International Commission On Illumination Research Articles

High-Performance Ultraviolet Organic Light-Emitting Diodes Enabled by Double Boron-Oxygen-Embedded Benzo[m]tetraphene Emitters.

Ultraviolet organic light-emitting diodes (UV OLEDs) have attracted increasing attention because of their promising applications in healthcare, industry, and agriculture; however, their development has been hindered by the shortage of robust UV emitters. Herein, we embedded double boron-oxygen units into nonlinear polycyclic aromatic hydrocarbons (BO-PAHs) to regulate their molecular configurations and excited-state properties, enabling novel bent BO-biphenyl (BO-bPh) and helical BO-naphthyl (BO-Nap) emitters with hybridized local and charge-transfer (HLCT) characteristics. They could be facilely synthesized in gram-scale amounts via a highly efficient two-step route. BO-bPh and BO-Nap showed strong UV and violet-blue photoluminescence in toluene with full width at half-maximum values of 25 and 37 nm, along with quantum efficiencies of 98 and 99%, respectively. A BO-bPh-based OLED showed high color purity UV electroluminescence peaking at 394 nm with Commission Internationale de l'Eclairage (CIE) coordinates of (0.166, 0.021). Moreover, the device demonstrated a record-high maximum external quantum efficiency (EQE) of 11.3%, achieved by successful hot exciton utilization. This work demonstrates the promising potential of double BO-PAHs as robust emitters for future UV OLEDs.

High-performance deep-blue electroluminescence from multi-resonance TADF emitters with a spirofluorene-fused double boron framework.

The development of multi-resonance thermally activated delayed fluorescence (MR-TADF) materials in the deep-blue region is highly desirable. A usual approach involves constructing an extended MR-TADF framework; however, it may also intensify aggregate-caused quenching issues and thereby reduce device efficiency. In this study, we develop a molecular design strategy that fuses the MR-TADF skeleton with 9,9'-spirobifluorene (SF) units to create advanced deep-blue emitters. The SF moiety facilitates high-yield one-shot bora-Friedel-Crafts reaction towards an extended skeleton and mitigates interchromophore interactions as a steric group. Our findings reveal that orbital interactions at the fusion site significantly influence the electronic structure, and optimizing the fusion mode allows for the development of emitters with extended conjugation length while maintaining non-bonding character. The proof-of-concept emitter exhibits narrowband emission in the deep-blue region, a near-unity photoluminescence quantum yield, and a fast k RISC of 2.4 × 105 s-1. These exceptional properties enable the corresponding sensitizer-free OLED to achieve a maximum external quantum efficiency (EQEmax) of 39.0% and Commission Internationale de l'Eclairage (CIE) coordinates of (0.13, 0.09). Furthermore, the hyperfluorescence device realizes an EQEmax of 40.4% with very low efficiency roll-off.

Spirobifluorene-fused strategy enables pure-green multiple resonance emitters with low efficiency roll-off.

Herein, we present a molecular design strategy centered on the spiroannulation of the MR-core skeleton to fabricate green MR-emitters and reduce device efficiency roll-off. Fusing 9,9'-spirobifluorene into the central framework of MR-emitters facilitates the distribution of the highest occupied molecular orbital (HOMO) across the spiro units, leading to a red-shifted emission and giving rise to a pure-green MR-emitter (DPhCz-SFBN) with the Commission Internationale de l'Eclairage (CIE) coordinates of [0.16, 0.74] in toluene solution, closely matching the BT.2020 standard for green. Additionally, the resultant highly twisted hetero[6]helicene conformation and a nearly perpendicular conformation of spirocycle structure effectively minimize close π-π stacking interactions among the MR-emitting cores, thereby reducing exciton quenching. Consequently, organic light-emitting diodes (OLEDs) based on DPhCz-SFBN exhibit a high maximum quantum efficiency (EQEmax) of 32.8% with low efficiency roll-off, maintaining an EQE of 23.2% at a practical luminance level of 5000 cd m-2.

