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We investigated the influence of cobalt (II) oxide additive in the amount of 1-3 mol.% on the structure and optical-color characteristics of chromium-containing glass with the following composition (mol.%): 29.6 Na2O; 19.7 B2O3; 49.3 SiO2; and 1.5 Cr2O3. The dependence of the optical-color characteristics of the glasses under study on the thermal treatment of the glass melt at a temperature of 10500C for 20 minutes was established. The thermal treatment resulted in the volumetric crystallization with the subsequent development of the aventurine effect. According to X-ray phase analysis data, the decorative effect was caused by Cr2O3 crystals. By using IR spectroscopy and differential thermal analysis, the structure of the experimental glasses was studied, and the influence of thermal treatment of glass melts on the formation of the structure of glass-ceramic material was established. Aventurine glass of dark blue-green color was obtained with a color tone λ=490 nm, color purity P=11.35%, and lightness L=5.454 %. The nature of the influence of cobalt (II) oxide on the optical-color characteristics of chromium-containing aventurine glass based on the Na2O-B2O3-SiO2 system is of interest for further development of new compositions of decorative ceramic glazes and enamel coatings. [ABSTRACT FROM AUTHOR]

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]

In blue organic light‐emitting diodes (OLEDs), the importance of terminal emitters, which determine device operational characteristics, has been grown. Although multiple resonance (MR) type emitters can provide high color purity and high device efficiency, the high triplet energy (ET) of emitters often cause issues on long‐term device operation. In this work, as a solution to implementing stable operation of blue OLEDs, novel emission‐mechanism‐tuned MR type emitters were developed based on fused indolo[3,2,1‐jk]carbazole framework. The molecular structural changes effectively stabilized the ET while maintaining the narrow emission bandwidth. The fabricated blue fluorescent OLED recorded a highquantum efficiency in deep‐blue region of CIEy of 0.075 and device lifetime twice longer than a typical boron type dopant based device. This research establishes the emitter design strategy for extended blue OLEDs. [ABSTRACT FROM AUTHOR]

We are introducing an innovative organic semiconductor electroluminescent device capable of emitting light with unprecedented characteristics: high directionality (divergence angle of 1.1°) and high color purity (full width at half‐maximum of 2.5 nm). This achievement was realized through intricate design techniques aimed at enhancing gain via meticulous recombination zone control, complemented by the reduction of losses through minimizing the overlap of the optical mode with the electrodes. These groundbreaking results mark the world's first demonstration of simultaneously achieving a narrow spectrum and superior directionality in an organic electroluminescent device. [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]

Near ultraviolet (NUV) organic light‐emitting diodes (OLEDs) have great advantages in the field of light excitation sources, chemical and biological sensors, etc. However, the molecular design of NUV emitters still faces the challenges of spectral broadening and red‐shift. In this study, attaching weak oxygen‐bridged triarylboron acceptor to weak carbazolyl donor is able to address intractable problems by weakening donor–acceptor (D–A) charge transfer. Simultaneously, sterically wrapped and modified oxygen‐bridged triarylboron acceptor by bulk substituents (multiple carbazolyl) can suppress intermolecular π–π stacking through steric hindrance effect. These design strategies are able to obtain short‐wavelength, narrow‐band emission, and great color purity. As a result, carbazolyl derivatives xCz‐BO‐based (x = 2, 3, 4, 5) emitters show EL emission peaks from 406 to 422 nm in the NUV light region and small full‐width at half‐maximums (FWHMs) of 32–41 nm over a wide range of dopant concentrations (10–40 wt.%). The most violet Commission International de I'Eclairage (CIE) color coordinate is (0.16, 0.03). Moreover, 5Cz‐BO can be employed as host for vacuum‐/solution‐processed blue OLEDs and these devices exhibit high performance with EQEs of over 20%. [ABSTRACT FROM AUTHOR]

The combustion of mixed homogeneous pyrotechnic compositions and heterogeneous charges is studied experimentally with the aim of producing a selectable wavelength signal flare. The heterogeneous charge was perceived as a mixed color by a distant observer. A model for color chromaticity coordinates of homogeneous mixtures was derived that includes the mass, mass‐based burn rate and luminous intensity ratios of the constituting color compositions. This model can predict the expected dominant wavelength of a mixed composition. It can also handle the spacing of chromaticity coordinates of mixed compositions on a straight line in the CIE diagram between chromaticity coordinates of constituting colors. With two series of color composition mixtures, it was demonstrated that the chromaticity coordinates of the mixtures could be at, or slightly deviate, from the straight line connecting the chromaticity coordinates of the constituting compositions. It indicates there is little to no influence of flame temperature and mutual pyrotechnic reactions. [ABSTRACT FROM AUTHOR]

In the present system, Sm3+ activated Ba2BiV3O11 nanomaterial series radiating orange-red light was developed via an efficient approach of solution combustion method. The structural examinations using XRD analysis indicate that the sample is crystallized into the monoclinic phase with the P21/a (14) space group. The elemental composition and morphological conduct were studied via energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM) respectively. Also, the formation of nanoparticles was confirmed by transmission electron microscopy (TEM). Photoluminescent (PL) examinations reveal the orange-red emission from the developed nanocrystals via documenting the emission spectra, which reveals the peak at 606 nm due to the 4G5/2 → 6H7/2 transition. Further, the decay time, non-radiative rates, quantum efficiency, and band gap of the optimal sample were computed as 1.3263 ms, 219.5 s− 1, 70.88%, and 3.41 eV respectively. Finally, the chromatic parameters including color - coordinates (0.5565, 0.4426), 1975 K color correlated temperature (CCT), and color purity (85.58%) reflected their excellent luminous performance. The above-mentioned outcomes endorsed the relevancy of the developed nanomaterials as a propitious agent in the engineering of advanced illuminating optoelectronic appliances. [ABSTRACT FROM AUTHOR]

We have studied the optical and luminescence properties at room temperature of ultrathin colloidal semiconductor cadmium selenide nanoscrolls with a thickness of 2.5 monolayers. For colloidal synthesis of the objects under study, cadmium acetate dihydrate Cd(CH3COO)2·2H2O and trioctylphosphine selenide were used as precursors of cadmium and selenium, respectively, and solutions of oleic acid and octadecene were also used. Luminescence spectrum of cadmium selenide nanoscrolls was recorded using a fiber charge coupled device spectrometer. Spectrally resolved photoluminescence decays for nanoparticles were measured with the use of time-correlated single photon counting technique. The emission of the cadmium selenide nanoscrolls consists of interband and recombination luminescence bands. We found that the normalized photon numbers of recombination luminescence are larger than the normalized photon numbers of interband luminescence. We determined dominant wavelengths, chromaticity coordinates, and correlated color temperatures of ultrathin colloidal semiconductor cadmium selenide nanoscrolls. These ultrathin cadmium selenide nanoscrolls are promising for application in light-emitting diodes.

