and a remarkable photoluminescence thermal stability at 423 K, with an intensity of 95.1% of that at room temperature. Profiting from the luminescent properties, clear night vision images and human palm vein photographs were realized by coating the K 2 LiScF 6 :Cr3+ phosphor on a blue InGaN chip and using it as a lighting source, suggesting its applicability in light-emitting diodes for NIR spectroscopy applications. • A novel near-infrared phosphor of K 2 LiScF 6 :Cr3+ has been synthesized. • The low thermal quenching behavior of Cr3+ in K 2 LiScF 6 host was verified. • The applications of K 2 LiScF 6 :Cr3+ for night vision and vein imaging were evaluated. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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 thiourea loading strategy was proposed to modify KSF phosphor. • The excellent water resistance was obtained after thiourea treatment. • The degradation and restore mechanisms of T-KSF phosphor was revealed. Recently, Mn4+ doped fluoride phosphors have been considered as ideal candidate materials employed in white light-emitting diodes (WLEDs). However, the extremely serious performance deterioration in a wet environment has affected their practical commercial applications. Herein, we developed a novel thiourea loading strategy for greatly improving the moisture resistance of typical K 2 SiF 6 : Mn4+ (KSF) red phosphors through treated by thiourea ethanol solution evaporation. The luminescent properties and moisture resistance have been discussed in detail, and the underlying moisture resistance mechanism was further proposed. The results show that the moisture resistance of KSF phosphor treated by thiourea significantly increased approximately sevenfold than that of untreated counterpart, exhibiting a potential application in the WLEDs backlight with high gamut display. These works brings up a promising alternative strategy for enhancing moisture resistance and provides a deeper understanding on the performance degradation mechanism for a variety of Mn4+ doped fluoride phosphors system. [Display omitted] [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]

Herein, a new red-emitting phosphor, Na 3 TaF 8 :Mn 4+ , was synthesized by non-equivalent doping of Mn 4+ under mild condition. Its crystal structure and morphology were characterized by the powder X-ray diffraction (XRD), scanning electron microscopy (SEM). This sample is of single phase with monoclinic crystal structure. Mn 4+ might occupy the site of Ta 5+ in Na 3 TaF 8 , being located at the center of uniquely tetragonal anti-prism coordinated by eight F - . The as-prepared Na 3 TaF 8 :Mn 4+ has sharp red emissions with higher color purity under the blue light excitation. The luminescent behavior of Mn 4+ in such host is similar with that in some hexafluorides with disordered octahedral structure. Intense red light can be observed from the single red LED based on Na 3 TaF 8 :Mn 4+ . These results show this phosphor to be a potentially red component for LED backlighting. [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]

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]

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]

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]

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 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]

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]

• 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]

• Commercial air-laid paper and carbon ink were used for moist power generation. • The voltage of 0.35 V and current of 33.9 μA were generated in the atmosphere (6 cm2). • The power generator was designed for some extreme situations such as in the wild. • Integration of generators could power wearable electronic devices in the atmosphere. Low-grade energy harvesting from the ambient environment promises to relieve the energy shortage in the remote regions or emergency needs. The reported materials employed for low-grade energy harvesting requires costly raw materials and highly technical skills, hindering the applications in isolated regions or after natural disasters. Herein, we report the use of commercial air-laid paper and carbon ink to harvest electrokinetic energy in the capillary flow. The paper-based electrokinetic power generator with size of 6 cm × 1 cm could continuously generate an output voltage of 0.35 V and current of 33.9 μA in the ambient condition (20 °C and 50% Relative Humidity). The output power could maintain for over 120 h. When connected in series and in parallel, the power generator with excellent flexibility could power some common electronic devices in the atmosphere, such as light-emitting diode, electronic calculator and watch. This work offers a rational approach to employing low-cost materials for ambient energy harvesting, thus advancing the application in portable and wearable electronic devices. [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 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]

Cs2GeF6:Mn4+ is prepared by cation exchange through addition of K2MnF6 and CsF to a GeO2 solution in HF (40 wt.%). [ABSTRACT FROM AUTHOR]

Mn4+-doped Na2MF6 (M: Si, Ge, Ti) is prepared by dissolving MO2 in HF (40%) and adding NaMnO4 to the transparent solution followed by co-precipitation with NaF (70 °C, 30 min). [ABSTRACT FROM AUTHOR]