Donor engineering to regulate fluorescence of a symmetrical structure based on a fluorene bridge for white light emission.

A white organic light-emitting device (WOLED) obtained using blue and yellow complementary colors possesses extremely high optical efficiency. We designed and prepared a completely symmetric D-π-D type efficient blue light small molecule FFA based on octylfluorene as a π bridge, where the undoped device showed efficient blue organic light-emitting device (OLED) performance with a maximum emission wavelength of 428 nm, Commission Internationale de l'Eclairage (CIE) coordinates of (0.17, 0.11) and one of the narrowest full width at half maximum (FWHM) of 35 nm. To improve the matching measure of complementary color materials for achieving white light emission, a yellow light small molecule FCzA was prepared by adjusting the conjugation degree of peripheral electron-donating groups based on the same fluorene-based π bridge with FFA. Undoped devices based on FCzA demonstrated an electroluminescence (EL) emission peak at 576 nm with CIE coordinates of (0.43, 0.49) and a relatively wide FWHM of 130 nm. Ultimately, the white OLED device was modulated with CIE coordinates located at (0.33, 0.38) via proportional regulation with a mixture of FFA and FCzA in a ratio of 10 : 3 as the light-emitting layer.

A record-high EQE of 7.65%@3300 cd m-2 achieved in non-doped near-ultraviolet OLEDs based on novel D'-D-A type bipolar fluorophores upon molecular configuration engineering.

Developing a high-performance near-ultraviolet (NUV) material and its simple non-doped device with a small efficiency roll-off and good color purity is a promising but challenging task. Here, we proposed a novel donor'-donor-acceptor (D'-D-A) type molecular strategy to largely solve the intrinsic contradictions among wide-bandgap NUV emission, fluorescence efficiency, carrier injection and transport. An efficient NUV fluorophore, 3,6-mPPICNC3, exhibiting a hybridized local and charge-transfer state, is achieved through precise molecular configuration engineering, realizing similar hole and electron mobilities at both low and high electric fields. Moreover, the planarized intramolecular charge transfer excited state and steric hindrance effect endow 3,6-mPPICNC3 with a considerable luminous efficiency and good color purity in the aggregation state. Consequently, the non-doped device emitting stable NUV light with Commission Internationale de l'Eclairage (CIE) coordinates of (0.160, 0.032) and a narrow full width at half maximum of 44 nm exhibits a state-of-the-art external quantum efficiency (EQE) of 7.67% and negligible efficiency roll-off over a luminance range from 0 to 3300 cd m-2. This is a record-high efficiency among all the reported non-doped NUV devices. Amazingly, an EQE of 7.85% and CIE coordinates of (0.161, 0.025) are achieved in the doped device. This demonstrates that the D'-D-A-type molecular structure has great potential for developing high-performance organic light-emitting materials and their optoelectronic applications.

Post-cure Heat Treatments Influence the Mechanical and Optical Properties of Acrylic and Bis-acryl Composite Resins.

To evaluate the influence of post-cure heat treatments (PCHT) on Knoop microhardness (KHN) and color change of bis-acryl composite resin (Protemp 4 - 3M ESPE, USA and PrimmaArt - FGM, Brazil) and chemically activated acrylic resins (Dencôr - Clássico, Brazil, and Duralay - Cotia, Brazil). Specimens (12×1 mm) were prepared for each material (n=10/group). Thirty minutes after curing, the specimens were subjected to PCHT for 10 minutes at 70°, 100°, or 130°C. The control group was kept at room temperature (24°C) for the same amount of time. KHN was analyzed 24 hours after PCHT (n=10). Following Commission Internationale de l'Éclairage (CIE) Delta E 2000 (CIEDE2000 [ΔE00]), color measurements were obtained at three time points: 1. after polymerization; 2. after PCHT; and 3. after 30 days of storage in water, coffee, or red wine. Data for each material were analyzed by one-way analysis of variance (ANOVA) (p<0.05). The PCHT at 130°C produced the highest KHN values. Except for the 70°C groups from Dencôr and Protemp, all PCHTs increased the initial color values (p>0.05). In general, chemically activated acrylic resins showed an increase in color stability when subjected to PCHT (p>0.05). For bis-acryl composite resin, PCHT did not influence color stability (p<0.05). Overall, the results showed that PCHT increased the tested materials' color changes and Knoop microhardness. However, except for PCHT at 130°C in Duralay, the color changes remained within acceptable values. The PCHT treatment resulted in better color stability for most of the composite resins studied.