Microcavity structures are used in inorganic‐, organic‐, quantum‐dot‐, and perovskite‐based electroluminescent (EL) devices to advance next‐generation displays. However, there are difficulties in controlling electrical characteristics and patterning processes for producing different thicknesses for each red, green, and blue (RGB) subpixel, and the issues are more challenging in the high‐resolution display for future realistic media. Here, a novel design method is presented for a dual‐microcavity structure that controls high‐order modes of a second cavity stacked on top of EL devices with the same cavity length for each subpixel to produce multiple peaks at RGB resonant wavelengths. The dual‐microcavity effect demonstrated by top‐emitting organic light‐emitting diodes (OLEDs) can be conveniently fabricated via in situ deposition. By modulating the high‐order modes, the spectral characteristics of each RGB dual‐microcavity top‐emitting OLED (DMTOLED) are manipulated while its electrical properties are maintained. Green DMTOLED exhibits a maximum luminance of 2.075 × 105 cd m−2, allowing applications not only for commercialized displays but also for outdoor augmented reality and automotive displays. Furthermore, dual‐microcavity structures with narrow spectral bandwidths can be applied to next‐generation EL devices for more realistic media. The method is expected to be applied industrially, promoting the advancement of EL devices for next‐generation displays. [ABSTRACT FROM AUTHOR]

Magnesium aluminate spinel (MgAl2O4) (MAO) was fabricated by sol–gel process and sintered at a temperature ranging from 700 to 1400 °C. The phase development of MAO was confirmed by X-ray diffraction (XRD), Fourier transfer infrared spectroscopy (FTIR), and scanning electron microscopy. The XRD data confirms the formation of MAO spinel. FTIR analysis matches well with XRD data. The obtained results show that the optimized phase and morphology of the prepared nanoparticles were achieved at 1100 °C. The optical behavior of MAO was investigated using UV–Vis spectroscopy (UV–Vis) and fluorescence spectroscopy. Down-conversion energy transition from UV to visible light had been studied with three different excitations, 351 nm, 395 nm, and 405 nm. The material's color purity and CIE coordinates indicate that it is ideal for optoelectronic applications. [ABSTRACT FROM AUTHOR]

This study presents the synthesis of orange–red emitting Sr9Al6O18:Pr3+ nanophosphors (SAO:Pr3+ NPs) through the solution combustion process. Photoluminescence (PL) spectra revealed concentration quenching at 5 mol % with a critical distance of RC = 21.5 Å, indicating that electric multipolar interactions are responsible for the nonradiative energy transfer in the SAO lattice. Dexter's theory confirmed the quadruple–quadruple interaction as the mechanism behind the quenching. The optimized SAO:5Pr3+ NPs exhibited exceptional properties, including high color purity (CP = 94.2%), cost-effectiveness, eco-friendliness, scalability, and photostability. A fluorescence-based technique was developed using powder dusting to apply latent fingerprint (LFP) visualization and preservation. This method demonstrated high sensitivity, contrast, and no background interference, enabling the detection of LFPs over extended periods. Furthermore, lip prints (LPs), known for their sex differences and stability, have been effectively utilized for reliable and efficient forensic investigations. An unclonable invisible security ink was developed to combat counterfeiting, exhibiting high stability against UV light, aging, and physical abrasion. Mathematical models were employed for various fingerprint image processing tasks, including segmentation, normalization, ridge orientation estimation, ridge frequency estimation, Gabor filtering, binarization, thinning, and minutiae extraction. These algorithms were implemented by using a Python-based environment, resulting in enhanced fingerprints that displayed level I–II features. These findings underscore the potential applications of SAO:Pr3+ NPs in advanced forensic science and data security. This study offers insights into the synthesis, characterization, and application of SAO:Pr3+ NPs, highlighting their suitability for advanced forensic investigations, data security, and anticounterfeiting measures. [ABSTRACT FROM AUTHOR]

Over the past decade, thermally activated delayed fluorescence (TADF) emitters have garnered tremendous impetus because of their ability to harvest 100% excitons for the light emission in organic light emitting diodes (OLEDs). However, despite their superior external quantum efficiencies (> 35%), the broad emission spectra with associated full‐width‐at‐half maximum (FWHM > 70 nm) present a limiting factor that must be solved. Recently, multiple‐resonance TADF (MR‐TADF) materials based on the heteroatom doped polyaromatic hydrocarbons have gained astonishing attention owing to their remarkable narrowband emission (FWHM < 30 nm). However, emission of the majority of reported MR‐TADF emitters falls in the blue/green region, which inevitably jeopardizes their application in full‐color OLEDs. Therefore, there is an urgent need to develop the new molecular designs for expanding the color‐gamut of MR‐TADF emitters, i.e., λem > 550 nm without compromising the narrowband emission. To the best of current knowledge, no detailed reviews focusing on the different design strategies for producing long‐wavelength (> 550 nm) MR‐TADF emitters have been reported to date. To this end, a review highlighting the recent design advances for constructing long‐wavelength MR‐TADF emitters is presented, and their photophysics and OLED performance is discussed. Finally, the current status and future prospects of long‐wavelength MR‐TADF materials are discussed. [ABSTRACT FROM AUTHOR]

