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In recent decades, numerous red phosphors have been designed and developed. Nevertheless, many of them are unsatisfactory due to their low brightness and poor thermal stability. Look at these shortcomings; present study reports on Eu3+ doped Y 2 Si 2 O 7 (YPS) phosphors, synthesized through low temperature based urea assisted gel-combustion method. Comprehensive investigations were conducted on phase purity, luminous characteristics, energy transfer mechanism, quantum efficacy, morphology, elemental makeup, band gap and thermal stability. XRD analysis was employed to verify the preparation of Y 2 Si 2 O 7 matrix with triclinic structure (P-1 space group). Morphology and elemental investigations of the fabricated materials was evaluated via TEM and EDX techniques respectively. Under the illumination at 393 nm, the most strong emission band is shown in PL spectra at 613 nm (electric dipole 5D 0 →7F 2 transition). Additionally, the dipole-quadrupole (d-q) interaction was found to be the predominant route of energy transfer among nearby Eu3+ ions and it was concluded that 3 mol % was the optimal doping concentration of Eu3+ ions. The Judd-Ofelt (J-O) theory was used for current phosphors in order to establish their Ω 2 and Ω 4 with other radiative parameters. The assessment of thermal stability yielded highly promising results with activation energy of 0.241 eV. Present research indicates that Y 2 Si 2 O 7 :Eu3+ is a promising candidate of red emitting phosphor for white light-emitting diodes. [Display omitted] • Gel-combustion derived Eu3+ doped Y 2 Si 2 O 7 nanophosphors were crystallized into triclinic symmetry with P–1 space group. • Dominance of electric dipole 5D 0 →7F 2 transition at 613 nm was observed which define the red color of synthesized nanophosphors. • The luminous thermal stability revealed 69.4 % of luminescence at 498 K with activation energy of 0.241 eV. • Colorimetric investigation of the synthesized Y 2 Si 2 O 7 :Eu3+ nanophosphors validate their applicability in white light applications. [ABSTRACT FROM AUTHOR]

9,9‐Dimethyl‐9,10‐dihydroacridine (DMAC) is one of the most widely used electron donor for constructing high‐performance thermally activated delayed fluorescence (TADF) emitters. However, DMAC‐based emitters often suffer from the imperfect color purity, particularly in blue emitters, due to its strong electron‐donating capability. To modulate donor strength, 2,7‐F‐Ph‐DMAC and 2,7‐CF3‐Ph‐DMAC were designed by introducing the electron‐withdrawing 2‐fluorophenyl and 2‐(trifluoromethyl)phenyl at the 2,7‐positions of DMAC. These donors were used, in combination with 2,4,6‐triphenyl‐1,3,5‐triazine (TRZ) acceptor, to develop novel TADF emitters 2,7‐F‐Ph‐DMAC‐TRZ and 2,7‐CF3‐Ph‐DMAC‐TRZ. Compared to the F‐ or CF3‐free reference emitter, both two emitters showed hypsochromic effect in fluorescence and comparable photoluminescence quantum yields without sacrificing the reverse intersystem crossing rate constants. In particular, 2,7‐CF3‐Ph‐DMAC‐TRZ based OLED exhibited a blue shift by up to 39 nm and significantly improved Commission International de l′Éclairage (CIE) coordinates from (0.36, 0.55) to (0.22, 0.41), while the external quantum efficiency kept stable at about 22.5 %. This donor engineering strategy should be valid for improving the color purity of large amount of acridine based TADF emitters. It can be predicted that pure blue TADF emitters should be feasible if these F‐ or CF3‐modifed acridine donors are combined with other weaker electron acceptors. [ABSTRACT FROM AUTHOR]

A carbazole‐based hole‐transport‐type (p‐type) host, BPhCz, is developed using a nonsymmetrical connection strategy between two identical groups. Two benzimidazole–triazine‐based electron acceptor materials with superior electron transport abilities, namely SFX‐PIM‐TRZ and DSFX‐PIM‐TRZ, are designed to fabricate exciplex‐host systems combined with BPhCz. Exciplexes exhibit excellent carrier transport characteristics and appropriate energy levels and can serve as hosts for green multiple resonance‐induced thermally activated delayed fluorescence (MR‐TADF) devices. Efficient green MR‐TADF organic light‐emitting diodes with high color purity and low efficiency roll‐offs are successfully fabricated using the exciplexes prepared from BPhCz:SFX‐PIM‐TRZ and BPhCz:DSFX‐PIM‐TRZ as hosts, which show low driving voltages of 2.6 and 2.7 V, high maximum external quantum efficiencies (EQEs) of 35.7% and 35.5%, ultrapure green emission with Commission Internationale de L'Eclairage coordinates of (0.27, 0.69) and (0.28, 0.69), and high EQEs of 31% and 30.5% at 1000 cd m−2, respectively. [ABSTRACT FROM AUTHOR]

We are introducing an innovative organic semiconductor electroluminescent device capable of emitting light with unprecedented characteristics, that is, high directionality with divergence angle of 1.1° and high color purity with the full‐width at half‐maximum of 2.5 nm. This achievement was realized through design techniques aimed at enhancing gain via meticulous recombination zone control and complemented by the reduction of the optical losses. These results demonstrate the simultaneous achievement of a narrow spectrum and high directionality in an organic electroluminescent device. [ABSTRACT FROM AUTHOR]

Red fluorescent materials have important application value in the background light and LED lighting fields of displays. In this work, a novel type of rare earth free deep-red phosphor LiMg4SbO7:Mn4+ was prepared successfully, and its crystal structure, microstructure, fluorescence spectrum, quantum yield, thermal stability, fluorescence lifetime, color coordinates and color purity were studied in detail. The excitation spectra of LiMg4SbO7:Mn4+ phosphors are located at 200–600 nm, which can be matched with ultraviolet, near-ultraviolet, and blue-light chips. The exciting result is that the LiMg4SbO7:0.002Mn4+ phosphor exhibits astonishing quantum efficiency, thermal stability and color purity. Finally, the developed LiMg4SbO7:Mn4+ and the yellow phosphor Y3Al5O12:Ce3+ (YAG:Ce3+) were mixed and coated on a blue light chip (460 nm) to produce a w-LED, which exhibited warm white luminescence with color coordinates of (0.3575, 0.3809), correlated colour temperature (CCT) of 4687 K, and color rendering index (CRI) of 83.6. It is reasonable to consider that LiMg4SbO7:Mn4+ phosphors with excellent photoluminescence performance have great application value in LED lighting fields. [ABSTRACT FROM AUTHOR]

In this work, novel Mn2+‐doped transparent NaYP2O7 glass–ceramics were prepared through melt‐quenching and subsequent thermal treatment. The surface crystallization method was confirmed based on the differential scanning calorimeter, X‐ray diffraction, and scanning electron microscope characterization. As the increase and prolong of the heat‐treatment temperature and time, the crystallinity of the NaYP2O7 glass–ceramics increases, while the transmittance gradually decreases. The optimal heat‐treatment regime is identified to be crystallized over 4 h at 580°C based on the crystallinity and transmittance. Under the excitation of 408 nm, both the Mn2+‐doped precursor glass and glass–ceramic crystallized at 580°C for 4 h generate a broad emission at 620 nm (4T2(g)→6A1(s)) with a full width at half‐maximum (FWHM) of ∼107 nm. The glass–ceramics exhibit higher emission intensity and longer decay lifetime than that of precursor glass with the aid of the low phonon energy NaYP2O7 crystals. The Mn2+‐doped glass–ceramic exhibits stable orange‐red luminescence with the chromaticity coordinates of (0.568, 0.428), low correlation color temperature of 1 800 K, high color purity of 98.88%, and low thermal quenching (70% at 373 K of the initial intensity at 298 K). The above results indicate that Mn2+‐doped transparent NaYP2O7 glass–ceramics have promising potential for orange‐red color display devices. [ABSTRACT FROM AUTHOR]

Numerous structural and conductive properties of barium cerate (BC) make this material a promising candidate for energy storage applications. In this work, we demonstrated that BC can be proficiently functionalized by incorporating trivalent samarium ions to give rise to optical properties. Single-phased BaCeO3:Sm3+ (BCS) phosphors were synthesized by gel combustion technique followed by calcination. The crystal structure, optical properties, and prospective applications in LEDs were investigated systematically. By linking the information acquired from the diffuse reflectance spectra with that of the PL spectra, we better understood the electronic level structure and energy transfer mechanism. Fine yellow-orange luminescence with 100% color purity (CP) and lower Correlated Color Temperature (CCT) has been achieved via energization at 348 nm wavelength. The x = 0.02 Sm3+ has been identified as the optimized content for the luminescence with a quantum efficiency of 34.2%. Obtained yellow-orange coordinates (0.564, 0.435) are proximate to commercialized L3 rank amber LED (Nichia corporation). The present results signify that UV light can suitably energize the BCS phosphor to get monochromatic amber light which can be used to guard medications during manufacture and storage. [ABSTRACT FROM AUTHOR]