Efficient solution-processed fluorescent OLEDs realized by removing charge trapping emission loss of BODIPY fluorochrome.

The thermally activated delayed fluorescence (TADF)-sensitized fluorescent (TSF) dye strategy has been used successfully in thermally evaporated organic light-emitting diodes (eOLEDs), but the development of solution-processed TSF-OLEDs (TSF-sOLEDs) is still very limited to date. Previously, the introduction of electronically inert shielding terminal groups for TADF sensitizer and/or fluorescent dyes was commonly used in TSF-sOLEDs, which aimed to achieve sufficient Förster energy transfer (FET) while restraining notorious Dexter energy transfer (DET) at a high doping concentration of fluorescent dyes. However, this approach has not yet enabled efficient TSF-sOLEDs owing to severe charge trapping emission (CTE) for triplet loss. In this study, by simply utilizing highly efficient boron-dipyrromethene derivatives (BODIPYs) that simultaneously feature high fluorescent quantum efficiency and narrow-band emission spectra, we developed highly efficient and super color-purity TSF-sOLEDs using a 0.1 wt% ultralow doping strategy. As confirmed, the resultant ultralow doping TSF-sOLEDs achieved sufficient FET from sensitizer to fluorochrome without noticeable CTE issues. The device achieves record maximum external quantum efficiency (EQEmax) and current efficiency (CEmax) of 21.5% and 78.8 cd A-1, respectively, and an ultrapure green emission with Commission International de l'Eclairage (CIE) coordinates of (0.28, 0.65). This study validates the new device architecture of ultralow doping TSF-sOLEDs, which paves the way for future development of high-resolution TSF-sOLED displays via a simple solution-processed manufacturing approach.

Influence of Composition and Thickness on The Color and Translucency of Glass-Ceramic Materials for Laminate Veneer Restorations: An In Vitro study

Statement of the problem: Numerous glass-ceramic materials are commercially available, yet achieving optimal esthetic results relies significantly on material composition and thickness. The selection of suitable material and thickness poses an ongoing challenge in clinical practice. Objective: This study aimed to investigate the effect of the composition and thickness of different glass-ceramic materials on the Commission Internationale de l'éclairage (CIE) L*, a*, and b* color coordinates and the translucency parameter (TP00). Materials &amp; Methods: Glass-ceramic blocks of A2 shade, with low translucency, encompassing feldspathic (FS), leucite-reinforced feldspathic (LR), and lithium-disilicate (LD) compositions, were sectioned into three thicknesses: 0.5 mm, 0.7 mm, and 1 mm (n=10). All specimens were polished with ceramic polishing rubbers. Using a spectrophotometer, the CIE L*, a*, and b* color coordinates of the specimens were measured over gray, white, and black backgrounds. The TP00 was calculated using the CIEDE2000 color difference formula. The CIE L*, a*, b*, and TP00 were analyzed using two-way ANOVA and Tukey HSD post-hoc tests (α=0.05). Results: Material, thickness, and their interaction significantly influenced the CIE L*, a*, b*, and TP00 values (P&lt;0.001). The LR group displayed the highest L* and a* values, while the LD group showed the lowest (P&lt;0.001). Conversely, the LD group exhibited the highest b* value (P&lt;0.001). Lightness was lowest in 0.5 mm-thick specimens (P&lt;0.001) and similar for 0.7 mm-thick and 1.0 mm-thick specimens (P&gt;0.05). Redness and yellowness increased with increasing thickness (P&lt;0.001). Regardless of thickness, the FS group had the highest TP00 (16.32±1.54), while the LR group had the lowest TP00 (14.31±1.67). Regardless of material, 0.5 mm-thick specimens demonstrated significantly higher TP00 (17.49±1.10) than 0.7 mm-thick (15.45±0.83) and 1.0 mm-thick (13.11±1.12) specimens. There was no significant difference between the 0.5 mm-thick FS and LD groups (P&gt;0.05) and 1.0 mm-thick LR and LD groups (P&gt;0.05). Conclusions: Even when sharing the same shade, glass ceramics may exhibit varying color and translucency properties due to their distinct chemical compositions and thicknesses.