We investigated the combined effect of paired compositions of TiO2, MoO3 silencers, and CoO, NiO, K2Cr2O7+CuO, Fe2O3 dyes on the quality and optical-color characteristics of enamel coatings based on the matrix glass of the R2O--BaO--ZnO--A12O3--B2O3--TiO2--SiO2 system. It was established that in the presence of CoO, NiO, КгСг2О7+СиО dyes, the addition of MoO3 in the amount of up to 3 wt.% improved the quality of coatings, but did not lead to significant changes in the color tone, and only affected its shade. Introduction of Fe2O3 in the amount of up to 0.75 wt.% into the composition of the matrix glass, simultaneously combined with CoO, K2Cr2O7+CuO dyes, showed a similar pattern. The combination of Fe2O3 with NiO resulted in obtaining brown coatings of various shades characterized by =594--613 nm (orange region of the spectrum). The inexpediency of adding 15 wt.% TiO2 as a silencer for colored coatings based on the experimental matrix glass was established and the reasons for the absence of a silencing process at a firing temperature of 800°C were revealed. [ABSTRACT FROM AUTHOR]

The lighting characteristics of thermoplastic pyrotechnic compositions of various flames are studied. The emission spectrum of the blue flame composition doesn't depend on the nature of the color-forming component but is associated with copper monochloride formation in the combustion products. It was established that there are emission corresponding only to the emission spectrum of the initial compositions in the mixed compositions emission spectrum. Obtaining different color shades of flame lying on the line connecting the color points of the blue and green flames on the color diagram is possible by mixing the original compositions. [ABSTRACT FROM AUTHOR]

Progression in lighting sources mainly depended on new, robust energy‐efficient diodes due to their advanced photometric properties. All organic light‐emitting sources are constant energy‐efficient devices and will be the light of the future. We explore the potential of transition metal complexes by focusing on cobalt(II), nickel(II), and copper (II) with aminoguanidine naphthoate as white phosphors in organic light‐emitting diodes (OLEDs). The phosphors synthesized at optimized temperature were characterized structurally and thermally by spectral, thermal, and diffraction techniques. The photophysical studies of the target compound in several organic solvents having divergent polarity were also studied, and the results were exhibited. Photometric properties of the complexes were studied using photoluminescence, CIE (Commission internationale de l'éclairage) chromaticity coordinates, correlated color temperature, color purity, Duv, and TLCI (Television Lighting Consistency Index) to verify the applicability of complexes as phosphors. Excellent luminescence property with a high coloring index for (Cu(2NA‐AMG‐2H2O)) opens the advanced avenue for light sources and serves as vital constituents for light‐emitting diodes. [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]

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]

With tunable emission in the full visible region, the ecofriendly InP quantum dots (QDs) show unique application prospects in light-emitting devices. At present, InP QDs suffer from wide-bandwidth emission, especially for electroluminescence (EL), which hinders their applications in high-performance display devices. Here, we report a facile one-pot synthesis of narrow-bandwidth InP/ZnSeS/ZnS QDs using a safe phosphorus source of tris-(dimethylamino)-phosphine, in which the ZnSeS inner-shell layer is formed via temperature-gradient solution growth from 240 to 280 °C. The synthesized green QDs have a high photoluminescence quantum yield (PLQY) of 91% and full width at half-maximum (fwhm) of 36 nm. Moreover, the resultant quantum dot light-emitting devices (QLEDs) also show a narrow fwhm of 42 nm, which is the narrowest emission of green InP QLEDs based on a safe phosphorus source reported so far. Further modulation of the electron injection into the device by inserting a thin layer of lithium fluoride results in a peak external quantum efficiency of 5.56%. [ABSTRACT FROM AUTHOR]

In this research, the effects of solvent type, solvent to seed ratio, temperature and time of extraction on the yield, the color purity and the yield of bixin/norbixin of annatto were studied. Central Composite Design with 4 parameters including of solvent type (acetone, NaOH and acetone-NaOH), solvent to seed ratio (1:1 to 5:1 ml/g), time (2-6 h) and temperature of extraction (25-65 ºC) in three levels (-1, 0 and +1) was employed. The results indicated that the quadratic model was significant for the yield of annatto and R2 = 0.915, indicating that 91.5 % of the change in the responses could be predicted by the fitted model. In addition, the temperature and time of extraction had no any significant effect on the extraction yield. The maximum yield was predicted by NaOH under the 46.41 ºC, 2.05 h and solvent to seed ratio of 5:1, which was 13.31 %. The quadratic model was significant for the color purity of annatto and R2 = 0.848. By changing the solvent from acetone to NaOH and increasing the solvent to seed ratio, the color purity increased. Furthermore, bixin/ norbixin yield, which is the weight ratio of bixin or norbixin to annatto seed, was determined and calculates as a comprehensive response. The most effective factor in the color change of annatto powder was determined as light and if it removed, using suitable packaging, it would be possible to maintain the best quality of the powder .Similar results were obtained regarding the stability of annatto dye in the whey powder. [ABSTRACT FROM AUTHOR]

A series of heteroleptic terbium(III) complexes with fluorinated 2‐thenoyltrifluoroacetone (TTFA) and other heteroaromatic units have been synthesized. The developed heteroleptic complexes were inspected via elemental study, cyclic voltammetry, thermal analysis and spectroscopic investigations. Optical band‐gap data proposed the conducting property of prepared complexes. The photoluminescence emission profiles illustrated peaks based on terbium(III) cation (Tb3+) positioned at ~617, 586, 546 and 491 nm, imputed to 5D4 to 7FJ (J = 3,4,5,6) transitions separately. Most intense peak at 546 nm corresponding to 5D4 → 7F5 transition is accountable for the green emissive character of developed complexes. The luminous character of complexes reveals the sensitization of Tb3+ by ligands. Color parameters further corroborates the green emanation of Tb3+ complexes. The photometric characteristics of complexes recommended their usages in designing display devices. [ABSTRACT FROM AUTHOR]