The hue‐recognition based point‐of‐care diagnosis favorites both human visual perception and imaging analysis with portable terminals. Semiconductor nanoplatelets (NPLs) as an emerging narrow‐emissive fluorophore particularly suit above color‐purity desired diagnosis, but are hindered by their intrinsic hydrophobicity and difficulty in controlled assembly. Here the host‐guest assembling of hydrophobic NPLs are developed within 3D porous space of dendritic templates, and stepwise surface silanization to fabricate silica‐NPLs‐silica structure (SNS). The structure enables high fluorescence of single assembly reaching 246‐fold and 4‐fold brightness of single NPL and commercial europium‐doped polystyrene bead. The strategy is compatible with various colored NPLs (≈540–640 nm emission) and provides stable aqueous colloids with well‐preserved emission. The high brightness and narrow emission of SNS enable both signal amplification and visual/image color discrimination. The hue‐recognizable lateral flow immunoassay for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS‐CoV‐2) nucleocapsid protein reveals an average naked‐eye interpretation accuracy of 92.9% over six concentration levels referring to standard card, accompanied by a quantification linear range of 0.13–200 ng mL−1 and a limit of detection of 0.13 ng mL−1 by smartphone. The diagnostic results for SARS‐CoV‐2 positive clinical samples demonstrate easily distinguishable antigen positive levels based on hue‐gradients, which holds significance for home‐based self‐testing of pathogens. [ABSTRACT FROM AUTHOR]

We present quad-layered reflective structural color filters generating vivid additive primary colors by controlling a mode number in a Fabry–Perot (FP) cavity and an anti-reflective (AR) coating layer, thus accomplishing high spectral contrast which is highly demanded in creating sharp colors. The reflection brightness of fabricated structural color filters is over 78% and a color gamut is comparable to the standard color gamut (sRGB). Higher-order resonant modes are exploited yielding a narrow passband with strong suppression of the reflection at shorter and longer wavelength ranges for a green color, while red and blue colors are produced by employing fundamental resonant modes. Besides, the structural color filters maintain both high brightness and high color purity at oblique incidence angles up to 40° due to a small angle of refraction by a cavity medium with high refractive index. Moreover, a large-scale fabrication is enabled owing to the simplicity of a device structure, where thin film deposition is used. The scheme presented in this work may open the door to a number of applications, such as reflective displays, imaging devices, colored photovoltaics, and decorations. [ABSTRACT FROM AUTHOR]

A series of Eu3-doped strontium pyrophosphate (Sr2P2O7) samples was developed by a combustion synthesis process to investigate their photoluminescence (PL) properties. X-ray diffraction analysis was conducted to identify the creation of an alpha phase with an orthorhombic crystal structure. Bond formation of a pyrophosphate group in the structure of phosphor was recognized through FTIR spectra. The surface morphology of the particles was studied through SEM. The energy band gap of the undoped phosphor was calculated to be 5.04 eV through analysis of diffusion reflectance spectra (DRS), and it gradually changed with doping concentration. The phosphors were excited under NUV–blue light i.e., 396 nm and 466 nm, and displayed prominent red emission at a wavelength of 618 nm. The PL spectra of Eu3+ doped Sr2P2O7 were examined for the dependency of PL intensity on doping ion concentration and excitation energy. The optimum PL intensity was obtained at 0.3% concentration of Eu3+, and intensity quenching was observed with a further increase in concentration. This occurred due to multipolar interaction, which was confirmed through the critical distance Rc value of 12.6 Å. Temperature-dependent PL was recorded under 396 nm excitation for an optimized phosphor (0.3% Eu3+). Reduction in PL intensity was observed at higher temperature, but 82% intensity persisted at 540 K with respect to the intensity attained at room temperature i.e., 300 K. The phosphor has high thermal stability, which is confirmed by the activation energy value of 0.206 eV. The PL emission decay lifetime was determined to be of the order of milliseconds for different concentrations of Eu3+. CIE chromaticity coordinates values were assessed from the PL spectra recorded at 396 nm excitation and the color purity was also determined for all the doped phosphors. The quantum efficiency of the 5D0 level transition was calculated to be 95.5% to 85.5% for all doped samples. The experimental results were further compared with determined Judd–Ofelt parameters. CIE and CCT values for 0.3% Eu3+-doped phosphor were evaluated to be (0.638, 0.364) with color purity of 91.5%. The results obtained for the as-prepared Eu3+-doped Sr2P2O7 phosphor are quite significant for application of the phosphor as a red-emitting phosphor in pc-WLEDs. [ABSTRACT FROM AUTHOR]

Thermally activated delayed fluorescent (TADF) and phosphorescent blue organic light‐emitting diodes (OLEDs) have been developed to overcome the relatively low triplet exciton utilization of traditional fluorescent OLEDs. However, broad emission spectra originating from charge transfer process limit the commercial application of such blue OLEDs. Herein, an effective phosphor‐sensitized fluorescent (PSF) OLED device structure was designed. PSF OLED exhibited a maximum blue index (BI) of 508 cd/A/CIEy with CIEy of 0.060, which has been the highest efficiency result reported for PSF deep‐blue OLEDs. A nearly 100% improvement in operational lifetime LT95 (L/L0 = 95%) was achieved successfully by using lower triplet energy (T1) and deuterated host materials. Impressively, the sensitized OLEDs maintained BI of 407 cd/A/CIEy, narrow emission spectra (FWHM = 17 nm), and high color purity (CIEy = 0.046), revealing the attractive technical advantages and commercial application potential. [ABSTRACT FROM AUTHOR]

High color purity is one of the important features for single‐crystal metal halide perovskite light‐emitting diode (LED). Despite single‐crystal perovskite showing low bulk defect concentration, single‐crystal perovskite LEDs do not exhibit high color purity advantage due to the absence of effective surface defect passivation. Herein, one fully wrapped structure is proposed to passivate the surface of the free‐standing CsPbBr3 single‐crystal films. The surface of CsPbBr3 single‐crystal films is wrapped by ultra‐thin polymethyl methacrylate, precisely controlling the thickness. The single‐crystal perovskite film device can achieve high color purity with a full width at half maximum (FWHM) of 15.8 nm) and a large luminescent area of 2.25 mm2. It is observed that surface passivation is due to interaction of CO bond in polymer chains with the Lewis acid PbBr2. The passivated perovskite single‐crystal films significantly improve carrier lifetime and suppress surface defects. It is noteworthy that the passivated free‐standing single‐crystal perovskite films are feasible to build up a vertical LED device structure, avoiding the edge glowing and short‐circuiting of the LED device. This study demonstrates the large luminescent area of the high‐quality millimetre‐scale free‐standing single‐crystal films for wide color gamut display and vertical optoelectronic devices. [ABSTRACT FROM AUTHOR]

Research into red phosphors with a high color rendering index is particularly compelling, given the absence of a red component in the spectrum of commercial pc-WLEDs, which combine blue LED chips with yellow-emitting YAG:Ce3+ phosphors. Herein, we reported a novel Eu3+ activated Ca3Zn3Te2O12 red-emitting phosphor, synthesized using a conventional high-temperature solid-phase method. The phase and crystal structures were analyzed by powder X-ray diffraction and Rietveld refinement. The optimal excitation peak of the Ca3Zn3Te2O12:Eu3+ phosphor was located at 395 nm, matching those of conventional commercial near-ultraviolet chips. In addition, the Ca3Zn3Te2O12:9%Eu3+ phosphor exhibited good thermal stability, with an activation energy of 0.267 eV, and the CIE color coordinates hardly changed with temperature. Ultimatel, a high-quality white LED device was fabricated by combining Ca3Zn3Te2O12:9%Eu3+ red phosphor, a commercial BaMgAl10O17:Eu2+ blue phosphor, and(Ba,Sr)2SiO4:Eu2+ green phosphor with a 395 nm near-UV chip. Despite a substantial increase in the input current from 20 to 320 mA, the white-LED maintained a stable color rendering index of around 80, highlighting its consistent performance. These results indicated that Eu3+ activated Ca3Zn3Te2O12 phosphors are promising red emission candidates for white LEDs pumped by near ultraviolet chips. [ABSTRACT FROM AUTHOR]