Structure‐Based Machine Learning Enables Discovery of Mn4+‐Activated Red‐Light Fluorides for Ultrawide‐Gamut Mini‐Light‐Emitting Diodes

AbstractMn4+‐activated fluorides with a saturated red color and sharp line emission are ideal for applications in the light‐emitting diodes (LEDs) backlight for displays. However, the emissions attributed to 2E→4A2 parity and spin‐forbidden transitions limit the design and adjustments of emission wavelength and chromaticity coordinates. Herein, machine learning algorithms are used to build a wavelength‐prediction model for Mn4+‐activated fluorides. The model precisely identifies the key structural features that affect wavelengths and discovers target materials. The predicted candidate Cs2NaAlF6:Mn4+ (CNAF) with a long‐wavelength zero‐phonon‐line emission at 628 nm exhibits a redshift in comparison with other reported Mn4+‐activated fluorides and commercial K2SiF6:Mn4+, but maintains narrow spectral emission with full‐width half maximum (FWHM) of 11.2 nm. The redshift and narrow spectra result in a color purity of 99.7% and Commission Internationale de L'Eclairage (CIE) chromaticity coordinate of (0.7032,0.2967) that is close to the pure red‐light point of Recommendation BT. 2020 (Rec. 2020). Moreover, CNAF is prepared as a transparent red‐light film, and the device fabricated using the blue‐light mini‐LEDs, green quantum‐dot film, and CNAF film exhibits a wide color‐gamut of 121.5% National Television Standards Committee (NTSC) or 90.6% Rec. 2020, suggesting that CNAF has potential for wide‐color‐gamut displays.

Synthesis and characterization of thermally stable red light-emitting Eu3+ activated Li7La3Zr2O12 phosphors for solid-state lighting applications

To enhance the photoluminescence property of Li7La3Zr2O12 (LLZO), Eu was doped using a solid-state synthesis technique. X-ray diffraction and Raman spectroscopy analysis were used to examine the crystal structure of the synthesized phosphors. The optical band gap values of pristine and Eu3+ doped LLZO phosphor investigated using ultraviolet-visible (UV-Vis) spectroscopy were measured to be 2.74 and 2.97 eV, respectively. The wavelengths of pure and doped LLZO samples were measured and fitted by the Commission Internationale de l’Eclairage (CIE) chromatic coordinate graph. These samples were found to emit blue emission at 354 nm (pure LLZO) and red emission at 464 nm (doped phosphor), which correspond to the 5D0 to 7Fj (j = 0, 1, 2, and 3) transition. The purity of the color and correlated color temperature with respect to the 0.9 M.W% Eu3+ doped (activated) LLZO sample were estimated to be 80% and 1719K, respectively. The indication of its maximum emissive capability at this rate was found suitable for aesthetic lighting applications.