Abstract A common full-color method involves combining micro-light-emitting diodes (LEDs) chips with color conversion materials such as quantum dots (QDs) to achieve full color. However, during color conversion between micro-LEDs and QDs, QDs cannot completely absorb incident wavelengths cause the emission wavelengths that including incident wavelengths and converted wavelength through QDs, which compromises color purity. The present paper proposes the use of a recycling-reflection color-purity-enhancement film (RCPEF) to reflect the incident wavelength multiple times and, consequently, prevent wavelength mixing after QDs conversion. This RCPEF only allows the light of a specific wavelength to pass through it, exciting blue light is reflected back to the red and green QDs layer. The prototype experiment indicated that with an excitation light source wavelength of 445.5 nm, the use of green QDs and RCPEFs increased color purity from 77.2% to 97.49% and light conversion efficiency by 1.97 times and the use of red QDs and RCPEFs increased color purity to 94.68% and light conversion efficiency by 1.46 times. Thus, high efficiency and color purity were achieved for micro-LEDs displays. Graphical Abstract

• 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]

This study aimed to incorporate MnFe 2 O 4 nanoparticles into a nanocomposite blend of poly (methyl methacrylate, PMMA), polyethylene oxide (PEO), and polyaniline (PANi). The incorporation was achieved using straightforward, environmentally friendly, and cost-effective techniques. The structures of MnFe 2 O 4 and PMMA/PEO/PANi/x wt % MnFe 2 O 4 were examined using X-ray diffraction (XRD) and/or transmission electron microscopy (TEM) techniques. The diffused reflectance technique was employed to investigate the linear optical properties of all blends, including absorbance, transmittance, reflectance, extinction coefficient, linear refractive index, optical dielectric constant and optical conductivity. PMMA/PEO/PANi blend has direct and indirect energy gaps of 5.33 and 4.65 eV, respectively. As MnFe 2 O 4 doping level increased to 2.5 wt%, the smallest direct and indirect energy gap values of 5.16 and 4.08 eV were obtained, respectively. The addition of 1 wt% MnFe 2 O 4 to the blend increased the refractive index value at 600 nm to 2.24. Nonlinear optical parameters of PMMA/PEO/PANi/x wt% MnFe 2 O 4 blends were calculated. The emitted colors and their purities of all blends were investigated as a function of MnFe 2 O 4 concentration. The obtained results suggested that the PMMA/PEO/PANi/x wt% MnFe 2 O 4 blends may be used in a variety of optoelectronic and storage applications. • PMMA/PEO/PANi/x wt% MnFe 2 O 4 blends were synthesized using casting method. • Doped blends exhibited high UVA, UVB and UVC spectra absorbance. • The optical band gap values of the host blend exhibited irregular reduction. • The blends exhibited different degrees of blue colors. • The irregular decrease in energy density of the PMMA/PEO/PANi blend was obtained as a result of doping. [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]

ZnO and cerium-doped ZnO on a glass substrate have been prepared by the sol–gel method using the spin coating technique and water bath growth process. Ce-doping concentration on film structure, morphology, and optical properties is investigated. The result indicated that the hexagonal wurtzite ZnO with high crystalline quality formed on the substrate. The crystal parameters a and c decreased, crystal size increased, and the compressive strain formed after Ce-doping. Formed un-, 3%, 6%, 12% Ce-doped ZnO film has a spherical shape with a size between 8.6–31, 14–52, 18–56, and 20–91 nm, respectively. All films had good absorption of 300–400 nm ultraviolet light, in particular, the absorption of near ultraviolet (370–400 nm) increased after doping of Ce. The transmittance of light between 400–800 nm decreased with Ce-doping concentration. The band gap energy increased after Ce-doping reaching better optical behavior for preparing ZnO heterostructured thin-film. All film emitted intense blue emission under 375 nm excitation at room temperature. This indicated the film can have application in optoelectronic devices. [ABSTRACT FROM AUTHOR]

This article presents four ternary terbium complexes based on fluorinated 2-thenoyltrifluoroacetone (TTFA) and N donor bidentate neutral ligands. The prepared complexes were examined by elemental study, electrochemical analysis, spectroscopically and thermo-gravimetrically. Spectral analysis shows the bonding of Tb3+ ion with oxygen and nitrogen atom of diketone and neutral ligand respectively. Upon excitation in UV region, synthesized terbium complexes show luminescence in green region of electromagnetic spectrum. Photoluminescence emission spectra of complexes do not show any ligand based peak suggesting the effective transferal of energy from ligand to metal ion. Green emanation by terbium complexes is owing to intense peak ~547 nm (5D4 → 7F5). The outcome of emission data and CIE coordinates correlate with each other and affirms the utility of green luminous complexes as potential emissive material for optoelectronic gadgets applied in lighting system. [ABSTRACT FROM AUTHOR]

A series of Eu2+-activated Sr3LnM(PO4)3 F(Ln = Gd, La, Y; M = Na, K) phosphors were synthesized by high-temperature solid-phase method. The phase structure, morphology and luminescence characteristics of the samples were characterized by X-ray diffraction, scanning electron microscopy, fluorescence spectroscopy and other test methods. The experimental results demonstrate that the phosphor Sr3LnM(PO4)3F∶Eu2+ was successfully synthesized, and the particle size of the sample ranges from 2 μm to 10 μm. The phosphor has strong emission in the blue-light region, which is attributed to the 4f6 5d→4f7 transition of the luminescent center Eu2+. The emitting color of Eu2+ changes from light blue to dark blue and the color purity increases after the transformation of Na to K, which effectively regulates the luminescence of Eu2+ in fluorapatite Sr3LnM(PO4)3F. A new strategy by substituting of the secondary layer coordination atom is found to regulate the phosphors color of Eu2+. [ABSTRACT FROM AUTHOR]