Inkjet printing technology offers a unique approach to producing direct-patterned pixels without fine metal masks for active matrix displays. Organic light-emitting diodes (OLEDs) consisting of thermally activated delayed fluorescence (TADF) emitters facilitate efficient light emission without heavy metals, such as platinum and iridium. Multi-resonance TADF molecules, characterized by their small full width at half maxima (FWHM), are highly suitable for the requirements of wide color-gamut displays. Herein, host-free TADF inks with a low concentration of 1 mg/mL were developed and inkjet-printed onto a seeding layer, concurrently serving as the hole-transporting layer. Attributed to the proof-of-concept of host-free inks printed on a mixed seeding layer, a maximum external quantum efficiency of 13.1% (improved by a factor of 21.8) was achieved in the inkjet-printed OLED, with a remarkably narrow FWHM of only 32 nm. Highly efficient energy transfer was facilitated by the effective dispersion of the sensitizer around the terminal emitters. [ABSTRACT FROM AUTHOR]

Orthogonal three‐color luminescence materials designed based on lanthanide doping multi‐component nano‐systems have exhibited great potential in volume display technology. Previous studies devoted to integrate the different color emitters within a single core‐shell nanoparticle, which suffers complexity in synthesis and difficulty in repeatability. In this work, an alternative is proposed. Three kinds of upconversion nanocrystals (UCNCs) with relatively simple configurations are prepared separately. Each kind of nanocrystals takes charge of emit a specific color upon one particular excitation (i.e., 808, 980, and 1540 nm pumps). Luminescent property of the mixture containing these nanocrystals are investigated. Excitation wavelength driven orthogonal three‐color luminescence property is found in this mixture. With the combination excitation, the emission color can be modulated, covering a gamut with its aera of 110% sRGB, superior to the previous reports. In addition, a quantized strategy to evaluate the orthogonality of the luminescence is also proposed, which will be useful for the further investigation and development of remote‐type controlled luminescent materials. Finally, the demonstration of colored 3D display application is conducted and presented in this work. [ABSTRACT FROM AUTHOR]

Two blue-emitting materials, 4-(12-([1,1′:3′,1″-terphenyl]-5′-yl)chrysen-6-yl)-N,N-diphenylaniline (TPA-C-TP) and 6-([1,1′:3′,1″-terphenyl]-5′-yl)-12-(4-(1,2,2-triphenylvinyl)phenyl)chrysene (TPE-C-TP), were prepared with the composition of a chrysene core moiety and terphenyl (TP), triphenyl amine (TPA), and tetraphenylethylene (TPE) moieties as side groups. The maximum photoluminescence (PL) emission wavelengths of TPA-C-TP and TPE-C-TP were 435 and 369 nm in the solution state and 444 and 471 nm in the film state. TPA-C-TP effectively prevented intermolecular packing through the introduction of TPA, a bulky aromatic amine group, and it showed an excellent photoluminescence quantum yield (PLQY) of 86% in the film state. TPE-C-TP exhibited aggregation-induced emission; the PLQY increased dramatically from 0.1% to 78% from the solution state to the film state. The two synthesized materials had excellent thermal stability, with a high decomposition temperature exceeding 460 °C. The two compounds were used as emitting layers in a non-doped device. The TPA-C-TP device achieved excellent electroluminescence (EL) performance, with Commission Internationale de L′Eclairage co-ordinates of (0.15, 0.07) and an external quantum efficiency of 4.13%, corresponding to an EL peak wavelength of 439 nm. [ABSTRACT FROM AUTHOR]

Advanced multiple resonance induced thermally activated delayed fluorescence (MR‐TADF) emitters have emerged as a privileged motif for applications in organic light‐emitting diodes (OLEDs), because they furnish highly tunable TADF characteristics and high color purity emission. Herein, based on the unique nitrogen‐atom embedding molecular engineering (NEME) strategy, a series of compounds BN‐TP‐Nx (x=1, 2, 3, 4) have been customized. The nitrogen‐atom anchored at different position of triphenylene hexagonal lattice entails varying degrees of perturbation to the electronic structure. The newly‐constructed emitters have demonstrated the precise regulation of emission maxima of MR‐TADF emitters to meet the actual industrial demand, and further enormously enriched the MR‐TADF molecular reservoir. The BN‐TP‐N3‐based OLED exhibits ultrapure green emission, with peak of 524 nm, full‐width at half‐maximum (FWHM) of 33 nm, Commission Internationale de L'Eclairage (CIE) coordinates of (0.23, 0.71), and maximum external quantum efficiency (EQE) of 37.3 %. [ABSTRACT FROM AUTHOR]

Advanced multiple resonance induced thermally activated delayed fluorescence (MR‐TADF) emitters have emerged as a privileged motif for applications in organic light‐emitting diodes (OLEDs), because they furnish highly tunable TADF characteristics and high color purity emission. Herein, based on the unique nitrogen‐atom embedding molecular engineering (NEME) strategy, a series of compounds BN‐TP‐Nx (x=1, 2, 3, 4) have been customized. The nitrogen‐atom anchored at different position of triphenylene hexagonal lattice entails varying degrees of perturbation to the electronic structure. The newly‐constructed emitters have demonstrated the precise regulation of emission maxima of MR‐TADF emitters to meet the actual industrial demand, and further enormously enriched the MR‐TADF molecular reservoir. The BN‐TP‐N3‐based OLED exhibits ultrapure green emission, with peak of 524 nm, full‐width at half‐maximum (FWHM) of 33 nm, Commission Internationale de L'Eclairage (CIE) coordinates of (0.23, 0.71), and maximum external quantum efficiency (EQE) of 37.3 %. [ABSTRACT FROM AUTHOR]

The chemical diversity and structural flexibility of lead halide perovskites (LHPs) offer tremendous opportunities to tune their optical properties through internal molecular engineering and external stimuli. Herein, we report the wide‐range and ultrapure photoluminescence emissions in a family of homologous 2D LHPs, [MeOPEA]2PbBr4−4xI4x (MeOPEA=4‐methoxyphenethylammonium; x=0, 0.2, 0.425, 0.575, 1) enabled through internal chemical pressure and external hydrostatic pressure. The chemical pressure, induced by the C−H⋅⋅⋅π interactions and halogen doping/substitution strengthens the structural rigidity to give sustained narrow emissions, and regulates the emission energy, respectively. Further manipulation of physical pressure leads to wide‐range emission tuning from 412 to 647 nm in a continuous and reversible manner. This work could open up new pathways for developing 2D LHP emitters with ultra‐wide color gamut and high color purity which are highly useful for pressure sensing. [ABSTRACT FROM AUTHOR]

The chemical diversity and structural flexibility of lead halide perovskites (LHPs) offer tremendous opportunities to tune their optical properties through internal molecular engineering and external stimuli. Herein, we report the wide‐range and ultrapure photoluminescence emissions in a family of homologous 2D LHPs, [MeOPEA]2PbBr4−4xI4x (MeOPEA=4‐methoxyphenethylammonium; x=0, 0.2, 0.425, 0.575, 1) enabled through internal chemical pressure and external hydrostatic pressure. The chemical pressure, induced by the C−H⋅⋅⋅π interactions and halogen doping/substitution strengthens the structural rigidity to give sustained narrow emissions, and regulates the emission energy, respectively. Further manipulation of physical pressure leads to wide‐range emission tuning from 412 to 647 nm in a continuous and reversible manner. This work could open up new pathways for developing 2D LHP emitters with ultra‐wide color gamut and high color purity which are highly useful for pressure sensing. [ABSTRACT FROM AUTHOR]

In this study, Eu3+ and K+ co‐doped Ca3WO6 double perovskite, a high‐color‐purity red phosphor, is quantitatively investigated using synchrotron X‐ray diffraction Rietveld refinement, energy dispersive X‐ray spectroscopy, and high‐resolution PL spectroscopy. The Eu3+ fluorescence line‐narrowing (FLN) results, used to estimate the Eu3+ occupation at given sites (so‐called A and B sites) in the host crystal (A2BMO6; A, B = Ca; M = W), reveal that the Eu3+ ions have a twin distribution in both the A and B sites with high asymmetry ratios of ΛA = 9.7 and ΛB = 10.7, respectively. More interestingly, at lower Eu3+ doping levels, the ions are predominantly located at the B sites (≈75%), indicating that the high color purity of Ca3WO6:(Eu3+, K+) is mainly caused by the high asymmetry ratios of the Eu3+ sites. Rietveld refinement combined with the FLN technique provides more reliable results for increasing the Eu3+ substitution at the A site with Eu3+ and K+ doping concentrations, which lower the lattice energy of Ca3WO6:(Eu3+, K+). The structural distortions owing to K+ co‐doping in terms of the quadratic elongation and bond‐angle variance exhibit good correlations with the Ca(Eu)O12 A‐site cuboctahedra and Ca(Eu)O6 B‐site octahedra, partially accounting for the higher Λ values. [ABSTRACT FROM AUTHOR]

