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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]

The development of anode materials with high theoretical capacity and cycling stability is very important for the electrochemical performance of lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Herein, SnSe/NC hollow nanospheres with different crystal orientations were prepared by regulating the high-temperature selenization of the PDA@SnO2 precursor for lithium/sodium storage. In SnSe/NC hollow nanospheres, the physical buffering and chemical bonding of the nitrogen carbon matrix and SnSe nanoparticles could inhibit volume expansion and polyselenide loss, thus maintaining long-term structural stability. More importantly, electrochemical tests and DFT calculations show that the diffusion energy barrier of Li+/Na+ is significantly reduced at the SnSe (400) rather than the usual (111) facet, which is conducive to the uniformity of ion insertion into SnSe, thus effectively enhancing the reaction kinetics and reversibility of lithium/sodium storage. Therefore, SnSe/NC hollow nanospheres with rich SnSe (400) and good dispersion formed at 550 °C delivered the best reversible specific capacity and rate performance. After a long period of 900 cycles, the capacity retention of lithium/sodium ion batteries is close to 84.88% and 77.05%, respectively. Our findings provide valuable insights into the design of metal selenides for advanced LIBs/SIBs. [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 work, we present a brand-new narrowband red-emitting fluoroperovskite via the introduction of Mn4+ into NaZnF3 through a facile co-precipitation method at room temperature. The physicochemical properties of the fluoroperovskite such as crystal and electronic structures, morphology, and elemental composition, as well as its spectroscopic properties such as luminescence behaviours and optical performance were characterized and investigated in detail. Evidence shows that NaZnF3:Mn4+ exhibits a uniform particulate shape with single-phase crystallinity. By virtue of the non-equivalent substitution and the [MnF6] octahedral distortion in the fluoride host, sharp red emissions of phonon sidebands and the zero-phonon line upon blue light excitation are identified. Benefiting from the unique spectral feature, a wide colour gamut of 104.1% NTSC is achieved by coating β-SiAlON:Eu2+ and NaZnF3:Mn4+ on an InGaN chip, indicating the potential use of the Mn4+ fluoroperovskite as a colour converter for display backlight application. [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]

A series of APF6:Mn4+ (A = Cs+, Rb+, K+) phosphors with single phases were obtained via a simple ion exchange method. These phosphors can exhibit red emission with a broad excitation band in the blue region. The optimized concentration of Mn4+ in APF6:Mn4+ was determined. The Racah parameters B and C of Mn4+ in APF6:Mn4+ were also calculated. The results indicate that Mn4+ in CsPF6:Mn4+ experiences the weakest crystal field among APF6:Mn4+. The phosphor CsPF6:Mn4+ prepared with the HPF6/K2MnF6 molar ratio of 10 : 1 has the strongest red emission and the highest external quantum efficiency of 50.4% among the samples. It has high thermal quenching resistance and its emission intensity at 160 °C is about 1.1 times higher than that at room temperature. This sample also can remarkably improve the color rendering index and decrease the colour rendering index of white light-emitting diodes (w-LEDs). Hence, CsPF6:Mn4+ could be used as a red-emitting phosphor for warm w-LEDs. [ABSTRACT FROM AUTHOR]

New red-emitting phosphors A2HfF6:Mn4+ (A = Rb+, Cs+) with a single phase have been successfully synthesized via a simple ion exchange method, and their structures and luminescence properties were investigated. It was found that Mn4+ ions in Rb2HfF6 and Cs2HfF6 who share wide band gaps can possess broad excitation bands in the blue regions and intense red emission with internal quantum yields of 0.556 and 0.652, respectively. Meanwhile, these red phosphors exhibit high chemical and thermal stabilities. A series of LED devices with a tunable color rendering index and color temperature were fabricated with these samples which can remarkably optimize the optical performances of white light-emitting diodes (w-LEDs). These results indicate that A2HfF6:Mn4+ phosphors can be promising red phosphors in w-LEDs. [ABSTRACT FROM AUTHOR]

A single-phased Mn4+ doped fluorozirconate red phosphor, K3ZrF7:Mn4+, has been successfully synthesized. Its structure, morphology, composition and optical properties were investigated by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic absorption spectroscopy, diffuse reflectance spectroscopy, photoluminescence spectroscopy and by using luminescence decay curves. It was found that Mn4+ ions only coordinating with seven F− anions in a K3ZrF7 crystal field can possess intense red emission under blue light illumination. Mixing the obtained K3ZrF7:Mn4+ red phosphor with commercial Y3Al5O12:Ce3+ and coating the mixture on a blue-GaN chip, obvious warm white light with a low correlated color temperature (2970 K) and a high color rendering index (Ra = 91.4 and R9 = 72) were achieved from white light-emitting diode devices. [ABSTRACT FROM AUTHOR]

Correction for 'Red-emitting phosphors APF6:Mn4+ (A = Cs+, Rb+, K+): synthesis, luminescence properties and application in solid-state lighting' by Yu Chen et al., Dalton Trans., 2019, 48, 10901–10906. [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]

A single-phased Mn4+ doped fluorozirconate red phosphor, K3ZrF7:Mn4+, has been successfully synthesized. Its structure, morphology, composition and optical properties were investigated by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic absorption spectroscopy, diffuse reflectance spectroscopy, photoluminescence spectroscopy and by using luminescence decay curves. It was found that Mn4+ ions only coordinating with seven F− anions in a K3ZrF7 crystal field can possess intense red emission under blue light illumination. Mixing the obtained K3ZrF7:Mn4+ red phosphor with commercial Y3Al5O12:Ce3+ and coating the mixture on a blue-GaN chip, obvious warm white light with a low correlated color temperature (2970 K) and a high color rendering index (Ra = 91.4 and R9 = 72) were achieved from white light-emitting diode devices. [ABSTRACT FROM AUTHOR]