Synthesis, structure and optoelectronic properties of iridium(III) complexes bearing a four-membered Ir-N-C[sbnd]N chelate structure

Herein four novel iridium(III) complexes (tfpmd)2Ir(dpppy) (Ir1a, tfpmd = 2-(4-(trifluoromethyl) phenyl) pyrimidine, dpppy = P,P-diphenyl-N-(pyridin-2-yl)phosphinic amide), (tfpmd)2Ir(dppq) (Ir1b, dppq = P,P-diphenyl-N-(quinolin-2-yl)phosphinic amide), (tfpqz)2Ir(dpppy) (Ir2a, tfpzq = 4-(4-(trifluoromethyl) phenyl) quinazoline) and (tfpqz)2Ir(dppq) (Ir2b) were synthetized, and their structures, opto-physical, and electro-chemical properties were investigated in detail. The crystal structure shows that these complexes exhibit pseudo-octahedral geometry around iridium atom coordinated by C, N atoms from cyclometalated and ancillary ligands. Interestingly, two coordinated nitrogen atoms from the ancillary ligand form an unusual quaternary ring with the central iridium ion. Ir1a and Ir1b emit pure-green light with Commission Internationale de L'Eclairage (CIE) color coordinates of (0.25, 0.67) and (0.22, 0.67), respectively, in CH2Cl2 solution. With the increase of the degree of conjugation of the cyclometalated ligand from tfpmd to tfpqz, the luminescence of complexes Ir2a and Ir2b is greatly red-shifted, and pure-red emission with CIE coordinates of (0.66, 0.34) and (0.66, 0.34), respectively, is obtained. The photophysical behaviors were reasonably explained by quantum chemical calculations. The calculation results shows that their emission is ascribed to the mixed 3MLCT (metal-ligand charge transfer, dπ(Ir)→π*(cyclometalated ligand)) and 3LLCT (ligand-ligand charge transfer, π(ancillary ligand)→π*(cyclometalated ligand)) states. Owing to their good thermal and electrochemical stabilities, organic light emitting diode (OLED) devices with dual-emitting layer structure and a space interlayer were fabricated and exhibited high electroluminescent properties and mild efficiency roll-off (14%-21%).

Highly efficient deep blue electroluminescent material with high and towards balanced carrier transmission performance based on hybrid local and charge-transfer (HLCT) excited state

Deep blue electroluminescent materials play a decisive role in organic light-emitting diodes (OLEDs). Herein, three novel deep blue molecules based on hybridized local and charge-transfer (HLCT) excited state were reported, namely CZFPY, CZFPI and TPAFPI. Single-crystal analysis of TPAFPI shows abundant intermolecular interactions, which restricts molecular rotation and suppresses structural vibrations, promotes TPAFPI achieved a high photoluminescence quantum yield (PLQY) up to 72 % in solid state. More importantly, these abundant intermolecular interactions significantly increase its carrier mobilities, with hole and electron mobilities as high as 1.2 × 10−5 cm2 V−1 s−1 and 5.4 × 10−6 cm2 V−1 s−1, respectively. Consequently, the non-doped OLED based on TPAFPI achieved excellent device performance, the maximum current efficiency (CEmax) is 12.4 cd/A, the maximum power efficiency (PEmax) is 14.0 lm W−1, the maximum external quantum efficiency (EQEmax) is 7.2 % with high device stability, the efficiency roll-off is only 4.7 % at 1000 cd m−2. What is more, the doped device of TPAFPI exhibits a higher EQEmax of 10.1 % with a higher color purity, the Commission International de L’Eclairage (CIE) coordinate is (0.15, 0.06), matching the National Television Standards Committee (NTSC) standard. The comprehensive performance of TPAFPI-based doped device is at the highest level in the field of deep blue OLEDs (0.06 ≤ CIEy ≤ 0.09).