Rare-earth doped phosphors have received growing interest in the luminescence field, and hold great potential for lighting and display backlight applications. Nonetheless, the practical implementation of white light-emitting diodes requires the development of a cost-effective and high-performance red phosphor, which is still a significant challenge. In this paper, Eu3+ doped Ba3Na0.32Nb6O12(Si2O7)2 red phosphors were prepared using a high-temperature solid-state method. The structure and phase purity of the samples were analyzed in detail by powder X-ray diffraction (XRD), structure refinement and energy dispersive spectroscopy analysis. Under 395 nm excitation, the phosphor exhibited an intense red emission due to the 5D0 → 7FJ (J = 1, 2, 3, 4) transitions. Through decay curve measurements, it is found that the decay time corresponding to the double-exponential equation decreased with the increase of activator concentration. Theoretical calculations showed that the quadrupole–quadrupole interaction played a dominant role in concentration quenching. The CIE chromaticity coordinates of the phosphor were (0.6436, 0.3556) and the color purity reached 92.07%, indicating that the sample has high color purity. In addition, the temperature-dependent intensity was investigated in detail. The results demonstrated that Ba3Na0.32Nb6O12(Si2O7)2:Eu3+ is a potential red-emitting phosphor for near-ultraviolet based white light-emitting diodes. [ABSTRACT FROM AUTHOR]

• Ultrathin silica shells enhance PNC stability, enabling straightforward introduction in ML platforms. • Achieved superior color purity with a narrow FWHM of 32 nm for advanced ML applications. • Demonstrated high durability of PMP film under extreme conditions. The quest for advanced mechanoluminescence (ML) systems with precise color control and a broad color gamut is pivotal for developing flexible display technologies. Despite significant progress in embedding ML phosphors into elastic polymer matrices to enhance flexibility and resilience, achieving high color purity and a broad color spectrum remains a substantial challenge. This study introduces an innovative approach by incorporating ultrathin silica-encapsulated perovskite nanocrystals (PNCs) into the ML platform, leveraging their exceptional color purity and high photoluminescence quantum yield. Our encapsulation technique, which covers PNCs with SiO 2 shells, not only enhances the environmental stability of PNCs but also enables their integration into a polydimethylsiloxane (PDMS)-based ML matrix, thereby forming a robust perovskite mechanoluminescence platform (PMP) film. This strategy significantly improves ML color purity with a full width at half maximum (FWHM) of 32 nm, as well as leading to high ML stability in various harsh conditions such as heating and water immersion. Our findings demonstrate the potential of silica-encapsulated PNCs to transcend the conventional limitations of ML systems, marking a significant stride towards the realization of advanced flexible displays with superior color purity. [ABSTRACT FROM AUTHOR]

In this paper, a series of K5La1-x(MoO4)4: xSm3+ and K5La0.86(MoO4)4: 0.07Sm3+, 0.07Ln3+ (Ln = Sc, Y or Gd) red phosphors were prepared by calcining the mixed raw powders at 600 °C. Meanwhile, the composition and fluorescence properties of the phosphors, especially for the thermal stability, were analyzed in detail. The results indicate that the K5La1-x(MoO4)4: xSm3+ phosphors can be effectively excited at 401 nm and emit red light with three main peaks at 561 nm, 600 nm and 646 nm, attributed to the 4G5/2→6Hj/2 (j = 5, 7 and 9) energy transitions of the Sm3+ ion respectively, among which the K5La0.93(MoO4)4: 0.07Sm3+ exhibits the highest intensity. The quenching mechanism is ascribed to the dipole-dipole interaction. Ln3+ co-doping does not change the shape and peaking position of the excitation and emission spectra of K5La0.93(MoO4)4: 0.07Sm3+, but further increases the emission intensity in different degrees. Particularly, K5La0.86(MoO4)4: 0.07Sm3+, 0.07Gd3+ demonstrates a high quantum efficiency of 74.63%, a low color temperature (1753 K), and a high color purity of up to 99.97%. It is worth noting that all the phosphors have a good thermal stability, even a zero quenching phenomenon occurs, attributed to the electron traps confirmed by the TL spectrum. [ABSTRACT FROM AUTHOR]

Red phosphors based on BaLaLiTeO6 doped with Eu3+ were prepared by high temperature solid state method. The XRD patterns for the representative samples revealed its single phase structure and the scanning electron microscopes were studied to reveal the morphology and homogeneous distribution of particles with different size. In addition, the density of states and partial density of states of each element revealed that Ba-O and La-O groups are the main factors that determine the optical properties of the BaLaLiTeO6. When emitted by 394 nm near-ultraviolet, all the samples emit bright red light near 618 nm because of 5D0 → 7F2 transition of Eu3+ ions. The optimal doping concentration of Eu3+ in BaLaLiTeO6 is 0.20 and the mechanism of concentration quenching is the dipole-quadrupole interaction. Besides, the temperature-dependent emission spectra of BaLaLiTeO6:0.2Eu3+ red sample were studied systematically and the thermal activation energy of the sample was 0.30 eV, indicating its good thermal stability. The lifetime of Eu3+ ions is in the millisecond level and the CIE chromaticity coordinate of BaLaLiTeO6:0.2Eu3+ is (0.6436, 0.3535) with a high color purity of 99.4%, which is close to the standard of red chromaticity. To sum up, the BaLaLiTeO6:Eu3+ phosphors are the hopeful red component applied in the white light illumination. [ABSTRACT FROM AUTHOR]

Materials with tunable emission colors has attracted increasing interest in both fundamental research and applications. As a key member of light‐emitting materials family, lanthanide doped upconversion nanoparticles (UCNPs) have been intensively demonstrated to emit light in any color upon near‐infrared excitation. However, realizing the trichromatic emission in UCNPs with a fixed composition remains a great challenge. Here, without excitation pulsed modulation and three different near‐infrared pumping, we report an experimental design to fine‐control emission in the full color gamut from core–shell‐structured UCNPs by manipulating the energy migration through dual‐channel pump scheme. We also demonstrate their potential application in full‐color display. These findings may benefit the future development of convenient and versatile optical methos for multicolor tuning and open up the possibility of constructing full‐color volumetric display systems with high spatiotemporal resolution. [ABSTRACT FROM AUTHOR]

Materials with tunable emission colors has attracted increasing interest in both fundamental research and applications. As a key member of light‐emitting materials family, lanthanide doped upconversion nanoparticles (UCNPs) have been intensively demonstrated to emit light in any color upon near‐infrared excitation. However, realizing the trichromatic emission in UCNPs with a fixed composition remains a great challenge. Here, without excitation pulsed modulation and three different near‐infrared pumping, we report an experimental design to fine‐control emission in the full color gamut from core–shell‐structured UCNPs by manipulating the energy migration through dual‐channel pump scheme. We also demonstrate their potential application in full‐color display. These findings may benefit the future development of convenient and versatile optical methos for multicolor tuning and open up the possibility of constructing full‐color volumetric display systems with high spatiotemporal resolution. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) are renowned for their unique properties with numerous and growing applications in various fields and industries. Although several methods are available to prepare CDs, low conversion yield, tedious purification processes and poor color purity remain major drawbacks. To address these issues, a cooling stage for full protonation prior to direct heating has been developed. This innovative method produces high-color purity solid-state CDs with a conversion yield of up to 99.5% in less than 6 min. The CDs synthesized by this method exhibited a highly crystalline structure, as confirmed by HRTEM, Raman and XRD analyses. In addition, the emission profile of the CDs could be effectively tuned by reducing the amount of concentrated sulfuric acid, resulting in a shift of the emission from 484 to 650 nm. The high-color purity of the CDs is postulated to be due to the solvent cage effect. Overall, this study presents a simple, efficient and rapid method for the preparation of high-quality CDs with excellent color purity and crystallinity. [ABSTRACT FROM AUTHOR]