• Gel-combustion method was used to produce triclinic structure based Sm3+ doped Y 2 Si 2 O 7 nanophosphors. • Sm3+ ions occupied the sites in Y 2 Si 2 O 7 lattice without inverted symmetry. • Dipole-quadrupole interactions responsible for quenching within the host lattice. • The band gap value of YPS:4 mol % Sm3+ was determined to be 5.67 eV. • The optimal phosphor demonstrates good thermal characteristics with high activation energy of 0.2314 eV. This study illustrates the development of a reddish-orange radiating Sm3+-activated Y 2 Si 2 O 7 (YPS) nanophosphor through a gel-combustion technique. We thoroughly examined the phase purity, elemental composition and luminous characteristics of synthesized Y 2 Si 2 O 7 :Sm3+ phosphors. XRD peaks are aligned with standard card (38–0223), based to X-ray diffraction pattern. The triclinic cell with the space group P-1 (No. 2) provides the crystal structure. The impeccable morphology of the particles with their varied shape and nanoscale size is confirmed by TEM investigations. EDX analysis verified the fabrication of the product with correct stoichiometry. Tauc's model was implemented to assess optical energy for host and optimal sample, which demonstrated the high optical eminence of produced materials. The emission profiles exhibit three distinct peaks at an excitation of 408 nm: 566, 604 and 645 nm, which correspond to the 4G 5 / 2 →6H J / 2 (J = 5, 7 and 9) transitions, correspondingly. Observations from experiments reveal that 4 mol % is the optimal Sm3+ doping level and the dipole-quadrupole interaction among activated ions define concentration quenching process. The phosphor YPS:4 mol % Sm3+ demonstrates good thermal characteristics, with high activation energy of 0.2314 eV. Y 2 Si 2 O 7 :Sm3+ phosphors contain CIE coordinates in the reddish orange region of CIE chart and having high color purity, which reflect its excellent applicability for the white light emitting diodes. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel red-emitting Ca 2 EuMO 6 double-perovskite phosphors were prepared by solid-state reaction method. • Under 395 nm excitation, these phosphors produced bright red emissions around 620 nm. • High color purity of 90.7%, 93.2%, and 92.7% was achieved for M = Sb, Nb, Ta, respectively. • These phosphors also exhibited excellent thermal stability. In this paper, three new efficient Eu3+-activated Ca 2 EuMO 6 (M = Sb, Nb, and Ta) red-emitting phosphors with outstanding luminescence properties were prepared by using the high-temperature solid-state reaction method. X-ray diffraction and Rietveld refinements revealed the double-perovskite structure of Ca 2 EuMO 6 (M = Sb, Nb, and Ta) compounds. Photoluminescent excitation and emission spectra, decay lifetimes, CIE chromaticity coordinates, color purity values, internal quantum efficiency, and thermal stability were discussed in detail. Under the excitation of 395 nm near-ultraviolet light, these Ca 2 EuMO 6 (M = Sb, Nb, and Ta) phosphors demonstrated bright narrow-band red emissions with peaks at 592, 620, 656, and 703 nm due to the 5D 0 →7F J (J = 1–4) transitions of Eu3+ ions. The internal quantum efficiencies of the Ca 2 EuSbO 6 , Ca 2 EuNbO 6, and Ca 2 EuTaO 6 samples were determined to be 39.3%, 41.6%, and 40.4%, respectively. Impressively, the emission intensity of Ca 2 EuNbO 6 is about 1.25 times higher than that of commercial Y 2 O 3 :Eu3+ red phosphor. CIE color coordinates of Ca 2 EuMO 6 (M = Sb, Nb, and Ta) phosphors were calculated to be (0.6748, 0.3250), (0.6800, 0.3198), and (0.6790, 0.3208), respectively; along with high color purity of 90.7%, 93.2%, and 92.7%. Besides, their thermal stability was also investigated, and the corresponding emission intensities of Ca 2 EuMO 6 (M = Sb, Nb, and Ta) at 423 K were respectively maintained at 73%, 86%, and 80% of that at 303 K. All results show that these newly developed red-emitting Ca 2 EuMO 6 (M = Sb, Nb, and Ta) phosphors possess potential applications in white light-emitting diodes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cool white light emissive Y 2 Si 2 O 7 :Dy3+ developed via gel-combustion method, having triclinic crystal structure with P-1 space group. • NUV 352 nm excitation produced different emission peaks of Dy3+ ions, analogous to 4F 9/2 →6H 15/2, 13/2 and 11/2 transitions. • Quadrupole-quadrupole interaction responsible for concentration quenching. • Optimum sample maintain luminescence stability 80.4 % upto 423 K temperature with 0.2503 eV of activation energy. We report on development and properties of Dy3+ doped Y 2 Si 2 O 7 (YPS) phosphor, a key development in efficient, sustainable lighting via phosphor converted white light emitting diodes (pc-wLEDs). Using gel-combustion method, we synthesized a series of Y 2-x Si 2 O 7 :xDy3+ (x = 1–8 mol %) phosphors. The prepared samples were characterized for their structure, morphology and elemental composition using X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) respectively. Diffraction exploration verified triclinic structure and phase purity of fabricated samples. TEM image displayed particle agglomeration with nearly spherical structures. Optical parameters were assessed through diffuse reflectance spectrum (DRS) and photoluminescence (PL) spectra analysis. On 352 nm excitation, distinct luminous peaks from Dy3+ ions, analogous to 4F 9/2 →6H M (M = 15/2, 13/2, and 11/2) transitions, were observed. Particularly, intense emission at 571 nm resulted from the 4F 9/2 →6H 13/2. The optimal amount of Dy3+ was determined to be 5 mol %, with concentration quenching attributed to quadrupole–quadrupole interaction. Y 1.95 Si 2 O 7 :5 mol % Dy3+ phosphor possessed activation energy of 0.2503 eV and demonstrates good thermal stability. Thus, these results indicate that the synthesized Y 2 Si 2 O 7 :Dy3+ phosphors are well suited for white light applications. [ABSTRACT FROM AUTHOR]

• Highly efficient Li 2 MgTi 3 O 8 :Eu3+ phosphors have been synthesized for the first time by solid state reaction method. • Li 2 MgTi 3 O 8 :Eu3+ phosphors have an intense emission at 615 nm corresponding to red light upon 398 nm excitation. • The prepared phosphor possesses high color purity and warm CCT values. • Li 2 MgTi 3 O 8 :Eu3+ phosphors have the potential to be used as a red component in pc-WLEDs under UV excitation. In search of efficient and suitable phosphors for white light emitting diodes (w -LEDs), herein, we report Li 2 MgTi 3 O 8 :Eu3+ as red phosphors that are low-cost eco-materials synthesized by solid-state reaction method. XRD patterns confirm the crystallinity and phase purity of the as-prepared phosphors with the successful incorporation of Eu3+ ions. FTIR, FE-SEM and TEM were used to understand the functional groups and morphology of prepared samples respectively. The band gap energy calculated from DRS showed Burstein–Moss effect. Under 398 nm excitation, intense red emission was recorded at 615 nm and lifetime values were in microsecond range. The prepared phosphor possesses quantum efficiency of 31.74%, good thermal stability with an activation energy of 0.254 eV and exhibit warm red emission with 100% color purity. Therefore, the obtained results suggests that the prepared Li 2 MgTi 3 O 8 :Eu3+ phosphors can be considered as an appropriate candidate for the red component in w- LEDs. [Display omitted] [ABSTRACT FROM AUTHOR]