Triphenylamine-phenylimidazole based hybridized local and charge-transfer molecular as blue-green/ white light emission emitter for light-emitting diode application

In this work, a new triphenylamine-phenylimidazole derivative named (E)-N,N-diphenyl-4-(2-(4'-(1-phenyl-1H-benzo[d]imidazole-2-yl)-[1,1′-biphenyl]-4-yl)vinyl)aniline (DPAvlBPI) with hybridized local and charge-transfer (HLCT) characteristics was successfully developed. The undoped organic light-emitting diode (OLED) based on DPAvlBPI (XF-OLED) is prepared with a maximum external quantum efficiency (EQE) of 1.23 %, and the exciton utilization efficiency (EUE) can reach 41 %. The Commission Internationale de L'Eclairage (CIE) color coordinate of XF-OLED is (0.1925, 0.3975), indicating that the device is in the blue-green light region. Since the photoluminescence quantum efficiency (PLQY) of DPAvlBPI in neat film is only 0.12, the maximum brightness of the device is 545 cd m−2. However, by dispersing DPAvlBPI in silica gel at a low concentration, the PLQY can approach 1. Therefore, the DPAvlBPI-based organic/inorganic hybrid LED XF-HBLED is prepared, and the device can achieve a luminous efficacy of 18.64 lm/W and EQE of 9.98 % at an operating current of 64.90 mA. To broaden the application scope of DPAvlBPI, a “Halochromism” white light emission system based on DPAvlBPI has been prepared, and the solution type (XF-SWLED) and solid-state(XF-W2) white light emission device based on this system have been successfully realized. The luminous efficacy of XF-W2 with a CIE coordinate of (0.3205, 0.4363) can reach 14.92 lm/W with an EQE of 8.23 % under the operating current of 64.90 mA. This provides a reference for expanding the multifunctional/multi-device applications of HLCT molecules.

Efficient deep blue fluorescent emitters based on bipolar phenanthroimidazole-carbazole hybrid for non-doped electroluminescent device with small CIEy

In this work, four bipolar deep-blue emitting materials of 2-(4-(9H-carbazol-9-yl)phenyl)-1-(4-methylphenyl)-1H-phenanthro[9,10-d]imidazole (MePPIM-Cz), 2-(4-(9H-carbazol-9-yl)phenyl)-1-(4-chlorophenyl)-1H-phenanthro [9,10-d]imidazole (ClPPIM-Cz), 2-(4-(9H-carbazol-9-yl)phenyl)-1-(4-tert-butyl phenyl)-1H-phenanthro[9,10-d]imidazole (BuPPIM-Cz) and 2-(4-(9H-carbazol-9-yl) phenyl)-1-(4-(trifluoromethyl)phenyl)-1H-phenanthro[9,10-d]imidazole (TFMPPIM-Cz) based on phenanthroimidazole and carbazole group have been designed and synthesized by introducing different electron active substitutions into the N1 position of phenanthroimidazole. The thermal, photophysical, electrochemical and computational properties of four compounds were investigated. All compounds exhibited the deep blue emission and good thermal stability with glass transition temperature (Tg) in range of 126°C–137 °C. Single carrier devices were also fabricated and demonstrated that the four compounds have bipolar transporting properties. The non-doped organic light emitting diodes (OLEDs) based on MePPIM-Cz, ClPPIM-Cz, BuPPIM-Cz and TFMPPIM-Cz showed deep blue emission with the Commission Internationale de L'Eclairage (CIE) coordinates of (0.16, 0.07), (0.16, 0.06), (0.16, 0.05) and (0.16, 0.10) and the maximum external quantum efficiencies (EQEmax) of 2.67%, 2.24%, 1.81% and 1.09%, respectively. The CIE coordinates of MePPIM-Cz, ClPPIM-Cz and BuPPIM-Cz is extremely close to the National Television System Committee (NTSC) standard blue CIE of (0.14, 0.08), which is very significant for high color purity full-color display.