Red phosphor plays a key role in improving the lighting and display quality of phosphor-converted white light-emitting diodes (pc-WLEDs). Meanwhile, developing new luminescent matrix materials can positively contribute to the acquisition of ideal and efficient phosphors. In this work, we propose a novel red-emitting Na 5 W 3 O 9 F 5 :Eu3+ (NWOF:Eu3+) phosphor. The phase composition, morphology, electronic structure and photoluminescence properties of the NWOF:Eu3+ phosphor were systematically investigated. The EXAFS results prove that the Eu3+ dopants occupy the Na2 and Na3 sites in the NWOF host. Under 466 nm blue light excitation, NWOF: x Eu3+ (0.05 ≤ x ≤ 0.25) phosphors display a dominant red emission at 607 nm and achieves a high color purity (97.44%) due to the dominant electric dipole transition (5D 0 →7F 2) of Eu3+ ions. Impressively, this red-emitting NWOF:0.25Eu3+ phosphor exhibits relatively superior thermal stability (450 K, >50%) and excellent chromaticity stability (2.32 × 10−4 ≤ ΔE ≤ 6.23 × 10−3) from 298 K to 498 K. The activation energy for thermal quenching effect is determined to be 0.22 eV. Moreover, the pc-WLED was fabricated by coupling a 460 nm blue chip with the as-synthesized NWOF:0.25Eu3+ red phosphor and commercial YAG:Ce3+ phosphor. The optical parameters of the as-fabricated pc-WLED are also measured, and the CIE coordinates remain almost constant as the drive current increases from 20 mA to 120 mA. These results indicate that the NWOF:0.25Eu3+ red phosphors should be a suitable candidate as a red component for the preparation of pc-WLEDs. [Display omitted] [ABSTRACT FROM AUTHOR]

Multi‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters have been studied to address the issue of the broadband emission in organic light‐emitting diodes (OLEDs). Herein, the authors have systematically investigated the effect of electron‐donating or ‐withdrawing units in the para position of B atom on the optoelectronic emission modulation BCz‐BN MR‐TADF emitters. Due to the enhanced spin‐orbit coupling (SOC) effect, BN(p)SCH3 with electron structure of para‐D‐π‐B is synthesized by introducing a heavy S atom into the para position of B atom of BCz‐BN. By oxidizing BN(p)SCH3, BN(p)SOCH3 and BN(p)SO2CH3 with electron structure of para‐A‐π‐B have been synthesized. The quantum simulations and photophysical studies have illustrated BN(p)SCH3 can exhibit large reverse intersystem crossing rate constant (kRISC) of 6.4 × 104 s−1 due to the large SOC constants and small singlet‐triplet energy splitting (ΔEST) of 0.12 eV. BN(p)SOCH3 and BN(p)SO2CH3 with electron structure of para‐A‐π‐B displayed red‐shift emissions with smaller full‐width at half‐maximum (FWHM) values of ≈21 nm and kRISC values owing to enhanced ΔEST and the low emission contribution of the triplet excitons in contrast to those of BN(p)SCH3 with electron structure of para‐D‐π‐B. Consequently, BN(p)SCH3‐based OLEDs show highly efficient blue emission with an external quantum efficiency (EQE) of 26.2% and excellent color purity. [ABSTRACT FROM AUTHOR]

The development of efficient ultraviolet (UV) organic light-emitting materials and devices holds paramount significance for their practical applications. Nonetheless, attaining a short-wavelength electroluminescence peak of less than 390 nm while maintaining high color purity in non-doped devices remains a formidable challenge. In this work, we have successfully designed and synthesized two UV hybridized local and charge transfer fluorophores, specifically 4DBF-CZCN and 2DBF-CZCN, which are comprised of cyanide-modified phenylcarbazole and a weak electron donor dibenzofuran. And the properties of excited state are well regulated through the different linking site of dibenzofuran. The resulting non-doped devices exhibit not only emission peak wavelengths of 390 and 388 nm, accompanied by narrow full-width-at-half-maximums of 42 and 38 nm, respectively, corresponding to color coordinates of (0.164, 0.034) and (0.164, 0.036), but also admirable external quantum efficiencies of 3.00 % and 2.86 % at high luminance levels of 1910 and 1252 cd m−2, respectively. Two ultraviolet fluorophores with hybridized local and charge transfer state were developed by incorporating N -(4-cyanophenyl)carbazole framework with ancillary donor dibenzofuran. [Display omitted] • Two ultraviolet fluorophores with HLCT excited state were designed and synthesized. • The non-doped devices emit stable ultraviolet light with peaks of 390 and 388 nm. • Maximum EQE of ∼3.0 % was achieved at a high luminance of 1910 cd m−2. [ABSTRACT FROM AUTHOR]

Multiple resonance (MR) type thermally activated delayed fluorescence (TADF) emitters are very promising in the high‐resolution and high‐efficiency displays, due to their narrow and highly efficient optical emissions. Early MR‐TADF cores that show only short‐range charge‐transfer (CT) electronic excitations hardly afford ideal performances (e.g., show low efficiencies) in organic light‐emitting diodes (OLEDs). This work thus designs and synthesizes two MR‐TADF emitters (TCzBN‐BP and TCzBN‐FP), where the same MR core TCzBN is chemically modified by the acceptor fragments benzophenone/9‐fluorenone (BP/FP) to incorporate long‐range CT excitations in the two molecules. OLEDs exploiting TCzBN‐BP as emitter, in which short‐range CT excitation is dominant in the first singlet (S1) excited state, achieve a maximum external quantum efficiency (EQE) of 35.6% and a narrow emission bandwidth of 35 nm. In contrast, OLEDs exploiting TCzBN‐FP with an overloaded long‐range CT excitation in the S1 state exhibit a maximum EQE of 27.2% and a broadened emission bandwidth of 56 nm. This work not only shows the importance of careful management of long‐ and short‐range CT excitations, but also provides a new insight into the structure–property relationship in the MR‐TADF emitters, which thus promotes the design of more novel MR‐TADF emitters with high efficiencies and high color purity. [ABSTRACT FROM AUTHOR]

Gel-combustion method was implemented in current research to generate Strontium Lanthanum Aluminate (LaSr 2 AlO 5) phosphors doped with Sm3+ ions and have a potential to emit orangish-red light. In order to analyze phase characteristics, XRD technique was employed. XRD patterns of synthesized materials were closely resembles the JCPDS pattern indicated on card no. 70–2197, which define the tetragonal symmetry of the material with I 4/ mcm space group. The morphological, optical band energies and elemental analyses were done via TEM, DRS and EDX investigation respectively. The Sm3+ activated LaSr 2 AlO 5 phosphor's PL spectra monitored at 406 nm excitation indicate intense visible orangish-red emission at 602 nm owing to the 4G 5/2 → 6H 7/2 transition. Concentration quenching was obtained at 4 mol % content of Sm3+ owed to the dipole-dipole interaction among activated ions. The calculated lifetimes have been observed to shorten as content of Sm3+ ions in the phosphors rises. The CIE (0.6069, 0.3905) value, CCT (1382 K) value, 99.4 % color purity of the optimum sample was calculated which placed in orange-red space. The fabricated phosphor has excellent thermal durability up to 498 K and 0.1686 eV activation energy. Finally, the results of all the research allow us to consider that Sm3+ doped LaSr 2 AlO 5 phosphor is appropriate for warm LEDs. [Display omitted] • Gel-combustion method was employed to synthesized warm reddish-orange light emissive LaSr 2 AlO 5 :Sm3+ nanophosphors. • LaSr 2 AlO 5 :Sm3+ crystallized into tetragonal crystal structure with symmetry group of I 4/ mcm. • Upon 406 nm excitation, PL spectra indicate intense reddish-orange emission at 602 nm owing to 4G 5/2. → 6H 7/2 transition. Concentration quenching was obtained at 4 mol % content of Sm3+ owed to the dipole-dipole interaction. • The fabricated phosphor has excellent thermal durability up to 498 K and 0.1686 eV activation energy. [ABSTRACT FROM AUTHOR]