• Red warm light emitting LaSr 2 AlO 5 :Eu3+ phosphors have been generated through gel combustion approach. • LaSr 2 AlO 5 :Eu3+ crystallized into tetragonal crystal structure with symmetry group of I4/mcm. • The emission intensity of electric dipole 5D 0 →7F 2 transition is significantly larger than that of magnetic dipole 5D 0 →7F 1 transition which suggested the presence of Eu3+ at low symmetry locations and produced intense red emission. • LaSr 2 AlO 5 :0.04Eu3+ sample was emitted red light with high thermal stability. Red-emitting La 1-x Sr 2 AlO 5 :xEu3+ (x = 0.01–0.06) phosphors have been synthesized via gel combustion (GC) approach and their structure and luminescent characteristics were analyzed in detail. The tetragonal crystal structure (I4/mcm space group) of all generated La 1-x Sr 2 AlO 5 :xEu3+ (x = 0.01–0.06) phosphors have been established by X-ray diffraction and rietveld analysis. The shape and size of the phosphor has been examined using transmission electron microscopy (TEM) and the estimated crystallite size was found to be 32–65 nm. Energy Dispersive X-ray (EDX) analysis confirmed the chemical composition of the synthesized materials. The diffuse reflectance spectra (DRS) were used to compute the band gap energies (E g) of the samples which emerged to be in region of 5.373–6.009 eV. The Eu3+ activated LaSr 2 AlO 5 phosphors produce red emissions at 579, 592, 614, 656 and 708 nm, when excited at 395 nm. These emission bands are caused by 5D 0 →7F J (J = 0, 1, 2, 3, 4) electronic transitions of Eu3+ ion. The Judd-Ofelt theory further supports the performance of LaSr 2 AlO 5 :Eu3+ phosphors as a red emitting substance with high branching ratio corresponding to 5D 0 →7F 2 transition from Eu3+ center present in the low symmetry site. Computed chromaticity coordinates (x, y) indicate a high degree of color purity in the phosphors, providing additional evidence for the presence of red emission. Temperature dependent emission (PL) spectra revealed good thermal stability of the synthesized nanophosphors with activation energy (E a) of 0.1384 eV. [Display omitted] [ABSTRACT FROM AUTHOR]

A gel-combustion approach, utilizing urea as a fuel has been employed to generate highly green luminous LaSr 2 AlO 5 :Tb3+ nanophosphors. This experiment explored the crystal structure, chemical content, phase purity, morphology, band gap, photoluminescence characteristics and thermal quenching process of the synthesized materials. The tetragonal structure of the synthesized material which comprises the I 4/ mcm (140) space group is supported by the X-ray diffraction data. The agglomerated particles exhibited almost uniform morphology and crystallite diameters between 45 and 65 nm, supported by SEM and TEM analyses. The band gap of LaSr 2 AlO 5 (5.97 eV) and optimum La 0.97 Sr 2 AlO 5 :3 mol % Tb3+ (5.61 eV) classify it as direct band gap material. The LaSr 2 AlO 5 :Tb3+ phosphors displayed a green emission peak at 543 nm (5D 4 →7F 5 transition) after being stimulated at 252 nm. LaSr 2 AlO 5 :Tb3+ phosphor has an optimum doping concentration of x = 3 mol %. The average decay time of the excited state of all samples has been determined from the double exponential fitting results of the decay curves obtained from PL at 252 nm and 543 nm of excitation and emission wavelengths respectively. With activation energy of 0.1838 eV, this phosphor exhibits excellent temperature stability. The CIE coordinates show the presence of emitted light with high color purity in the green region of visible spectrum. All the results of present research endorse the applicability of LaSr 2 AlO 5 :Tb3+ nanophosphors as a green component for displays and other lighting applications. [Display omitted] • A series of green light emitting LaSr 2 AlO 5 :Tb3+ nanophosphors have been synthesized through gel-combustion method. • LaSr 2 AlO 5 :Tb3+ crystallized into tetragonal crystal structure with symmetry group of I 4/ mcm. • On 252 nm excitation, LaSr 2 AlO 5 :Tb3+ phosphors exhibit green emission peak at 543 nm corresponds to the 5D 4.→7F 5 transition. • The band gap value of La 0.97 Sr 2 AlO 5 :3 mol % Tb3+ was determined to be 5.61 eV. • Photometric and thermal analysis of the synthesized samples validates their applicability in display applications. [ABSTRACT FROM AUTHOR]