Controlling of precursor micelle size by ternary co-spacer cations for efficient pure red quasi-2D PeLEDs with recommendation 2020 color coordinates

Quasi-two-dimensional (quasi-2D) perovskites have emerged as one of the most promising luminescent materials owing to their outstanding optoelectronic properties and facile solution processability. However, high-performance pure red quasi-2D perovskite light-emitting diodes (PeLEDs) still remain a great challenge due to wide phase distribution and inefficient quantum well energy transfer. Here, we develop a ternary co-spacer cations system to vary the micelle size of the precursor solution and to modulate the phase distribution in film using phenylbutyl-ammonium (PBA+) as the third spacer cation, which has stronger binding energy with lead-halide octahedron. By virtue of its additional defect passivation effect, the resulting device displays a champion maximum external quantum efficiency (EQE) of 15.7 % with an electroluminescent peak at 631 nm and Commission Internationale de l’Éclairage (CIE) coordinates of (0.709, 0.290) as well as excellent spectral stability. This work provides useful guidance for perovskite phase modulation and the development of highly efficient pure-red PeLEDs.

Synthesis and study of luminescence properties of a deep red-emitting phosphor K2 LiAlF6 :Mn4+ for plant cultivation.

Light is the most important component in plant growth and development. This study synthesised a novel Mn4+ -doped K2 LiAlF6 red-emitting phosphor using the coprecipitation method. We observed that on addition of dopant Mn4+ ions to the host K2 LiAlF6 , its phase changed from rhombohedral to cubic due to the change in the lattice position of the atoms. When the atoms are excited at 468 nm, the K2 LiAlF6 :Mn4+ phosphor exhibited a red emission band ranging from 630 to 700 nm, centred at 638 nm, which matched well with the absorption spectra of phytochrome PR. The critical quenching content of Mn4+ ions was ~3mol%. The critical distance between Mn4+ ions was determined to be 19.724 Å, and non-radiative energy transfer among the nearest-neighbour Mn4+ ions was the mechanism used for the concentration quenching effect. The Commission International de l'Eclairage (CIE) chromaticity coordinates of the K2 LiAlF6 :0.03 Mn4+ sample were (x = 0.7162, y = 0.2837). The luminescence mean decay time was calculated to be 8.29 ms. These results demonstrated the promising prospect of K2 LiAlF6 :Mn4+ as a red-emitting phosphor for application in red light-emitting diodes for plant cultivation.

Influence of phase composition and crystal structure on the luminescent properties of calcium aluminates (CaAl2O4, CaAl4O7, CaAl12O19) activated by Eu3+ ions

Calcium monoaluminate, dialuminate, and hexaaluminate and luminophores based on them activated by europium (III) ions were obtained by the citrate-nitrate gel method. X-ray diffraction (XRD) and Full-Profile Rietveld refinement were used to establish the parameters of single-phase systems, to analyze the structure of the investigated compounds, and to determine the most probable sites of calcium substitution by the activator. The interpretation of the emission spectra has shown that europium occupies two crystallographic positions in calcium monoaluminate, while in dialuminate and hexaaluminate europium has only one crystallographic environment. Phosphor emission bands lie in the range from 580 to 720 nm, but the splitting of bands and their intensity are different. This is due to the different symmetry of the europium environment in the aluminate matrixes. This makes it possible to obtain phosphors of different hues of luminescence from the same starting materials, which is confirmed by the Commission Internationale de L'Eclairage (CIE) chromatic coordinate diagram.