• MgTi 2 O 5 : xEu3+ phosphors are synthesized by solid-state reaction method. • Under 465 nm excitation, intense red emission was obtained at 615 nm. • Internal quantum efficiency of the phosphor was determined to be 31.65 %. • Phosphors have high color purity and warm light emission. • Synthesized red phosphor is a suitable candidate for pc-wLEDs. As one of the critical components for achieving high-quality white light emitting diodes (w-LEDs) are efficient phosphors, a series of intense red emitting Eu3+doped magnesium dititanate (Mg (1- x) Ti 2 O 5 : x Eu3+; x = 0, 0.005, 0.008, 0.01, 0.02 and 0.03 mol) phosphors were prepared via solid-state reaction method. The X-ray diffraction (XRD) patterns confirmed the phase purity and orthorhombic structure of the prepared phosphors. The Ti-O functional groups were detected from the Fourier transform infrared (FTIR) spectra and Field emission scanning electron microscopy (FESEM) images revealed agglomerated spherical-like shaped phosphor particles. Under 465 nm excitation, intense red emission corresponding to 5D 0 →7F J (J = 0, 1, 2, 3, and 4) transitions of Eu3+ ions were recorded in the photoluminescence (PL) spectra with an intense peak at 615 nm. The optimum concentration of Eu3+ ions was determined to be 1 mol% and the concentration quenching mechanism was due to the interaction between adjacent Eu3+ ions. The lifetime values of the samples were in the millisecond range and the internal quantum efficiency was determined to be 31.65 %. The Commission Internationale de l'Eclairage (CIE) coordinates of the optimum sample Mg 0.99 Ti 2 O 5 :0.01Eu3+ are (0.6421, 0.3575), lies in the red region with 99.9 % color purity and have warm correlated color temperature (CCT) values. Therefore obtained results suggest that the prepared Mg (1- x) Ti 2 O 5 : x Eu3+phosphors can be used as an efficient red phosphor for w-LED applications. [Display omitted] [ABSTRACT FROM AUTHOR]

The novel orange-red emitting K 5 Y(MoO 4) 4 : x Sm3+ (KYMO: x Sm3+) (1 mol% ≤ x ≤ 35 mol%) phosphors were synthesized through solid-phase reaction. The KYMO:Sm3+ phosphors were mainly analyzed for purity phase, luminescence properties, and thermostability. Under 403 nm excitation, KYMO:10 mol%Sm3+ possesses four distinct emission peaks. The dominant emission peak is situated at 645 nm, corresponding to the 4G 5/2 → 6H 7/2 electron transitions. With x = 10 mol%, the KYMO: x Sm3+ phosphor has the optimal doping concentration. The color purity reaches as high as 99.9 %. KYMO:10 mol%Sm3+ presents good thermostability with T 0.5 > 480 K and resistance to color drift (Δ E = 0.012 at 420 K). The lifetime for KYMO:10 mol%Sm3+ is 1.16 ms. The internal quantum efficiency (IQE) reaches 62.74 %. At 480 K, the maximum temperature sensing sensitivities of the FIR of I 564 /I 599 are 5.19 × 10−4 (S a) and 18 % (S r). The assembled WLED displays an excellent color rendering index (CRI, R a) of 94, Commission International de L′ Eclairage (CIE) coordinates (0.333, 0.346), and a correlated color temperature (CCT) of 5464 K. In summary, KYMO:Sm3+ phosphors possess great promise for high CRI white-light-emitting diodes (WLEDs) and potential feasibility for temperature sensing. • K 5 Y(MoO 4) 4 :Sm3+ phosphors have been synthesized via solid-state reaction firstly. • The phosphor emits bright orange-red light excited by 403 nm. • The synthesized phosphors exhibit the superior color purity (99.8 %–99.9 %). • The fabricated WLED exhibits a high color rendering index (R a = 94). [ABSTRACT FROM AUTHOR]

In this study, a Sm3+ ion-doped double perovskite structure oxide was developed to obtain a novel Ca 2 GaNbO 6 : Sm3+ orange-red phosphor, which has compensated for the lack of a red component in commercial wLEDs. The results of morphological features and phase structure have confirmed that the synthesized compound maintains the same structure as Ca 2 GaNbO 6, and that Sm3+ successfully enters into the main lattice of Ca 2 GaNbO 6. In terms of optical properties, the photoluminescence (PL) emission spectra monitored at 406 nm has the strongest emission peak at 599 nm and shows strong orange-red light. The spectral shapes of PL at different concentrations remain consistent without wavelength drift, and perform best when the concentration is 3 mol%, that is, the concentration quenching point is 3 mol%. The quenching phenomenon is believed to be mainly attributed to dipole-dipole (d-d) interaction. The Ca 2 GaNbO 6 : 0.03Sm3+ phosphor shows excellent color purity (CP = 99.0 %) and low color temperature (CCT = 1664 K) in terms of chromaticity (CIE). In terms of heat resistance, the thermal stability of Ca 2 GaNbO 6 : 0.03Sm3+ phosphor is 82.80 % (423 K). The internal quantum efficiency (IQE) is 34.4 %. In terms of applications, the wLEDs made of Ca 2 GaNbO 6 : 0.03Sm3+ phosphor emits warm white light and exhibit excellent performance in color rendering index and correlated color temperature (CRI = 94.5, CCT = 3877 K). At the same time, Ca 2 GaNbO 6 : Sm3+ phosphor shows good solubility in PVA. Research shows that Ca 2 GaNbO 6 : Sm3+ phosphor has good performance in the fields of wLEDs and security ink. • Ca 2 GaNbO 6 : Sm3+ double perovskite structure phosphor was firstly synthesized via a high-temperature solid-state method. • Ca 2 GaNbO 6 : 0.03Sm3+ has excellent color purity (CP = 99.0 %) and good thermal stability (82.80 % @ 423 K). • The WLED prepared using the phosphor emits warm white light with excellent color rendering index and correlated color temperature Ra = 94.5, CCT = 3877 K). • The prepared ink was applied to black paper, plastic, and metal alloy materials to verify the practicality of Ca 2 GaNbO 6 : 0.03Sm3+ in the field of anti-counterfeiting security ink. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sr 3 MgNb 2 O 9 :Eu3+ phosphors have been firstly synthesized via high temperature solid-phase method. • The synthesized phosphors exhibit a high color purity (99.9%). • The fabricated w-LED has an appropriate CCT (4685 K) and high R a (88). • Sr 3 MgNb 2 O 9 :Eu3+ phosphors have potential to be used for LFP detection fields. A series of novel phosphors, doping Eu3+ and Na+ ions in the Sr 3 MgNb 2 O 9 (SMNO) crystal lattice (SMNO: x Eu3+, x Na+, x = 0.5–30 mol%), was successfully synthesized through high-temperature solid-state reaction. X-ray diffraction (XRD) analysis and Rietveld refinement confirmed the successful synthesis of SMNO:Eu3+, Na+. The phosphor belongs to the hexagonal crystal system and the P 3 ¯ m 1 (No.164) space group. The bandgap energy of SMNO was calculated with Materials Studio and measured with the use of diffuse reflectance spectroscopy. The excitation spectrum of SMNO:Eu3+, Na+ displays multiple narrow absorption peaks in the violet-blue region as well as a charge transfer band (CTB) near 300 nm, exhibiting the highest peak at 394 nm. Four distinct characteristic peaks are observed in the emission spectrum of SMNO:Eu3+, Na+. Notably, the peak at 601 nm shows the highest emission intensity due to the radiative transition from 5D 0 →7F 2. By varying doping concentrations, it was determined that an optimal concentration of 5 mol%Eu3+ resulted in phosphors, with high color purity exceeding 99 %. Concentration quenching is attributed to the nearest neighbor ions interaction. Furthermore, SMNO:Eu3+, Na+ exhibited good stability in 300–480 K, with luminescent intensity remaining 68.6 % at 420 K and 54.4 % at 480 K compared to room temperature (300 K). The internal quantum efficiency (IQE) of SMNO:5%Eu3+, 5 %Na+ is 65.0 %. Both red and white light-emitting diodes (LEDs) were prepared using SMNO:Eu3+, Na+. The chromaticity coordinates of w-LED were measured as (0.357, 0.376), correlating to a correlated color temperature (CCT) of 4685 K and exhibiting a good color rendering index (CRI, R a = 88). Additionally, the latent fingerprint (LFP) development demonstrated clear visualization of Levels I-III characteristic structures of fingerprints when utilizing SMNO:Eu3+, Na+. These findings suggest promising applications for SMNO:Eu3+, Na+ in w-LED lighting and LFP development. [ABSTRACT FROM AUTHOR]