Multi-resonance thermally activated delayed fluorescence (MR-TADF) materials, based on polycyclic aromatic frameworks, have shown promise in achieving narrow-band emission and high luminous efficiency. In this study, we investigate the performance of a blue MR-TADF material, 2′2'2''-(1,3,5-triazine-2,4,6-triyl) tris(9-(2-(naphthalen-2-yl)phenyl)-9H-carbazole) (TBN-TPA), in tandem OLED devices. Single emitter unit and two emitter unit tandem OLED devices with blue MR-TADF material were explored with optical modeling simulation. More importantly, the tandem architecture assists in realizing narrow-band emission and high color purity via optical interference and microcavity effects, which are essential for meeting BT 2020 standards. TBN-TPA achieves narrow full width at half maximum down to 24 nm and CIE coordinates approaching the blue region in tandem devices. Our work highlights the significant advantages of combining tandem architectures and emerging MR-TADF emitters for developing high-performance OLEDs with both high efficiency and wide color gamut. This is the first demonstration of using tandem OLED architecture to improve both efficiency and color purity of a blue multi-resonance TADF emitter. Further research on optimizing tandem structures and designing advanced MR-TADF materials will promote the applications of OLED displays. • Single-emissive and dual-emissive layer blue MR-TADF tandem OLED devices were explored with optical modeling simulation. • The tandem architecture assists in realizing narrow-band emission and high color purity via optical interference and microcavity effects with a narrow FWHM of 24 nm and CIE coordinates approaching the blue region in tandem devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bright red-emitting Ca 2 LuZr 2 Al 3 O 12 :Eu3+ phosphors are prepared. • They exhibit intense red emissions around 618 nm. • Color purity reaches 91.1%. • Thermal stability is excellent. In this work, a group of red-emitting Ca 2 LuZr 2 Al 3 O 12 : x Eu3+ (x = 20%, 30%, 40%, 50%, 60%, 70% and 80%) phosphors have been prepared and their luminescence properties are studied. X-ray diffraction, excitation and emission spectra, fluorescence decay curves, CIE color coordinates, and temperature-dependent photoluminescence spectra are used to characterize these samples. All these Ca 2 LuZr 2 Al 3 O 12 :Eu3+ compounds exhibit intense red luminescence peaking at around 618 nm under 394 nm excitation. The critical concentration of Eu3+ ion is 50 mol%, and the concentration quenching mechanism has been discussed and analyzed. The CIE color coordinates of the optimal Ca 2 LuZr 2 Al 3 O 12 :50%Eu3+ sample are (0.6506, 0.3487), and it has a high color purity of 90.7%. Importantly, the emission intensity of Ca 2 LuZr 2 Al 3 O 12 :50%Eu3+ is about 1.67 times higher compared to the commercial Y 2 O 3 :Eu3+ red phosphor. What's more, Ca 2 LuZr 2 Al 3 O 12 :50%Eu3+ phosphor also displays excellent resistance to thermal quenching at elevated temperature; only 14% emission intensity is lost at 150 °C. [ABSTRACT FROM AUTHOR]

In this study, the green emitting phosphors of Gd 4 O 3 F 6 :Yb3+ and GdOF:Yb3+ were prepared by co-precipitation & hydrothermal methods, and then annealed in air atmosphere at 700 °C and 750 °C respectively. The influence of annealing temperature and Yb3+ doping amount on the crystal phase and luminescent properties of the products were explored in detailed through characterization by XRD, TEM,SEM, XPS, Raman spectra, luminescence spectra. The XRD results indicate that the target products Gd 4 O 3 F 6 :Yb3+(JCPDS No.26-0658) and GdOF:Yb3+ (JCPDS No.50-0569) can form a single crystal phase at annealing temperatures of 700 °C and 750 °C, respectively, and no new impurity crystal phase was introduced with the increase of Yb3+ doping amount. Meanwhile, the XRD results also proved that Yb3+ successfully entered the lattice by replacing Gd3+, and the XPS results confirm the presence of Gd, F, O, Yb, Er in the product. In addition, the luminescence spectrum shows that with the doping of Yb3+, the target products Gd 4 O 3 F 6 : Yb3+ and GdOF: Yb3+ exhibit excellent luminescence properties and emit characteristic peaks of Er3+. The optimal doping amount of Yb3+ in both products is 5.0%, and the luminescence intensity of Gd 4 O 3 F 6 :5.0% Yb3+ is significantly higher than that of GdOF: 5.0% Yb3+. Moreover, the UC mechanisms were elucidated through the laser power dependence of the UC emissions. The color coordinates of Gd 4 O 3 F 6 : 5.0% Yb3+ was determined as (0.2719, 0.7165), and the color purity reached 99.89%. • Single crystal phase Gd 4 O 3 F 6 : Yb3+ and GdOF: Yb3+ products were prepared. • Under 980 nm excitation, Gd 4 O 3 F 6 : 5.0% Yb3+ can emit green light efficiently. • The Gd 4 O 3 F 6 of monoclinic crystals is more favorable for UC emission than the GdOF crystals of rhombohedra. • The color purity of the Gd 4 O 3 F 6 : 5.0% Yb3+ product reached 99.89%. [ABSTRACT FROM AUTHOR]

A series of Sm3+-activated Ca 3 Gd(AlO) 3 (BO 3) 4 red-emitting phosphors were prepared by a traditional high-temperature solid-state approach. They were characterized by XRD refinements, TEM, SEM, EDS, DRS, FTIR, Raman spectra, photoluminescence (PL) spectra, and fluorescence decay curves. The microstructure of the cation-borate phosphors and the presence of Sm3+ dopants, and their impact at the Ca and Gd sites were studied. All the samples exhibited bright red emissions caused by intra-4f transitions of Sm3+ ions when excited at 404 nm. The optimum dopant concentration was 4mol%, and the concentration quenching (CQ) process was driven by dipole-dipole interaction using Inokuti-Hirayama, and Dexter theories. Interestingly, the temperature-dependent PL spectra manifested that the resulting phosphor had excellent thermal stability with an activation energy of 0.234 eV. Ultimately, the investigated phosphor demonstrated excellent chemical stability. The Sm3+-doped CGAB:Sm3+ phosphor can convert NUV LED chips into intense red emission with Commission Internationale de l'Eclairage (CIE) diagrams of 0.615, 0.382 and high color purity of up to 95.6%. The WLED containing CG 0.96 AB:0.04Sm3+ merged with the commercial phosphors revealed low correlated color temperature (CCT≈4197 K) and high color rendering index (CRI≈89.7). EL spectrum of the fabricated Red-LED device. Inset exemplifies the coordination diagram and image for the red phosphor. UV excitation induced bright red emissions with high color purity and outstanding thermal-quenching (TQ) resistance. Luminescent pictures of the prepared Red–LED and White-LEDs device with the input current.▪ • UV excitation induced bright red emissions with high color purity up to 95.6%. • They possessed good chemical stability in an existing environment. • The CG 0.96 AB:0.04Sm3+ exhibited outstanding thermal-quenching (TQ) resistance of>90.8%. • Red LED and WLED devices were fabricated by using phosphor and UV LED chips. [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]