Effect of Temporary Cement on the Color of Temporary Crowns Made by Conventional Pressing Methods and Substractive CAM/CAD Technologies

The color stability of temporary restoration is crucial, especially in sensitive areas in terms of aesthetics. This research aimed to determine the effect of temporary cement on the color of temporary crowns made by conventional pressing methods (indirect) and CAM/CAD technologies using milling machines and 3D printers. This study was carried out in a laboratory, utilizing A2 color in all manufacturing methods. The color of the restorations was measured by a spectrophotometer after cementation with semi-permanent resin cement. Subsequently, color changes of the samples (ranging from 0 to 100) were calculated using the Commission International de l'Eclairage (CIE) Lab system. Data analysis was based on descriptive statistics methods and statistical tests, including one-way analysis of variance (ANOVA) and Tukey's post hoc test. According to the results of ANOVA, there was a significant difference between the three groups in terms of the 'a' and 'b' indexes (P&lt;0.001). However, regarding the 'l' index, no significant difference was observed among the three groups (P=0.250). Also, based on Tukey's post hoc test, a significant relationship was seen between the first and second pairs in the 3D printer group, and between the first and third pairs in the milling group (P&lt;0.001). However, no significant difference was observed in the conventional pressing group. The results showed that the 3D printing method exhibited the highest amount of color change among the three methods, while the milling method demonstrated the lowest amount of change.

Novel approach to enhance the optical and electrical properties of polymer electrolytes using phenol red dye

AbstractThis article comprehensively analyzes how phenol red dye affects the optical, structural, and electrical properties of sodium bromide‐doped polymer electrolyte films based on sodium carboxymethyl cellulose. Conventional solution casting technique has been employed to prepare the electrolytes. The optical analysis reveals that incorporating the phenol red dye improves the optical properties. Fourier transform infrared spectroscopy is used to study the kind of complexation between the polymer and dopants. Scanning electron microscope micrographs of the electrolytes indicate the acquisition of free volume on the surface of the polymer matrix. The electrical properties are studied using impedance analyzer, which shows that the ionic conductivity increases when the dye is incorporated. The electrolyte system incorporated with 0.25 wt% of the dye exhibits the highest conductivity among the other systems. Photoluminescence investigation demonstrates that doping increases the intensity of the photoluminescence emission as it minimizes the free volume size. Commission Internationale de l'Eclairage (CIE) chromatograph studies indicate that the doped samples emit a yellow color with a color purity of 97%. All in all, the findings imply that adding dye to the polymer matrix increases the electrical and visual characteristics of the polymer electrolyte.Highlights Phenol red dye improves the optical properties of sodium carboxymethyl cellulose‐based polymer electrolytes. Scanning electron microscope micrographs reveal the creation of free volume on the surface of electrolyte films. Analysis of electrical properties shows a slight increase in ionic conductivity with dye incorporation. Photoluminescence intensity increases with dye due to reduced free volume size. Doped samples emit 97% purity yellow enhancing electrical and optical properties.

Rational Medium-Range Charge Transfer Strategy Toward Highly Efficient Violet-Blue Organic Light-Emitting Diodes with Narrowed Emission.

The spectral narrowing engineering of pure-organic emitters attracts great research interests in realizing high color purity. Here, the adjusted medium-range charge transfer (MCT) strategy of TIC-BO with rigid planar structure by fusing two typical UV-emitting multiple resonance (MR) fragments via the ingenious double-halide cyclized coupling reaction is reported. The resulting TIC-BO with MCT nature shows efficient violet-blue emission in dilute toluene and evaporated host-guest films, and desirably narrowed spectra are achieved by the suppression of structural relaxation and the shortened charge transfer states. The single-doped device with TIC-BO as emitter shows narrowed violet-blue electroluminescence peaked at 428nm with full-width at half-maximum of 43nm (0.28eV), and the Commission Internationale de l'Éclairage coordinates of (0.160, 0.050). A maximum external quantum efficiency (EQEmax ) of 20.50% is achieved, which is among the best results of the corresponding violet-blue emitting region. Further introduction of a stronger electron-donating carbazole group makes TIC-BNO exhibit red-shifted sky-blue emission with MR-dominant properties, and good device performance is received with EQEmax of 34.58%. The outstanding performances of TIC-BO successfully demonstrate the significance and prospect of the proposed molecular design strategy.