• A novel red emitting NaLa (1-x) MgTeO 6 :xSm3+ phosphors were synthesized. • Under n-UV excitation, the synthesized phosphors exhibit warm red emission with high color purity. • The emission range of synthesized phosphor is sensitive to human eye. • The phosphor incorporated security ink shows bright luminescence under n-UV light and invisible under day light. • The phosphor found applications in WLEDs and security ink applications. Recently, red phosphors are extensively developed to find applications in phosphor converted white LEDs (pc-WLEDs) and anti-counterfeiting. In this work, samarium doped sodium lanthanum magnesium tellurate (NaLaMgTeO 6 :Sm3+) red emitting phosphors have been synthesized for the first time via solid state reaction method. Rietveld refinement of XRD pattern reveals monoclinic crystal structure of NaLaMgTeO 6. Under 404 nm (6H 5/2 → 4F 7/2) n-UV excitation, NLMT:Sm3+ phosphor shows red emission at 643 nm (4 5/2 → 6 9/2) with color purity 100 % and the obtained CCT value corresponds to warm light source. Temperature-dependent PL analysis of NLMT:Sm3+ exhibits good thermal stability. The anti-counterfeiting security ink was developed using optimized phosphor and the information was encrypted on different surfaces using the prepared security ink. The encrypted data was decoded only by n-UV light. The aforementioned results revealed that NLMT:Sm3+ is a highly effective phosphor as a red component for pc-WLEDs and luminescent dye for anti-counterfeiting applications. [Display omitted] [ABSTRACT FROM AUTHOR]

• This study discloses the first time synthesis of Sm3+ ion doped CaAl 4 O 7 phosphor by microwave-assisted combustion technique. • Fabrication of CaAl 4 O 7 : Sm3+ phosphor based P-i-G structure. • Orange emission observed at 601 nm manifest that the phosphor can be utilized as an orange-emitting phosphor in lighting applications. • Excellent color purity of 99.21% and CRI of 77 were obtained for prepared phosphor. • Fabricated P-i-G possesses luminous efficacy and luminous efficiency of 360 lm/W and 52.70 % respectively. This work reports the synthesis of Sm3+ ion doped calcium dialuminate phosphor by microwave-assisted combustion synthesis technique. Phase purity and the crystal structure of the phosphors were affirmed by PXRD analysis and was found to have monoclinic structure. SEM study was performed to analyze the surface morphology. FTIR study clarifies the existence of functional groups. The optical bandgap of 4.43 eV was determined for CaAl 4 O 7 :Sm3+ (x = 0.03) sample. The emission spectra of the sample recorded upon excitation at 403 nm suggest orange color emission around 601 nm pertaining to the transition 4 G 5 / 2 →6 H 7 / 2 of Sm3+ ions. The optimal dopant concentration was established at 3 mol%. CIE chromaticity coordinates of (x = 0.6029, y = 0.3964) were established for the optimized sample. Correlated color temperature of 1620 K demonstrates the emission of light in warmer region. The superior color purity of 99.21 % and color rendering index of 77 for the optimized phosphor material was manifested. The photoluminescence (PL) decay time (for Sm3+ concentration = 0.03 mol) was found to be 0.73 ms. Thermal stability of the sample was investigated and the activation energy was determined to be 0.152 eV by temperature-dependent PL study. To explore the lighting ability of the phosphor, phosphor-in-glass (P-i-G) material was fabricated. CaAl 4 O 7 :Sm3+ (x = 0.03) based P-i-G material validates excellent luminous efficacy (360 lm/W) and luminous efficiency (52.70 %) which affirms its practical applications. [ABSTRACT FROM AUTHOR]

Thermally activated delayed fluorescence (TADF) emitters induced by the multiple resonance (MR) effect have garnered considerable attention. However, it is difficult to develop MR‐TADF emitters that maintain high color purities in the red region. In this work, the importance of excited state alignments of MR‐based donor‐acceptor (D‐A) molecules in determining their preferring characteristics is clarified. By using the newly designed molecule mBDPA‐TOAT whose apparent excited states show hybridization of MR and intersegmental charge‐transfer features as an emitter in an organic light‐emitting diode (OLED), a high external quantum efficiency of 17.3% is achieved with a full width at half‐maximum of 45 nm (154 meV) and Commission Internationale de L'Éclairage coordinate of (0.61, 0.39). This work demonstrates when introducing D‐A typed structures, features, and alignments of molecular excited states determine ultimate material properties. This could help to develop high efficiency and high color purity TADF emitters toward long wavelength range. [ABSTRACT FROM AUTHOR]

To enhance the display quality of light‐emitting diodes (LEDs), it is of great significance to exploit green/yellow‐emitting phosphors with narrow emission band, high quantum yield, and excellent color purity to satisfy the application. Herein, orthophosphate‐based green/yellow‐emitting Na3Tb(PO4)2:Ce3+/Eu2+ (NTPO:Ce3+/Eu2+) phosphors have been successfully synthesized by a facile solid‐state reaction method. The absorption band of NTPO samples was extended to the near‐ultraviolet region and the absorption efficiency was significantly improved owing to a highly efficient energy transfer from Ce3+/Eu2+ ion to Tb3+ ion in NTPO host certified by time‐resolved PL spectra. Upon 300 nm excitation, the NTPO:Ce3+ is characterized by ultra‐narrow‐band green emission of Tb3+ with an absolute quantum yield of 94.5%. Unexpectedly, NTPO:Eu2+ emits bright yellow light with a color purity of 73% as a result of the blending of green light emission from Tb3+ and red light emission from Eu3+. The thermal stability has been improved by controlling the stoichiometric ratio of Na+. The prototype white LED used yellow‐emitting NTPO:Eu2+ phosphor has higher color‐rendering index (Ra = 83.5), lower correlated color temperature (CCT = 5206 K), and closer CIE color coordinates (0.338, 0.3187) to the standard white point at (0.333, 0.333) than that used green‐emitting NTPO:Ce3+ phosphor, indicating the addition of the yellow light component improved the Ra of the trichromatic (RGB) materials. [ABSTRACT FROM AUTHOR]

Purely organic compounds with thermally activated delayed fluorescence (TADF) are promising sustainable emitters for organic light‐emitting diodes. But the simultaneous realization of a high efficiency, short lifetime, and good color purity in single TADF molecule remains challenging. Herein it is reported that the confinement of rigid and planar N‐ and B‐centered donor and acceptor in sandwich‐type structures, named BNB‐m and BNB‐p, can lead to green TADF emissions with up to unity efficiency and improved color purity from through‐space charge‐transfer excited states. The full width at half maximum of 58 nm (0.28 eV) for BNB‐m is significantly smaller than those for most of the TADF emitters having a twisted donor‐acceptor structure. Single‐crystal structures, NMR spectroscopy, and theoretical simulations manifest the presence of strong noncovalent π‐stacking interactions in BNB‐m which account for the reduced intramolecular motions and enhanced through‐space electronic coupling. With a relatively short delayed fluorescence lifetime of 11 µs, the emitter BNB‐m demonstrates attractive green electroluminescence with a maximum external quantum efficiency (EQE) of 34.9% and an EQE of 27.4% at 1000 cd m−2. This work validates a promising molecular design to TADF emitters which can realize a balanced emission property in terms of color purity and emission lifetime. [ABSTRACT FROM AUTHOR]

Through the incorporation of one electron-rich N^OH-ancillary HL , its [Ir(C^N) 2 (N^O)]- bis -heteroleptic Ir(III)-complex [ Ir(dpbq) 2 (L)] is found to enable color-purity NIR-phosphorescence (λ PL = 780 nm). Moreover, owing to the augmented 3MLCT effect and large transition dipole moment (TDM), the color-purity NIR-emissive efficiency (Φ PL = 3.9%) of [ Ir(dpbq) 2 (L)] is higher than those of the [Ir(dpbq) 2 (O^O)]-analogue. [Display omitted] • C 1 -symmetric [Ir(C^N) 2 (N^O)]- bis -heteroleptic Ir(III)-complex. • Color-purity and near-infrared emission. • 3MLCT and transition dipole moment. In sharp contrast to the success of Ir(III)-complex-based visible-phosphors, the molecular design of their efficient NIR-emissive counter-parts, as constrained by the so-called "energy gap law", is distinctively difficult. Especially, it remains a great challenge to develop new Ir(III)-complex-based phosphors with both efficient and color-purity NIR-emission. Herein, based on the molecular design of [Ir(dpbq) 2 (L)] , the highly conjugated HC^N-main ligand Hdpbq renders the desirable color-purity NIR-phosphorescence (λ PL = 780 nm), and the electron-rich while N^OH-ancillary HL is beneficial to augmented 3MLCT effect and large transition dipole moment (TDM). Accordingly, its color-purity NIR-phosphorescent efficiency (Φ PL = 3.9 %) is significantly higher than those (Φ PL = 1.9–2.5 %) of the [Ir(dpbq) 2 (O^O)]-analogue. [ABSTRACT FROM AUTHOR]