A common full-color method involves combining micro-light-emitting diodes (LEDs) chips with color conversion materials such as quantum dots (QDs) to achieve full color. However, during color conversion between micro-LEDs and QDs, QDs cannot completely absorb incident wavelengths cause the emission wavelengths that including incident wavelengths and converted wavelength through QDs, which compromises color purity. The present paper proposes the use of a recycling-reflection color-purity-enhancement film (RCPEF) to reflect the incident wavelength multiple times and, consequently, prevent wavelength mixing after QDs conversion. This RCPEF only allows the light of a specific wavelength to pass through it, exciting blue light is reflected back to the red and green QDs layer. The prototype experiment indicated that with an excitation light source wavelength of 445.5 nm, the use of green QDs and RCPEFs increased color purity from 77.2% to 97.49% and light conversion efficiency by 1.97 times and the use of red QDs and RCPEFs increased color purity to 94.68% and light conversion efficiency by 1.46 times. Thus, high efficiency and color purity were achieved for micro-LEDs displays. [ABSTRACT FROM AUTHOR]

Herein, we designed Er3+-incorporated zincate-based nanomaterials via a rapid, low-cost, and environmentally friendly urea-combustion route. X-ray powder diffraction (XRPD) profiles revealed their orthogonal crystalline structure. Electron microscopy showed nanoscale (48–70 nm) non-uniform agglomerated particles. The presence of [BaO11] and [ZnO5] structural units in the present samples was shown by Fourier-transform infrared (FT-IR) spectroscopy. Emission spectra yielded a characteristic peak at 551 nm, which contributed to their bright-green light. The optimal nanomaterial had 3.0 mol% of Er3+ content, and it exhibited excellent bright-green light. Exchange-type multipolar inter-linkages via cross-relaxation predominantly direct the quenching of luminescence post x = 0.03 Er3+ content, as shown by the Inokuti-Hirayama (I-H) model. The optical bandgap and Urbach energy were obtained from experimental data-fitting with Tauc's hypothesis and an empirical correlation. Excellent color-purity (87.86%) and color temperature (6916 K) with chromaticity coordinates (0.2531, 0.6106) of the optimized nanomaterial were similar to National Television Standards Committee (NTSC) and NICHIA Corporation fabricated light-emitting diode (LED) green standards. Hence, the developed nanomaterials appear to be a good candidates for generating cool-green light in high-performance blue/green/red (B/G/R) white-light-emitting diodes (wLEDs), sensors, and laser applications. [ABSTRACT FROM AUTHOR]

The fluorescent molecule N,N-bis(3',5'–bis(trifluoromethyl)-[1,1'–biphenyl]-4–yl)perylen-3-amine (TFPA) was designed and synthesized by introducing the strong electron-withdrawing trifluoromethyl group and the strong electron-donating diphenylamino group, with perylene as the core. The structure of the target product was identified by nuclear magnetic resonance, and its UV–vis absorption properties, fluorescence emission properties, quantum yield and lifetime were studied systematically. The results showed that the HOMO of TFPA was mainly localized in the perylene part with a small part localized in the triphenylamine structure. The LUMO was almost localized in the perylene part. Therefore, the ground-state absorption of TFPA is mainly attributed to the π–π* transition accompanied by with little the slight intramolecular charge transfer effect. The maximum emission peak (534 nm) of TFPA in the solid state was 18 nm redshifted compared to that of TFPA in solution (516 nm). TG results show that TFPA still does not decompose at 300 ℃, indicating good thermal stability. In addition, a yellow-light-emitting diode device based on the fluorescent molecule TFPA was constructed (CIE coordinates: 0.45, 0.54). The LED device showed good color purity (color purity: 97.8%). The results showed that TFPA was a luminescent material with excellent thermal stability and high color purity and had potential for use in fabricating yellow LEDs. [ABSTRACT FROM AUTHOR]

Donor−acceptor molecules with hybridized local and charge transfer (HLCT) excited state have been demonstrated to be an efficient strategy for achieving high performance electroluminescence by harvesting both singlet and triplet excitons. In this study, a series of bipolar D−A molecules with twisted bridge are synthesized and these chromophores exhibit good thermal, morphological and photophysical properties, electrochemical stabilities as well as HLCT excited state features. Excellent deep‐blue electroluminescence (EL) performances are achieved using CSiTPI (external quantum efficiency (EQE) of 7.1% and CIEx,y coordinates of (0.16, 0.06) in a nondoped OLED) and DSiTPI (EQE of 7.4% and CIEx,y of (0.16, 0.05) in a doped OLED) as emitters with small full width at half maxima (FWHM, 45−48 nm). Devices using DSiTPI and CSiTPI as hosts are also fabricated and all the devices show high EL performances and small efficiency roll‐offs. A green device with DSiTPI acquires maximum current, power, and EQE of 78.5 cd A−1, 72.5 lm W−1, and 20.8%. The research demonstrates that excellent deep‐blue EL performances with good color purity can be achieved using D−A emitters with highly twisted bridge in HLCT OLEDs. [ABSTRACT FROM AUTHOR]

Oxyfluoride (P2O5-Bi2O3-Na2CO3-SrCO3-ZnF2-Eu2O3) glasses of different dopant (Eu3+) ion concentrations were synthesized by the traditional melt quenching method. Optical absorption, luminescence and lifetime measurements were performed with UV-Vis and PL techniques. A total of six absorption bands were observed in the wavelength range 200-800 nm, including one intense high band at 392 nm was assigned to 7F0→5L6 transition. The covalency between the host environment and Eu3+ ion was noticed with the measured nephelauxetic ratios (β) and bonding parameters (δ). The energies of the energy band gaps (Eg) and Urbach (ΔE) were estimated from the Tauc's plots, drawn from the absorption spectra. Luminescence spectra exhibited the prominent reddish-orange emission at 612 nm due to the 5D0→7F2 characteristic transition of Eu3+ ion. The lasing (radiative) parameters of f-f transitions of the Eu3+ ion was evaluated using the Judd-Ofelt intensity parameters (Ω2, Ω4, and Ω6). The higher magnitude of branching ratios (βexp) suggests the suitability of the present glass. The decay profile for the 5D0 level of europium was recorded by monitoring the emission and excitation wavelengths 612 & 392 nm, respectively. The color temperature and purity were calculated using CIE 1931 color coordinates. The emission color band spectra have also been recorded. [ABSTRACT FROM AUTHOR]