Ho3+-doped BaGd 2 O 4 phosphors sensitized by Yb3+ or Nd3+/Yb3+ have been prepared by solid-state reaction method. Almost pure green UC emission was obtained under 808 nm and 980 nm excitations. The green color purity of BaGd 2 O 4 : Yb3+/Ho3+/Nd3+ phosphor exceeds 93 % in the temperature range of 303 K–483 K under the excitation of 808 nm, indicating an excellent color purity and color stability. [Display omitted] • Strong green emission was obtained in BaGd 2 O 4 : Nd3+/Yb3+/Ho3+ phosphors excited at 808 nm and 980 nm. • The green up-conversion luminescence process of Ho3+ was insensitive to the doping concentration and sample temperature. • The temperature sensitivity of Ho3+ keeps constant in a wide temperature range. • BaGd 2 O 4 : Nd3+/Yb3+/Ho3+ phosphors exhibit high green color purity at different temperatures. Ho3+-doped BaGd 2 O 4 phosphors sensitized by Yb3+ or Nd3+/Yb3+ have been prepared by solid-state reaction method. The effects of concentration and temperature on the up-conversion (UC) luminescence properties and the temperature sensing behavior of the samples were investigated. Intense green UC emission at around 550 nm and weak red UC emission at around 675 nm were obtained under both 808 nm and 980 nm excitations. The relationship between the UC luminescence spectra measured at different temperatures and excitation power densities was analyzed. The results confirmed that the green UC emissions of Ho3+ are two-photon processes, which is insensitive to the sample temperature and excitation wavelength, while the red UC emission under 980 nm excitation is affected by temperature. In addition, the Judd-Ofelt intensity parameters of Ho3+-doped BaGd 2 O 4 phosphors were calculated by using the diffuse reflection spectra and fluorescence lifetime of Ho3+. By inspecting the temperature-varied fluorescence intensity ratio, the temperature sensing property of Nd3+/Yb3+/Ho3+ co-doped BaGd 2 O 4 phosphor under the excitation of 980 nm was investigated and a constant sensitivity was obtained to be 3.2 × 10−4 K−1 within the temperature range of 303–483 K. The green color purity of BaGd 2 O 4 : Yb3+/Ho3+/Nd3+ phosphor exceeds 93 % in the temperature range of 303 K–483 K under the excitation of 808 nm, indicating an excellent color purity and color stability. The results indicate that Ho3+-doped BaGd 2 O 4 phosphors sensitized by Yb3+ or Nd3+/Yb3+ have potential application in temperature sensors and luminescence imaging in complex environments. [ABSTRACT FROM AUTHOR]

Despite concrete efforts to Ir(III)-complex-based NIR-OLEDs/PLEDs, most of them previously reported are not of color-purity NIR-emission, due to the considerable visible-light remnants in the NIR-emissive protocols. Meanwhile, for the limited Ir(III)-complex-based color-purity NIR-OLEDs/PLEDs, it remains a great challenge to realize their high-performance, besides the tackling of non-all-solution-processed operation cost. In this paper, based on the molecular design of [Ir (dpbq) 2 (Ln)] (1 – 2 , n = 1–2), the highly conjugated HC^N-main ligand Hdpbq renders its Ir(III)-complexes' desirable color-purity NIR-phosphorescence (λ PL = 780 nm), while electrochemical properties and excited-state dynamics are deeply dependent on the varied N^OH-ancillary ligands with different electronic effects. Especially for the [Ir (dpbq) 2 (L2)] (2), its color-purity NIR-phosphorescent high-efficiency (Φ PL = 3.6 %) is arisen from augmented 3MLCT effect and large transition dipole moment (TDM). Importantly, upon its all-solution-processing device fabrication, the first-example of all-solution-processed and color-purity NIR-PLED (λ EL = 780 nm; η EQE Max = 1.4 %), the best of our knowledge, was realized. Using [Ir (dpbq) 2 (Ln)] (1 – 2 , n = 1–2) characteristic of color-purity NIR-phosphorescence (λ em = 780 nm) as dopants, the first-examples of all-solution-processed and color-purity NIR-PLEDs were realized. Especially for the [Ir (dpbq) 2 (L2)] (2), its high-efficiency (Φ PL = 3.6 % and η EQE Max = 1.4 %) is arisen from augmented 3MLCT effect and large transition dipole moment (TDM). [Display omitted] • C 1 -symmetric [Ir(C^N) 2 (N^O)]- bis -heteroleptic Ir(III)-complexes. • Color-purity near-infrared emission. • All-solution-processed polymer light-emitting diodes (PLEDs). [ABSTRACT FROM AUTHOR]

Luminescent materials have garnered interest as alternative dusting powders for the enhanced visualization of latent fingerprints (LFPs) due to their pronounced emission, vivid fluorescence, and high contrast capabilities. This study introduces, for the first time, a novel red garnet phosphor doped with Eu3+ in the Ca 3 Zr 2 SiGa 2 O 12 (CZSG) matrix. By substituting Eu3+ ions for Ca2+ ions, the hypersensitive transition of the Eu3+ ions is modulated, leading the phosphor to exhibit an outstanding color purity, nearing 100 %. The optimal emission intensity of the phosphor is achieved with a Eu3+ concentration of 12 %. Notably, it showcases high thermal stability, retaining 96.5 % of its intensity at 423 K, and has a high activation energy of 0.4385 eV. This phosphor has displayed its potential in latent fingerprint analysis, as evidenced by its effective application in visualizing latent fingerprints. • A red phosphor with high color purity (near 100 %) and thermal stability (96.5 % @ 423 K) was obtained. • A strategy takes into account both hypersensitive transition of Eu3+ and host lattices with higher rigidity. • The novel material serves as an effective labeling marker for the complete visualization of latent fingerprints. [ABSTRACT FROM AUTHOR]

Spherical silicate phosphor has widespread application in display or lighting industry. By using spherical silica particles as the core, we successfully prepared shell-thickness-controllable core/shell spherical particles, which can then be controllably converted to spherical X 1 -Y 2 SiO 5 :Eu (YSO:Eu) and α-Y 2 Si 2 O 7 :Eu (YPS:Eu) particles upon annealing. Even after 1000–1200 °C annealing, both X 1 -YSO:Eu and α-YPS:Eu particles still had the spherical shape and narrow size distribution. The shell thickness and annealing temperature synergistically controlled the phase evolution upon annealing. Thinner shell of around 30 nm, having extremely high chemical reaction activity, promoted the formation of spherical X 1 -YSO:Eu particles at 1000 °C and α-YPS:Eu particles at 1100 °C. Shell of around 85 nm produced spherical X 1 -YSO:Eu particles at 1100 °C and α-YPS:Eu particles at 1200 °C. Thicker shell also promoted the formation of spherical particles, but these particles usually had the mixed silicate phases. The phase-dependent photoluminescence properties were investigated in detail. Both spherical X 1 -YSO:Eu and α-YPS:Eu phosphors emitted reddish-orange color, with nearly 100% color purity and dominant wavelength of around 601 nm, which would absorb great attention for the application in display or lighting devices. Spherical red-emitting X 1 -Y 2 SiO 5 :Eu and α-Y 2 Si 2 O 7 :Eu phosphors having the nearly 100% color purity were obtained, and the phase transformation sequence was clearly clarified. [Display omitted] [ABSTRACT FROM AUTHOR]

Novel cubic perovskite based orange red emissive Sr 9(1-x) Al 6 O 18 : 9 x Sm3+ (0.001 ≤ x ≥ 0.04) nanocrystals were developed by environmentally benign and low temperature urea combustion method. Phase structure analysis showed the cubic structure with Pa 3 ‾ (205) space group. Scanning and transmission electron micrographs reported the agglomerated cubic morphology of the nanoparticles ranging from 40 to 60 nm. EDS (energy dispersive X-ray analysis) outcomes traced the adequate elemental composition of the spectral materials. The prepared nanomaterials displayed the fine orange red emission via 4G 5/2 → 6H 7/2 typical transition centered at 599 nm. Optical analysis asserted the wide band gap values of Sr 8.82 Sm 0.18 Al 6 O 18 (3.77 eV) and Sr 9 Al 6 O 18 (4.08 eV). Reliance of the emission intensity of developed nanophosphors on Sm3+ concentration claimed the Sr 8.82 Sm 0.18 Al 6 O 18 as most desirable one with CIE coordinates (0.5833, 0.4159), 1747 K correlated color temperature (CCT) and color purity of 90.65%. These excellent results proved the relevancy of present nanophosphors as a novel promising material in the development of down conversion white LEDs. Also, the present research findings thus, can be well recurred to explore more about Sr 9 Al 6 O 18 based spectral nanomaterials. [ABSTRACT FROM AUTHOR]