CIE Coordinates Research Articles

In situ coupling of carbon dots with zeolitic imidazolate frameworks enabling highly red emission in solid state

In this work, an extraordinary solid red emissive phosphor was prepared based on red-emitting carbon dots (R-CDs). The synthesis was conducted under an in-situ strategy, with assistance of zeolitic imidazolate frameworks. The obtained phosphor possesses a stronger red emission located at 630 nm in solid state, with CIE coordinate of (0.63, 0.35) and quantum yield of ∼ 45 %. As a consequence, not only aggregation-induced fluorescence quenching of R-CDs is avoided in solid state, but also an enhanced emission with high quantum yield is presented. Fluorescence properties were further explored in detail. The emission is found to be responsive to temperature and applied pressure. Based on the excellent emissive performance, the material has great potentials in anti-counterfeiting, latent fingerprint imaging, and temperature/pressure-sensing. This work provides a facile and promising way of preparing solid carbon-based phosphors for special applications.

Boron-, sulfur- and nitrogen-doped decacyclic multiple resonance emitters for narrowband deep blue electroluminescence

Two boron-, sulfur- and nitrogen-doped polycyclic aromatic hydrocarbon (PAH) multiple resonance (MR) emitters, namely mDBNS and mDBNStBu, are developed by introducing two pairs of boron (B) and sulfur (S) atoms at meta-positions of central benzene and one carbazole moiety in decacyclic aromatic skeletons. The resultant emitters exhibit efficient deep blue narrowband emission at 451–457 nm with full width at half maximum (FWHM) of 18–22 nm in toluene, together with PLQY of 70%–76% and reverse intersystem crossing rate (kRISC) of 1.1–1.2 × 105 s−1. Solution-processed organic light-emitting diodes (OLEDs) employing mDBNStBu as emitters exhibit deep blue electroluminescence at 462 nm with CIE coordinates of (0.13, 0.12), together with a maximum external quantum efficiency (EQEmax) of 10.4%.

Rigidity‐Enhanced Narrowband Iridium(III) Complexes with Finely‐Optimized Emission Spectra for Efficient Pure‐Red Electroluminescence

AbstractAttaining phosphorescent materials with narrowband emission is crucial for advancing wide‐color‐gamut organic light‐emitting diode (OLED). Herein, a rigid modification strategy is introduced for iridium(III) complexes to achieve the narrowband red emission with negligible 0–1 peak. By introducing the rigid indolo[3,2,1‐jk]carbazole (ICz) into the cyclometalated ligand, Ir(III) complexes, ICziq‐Ir and ICzqz‐Ir, exhibit pure red phosphorescence with emission peaks at 608 and 613 nm and full widths at half‐maximum (FWHMs) of 37 and 38 nm (0.12 and 0.13 eV) in toluene, respectively. Furthermore, the specific site modification of ICzqz‐Ir greatly suppresses the high‐frequency vibration of the structure, resulting in the narrowband photoluminescent spectrum close to the Gaussian distribution with superior color purity. The OLEDs utilizing ICziq‐Ir and ICzqz‐Ir demonstrate maximum external quantum efficiencies of 21.4 and 17.8% as well as mild efficiency roll‐off. Remarkably, the electroluminescence spectra exhibit similar narrowband red emission with FWHMs of 37 and 43 nm and CIE coordinates of (0.65, 0.35) and (0.66, 0.34), attesting to the excellent color purity of the phosphorescent OLEDs.

Precise Modulation of Circularly Polarized Luminescence via Polymer Chiral Co‐assembly and Contactless Dynamic Chiral Communication

AbstractCircularly polarized luminescence (CPL) plays a pivotal role in cutting‐edge display and information technologies. Currently achieving precise color control and dynamic signal regulation in CPL still remains challenging due to the elusory relationship between fluorescence and chirality. Inspired by the natural mechanisms governing color formation and chiral interaction, we proposed an addition‐subtraction principle theory to address this issue. Three fluorene‐based polymers synthesized by Suzuki polycondensation with different electron‐deficient monomers exhibit similar structures and UV/Vis absorption, but distinct fluorescence emissions due to intramolecular charge transfer. Based on this, precise‐color CPL‐active films are obtained through quantitative supramolecular co‐assembly directed by addition principle. Particularly, an ideal white‐emitting CPL film (CIE coordinates: (0.33, 0.33)) is facilely fabricated with a high quantum yield of 80.8 % and a dissymmetry factor (glum) of 1.4×10−2. Structural analysis reveals that the ordered stacking orientation favors higher glum. Furthermore, to address the dynamically regulated challenge, the comparable subtraction principle is proposed, involving a contactless chiral communication between excited and ground states. The representative system consisting of as‐prepared fluorene‐based polymers and chirality‐selective absorption azobenzene (Azo)‐containing polymers is constructed, achieving CPL weakening, reversal, and enhancement. Finally, a switchable quick response code is realized based on trans‐cis isomerization of Azo moiety.

Precise Modulation of Circularly Polarized Luminescence via Polymer Chiral Co-assembly and Contactless Dynamic Chiral Communication.

Circularly polarized luminescence (CPL) plays a pivotal role in cutting-edge display and information technologies. Currently achieving precise color control and dynamic signal regulation in CPL still remains challenging due to the elusory relationship between fluorescence and chirality. Inspired by the natural mechanisms governing color formation and chiral interaction, we proposed an addition-subtraction principle theory to address this issue. Three fluorene-based polymers synthesized by Suzuki polycondensation with different electron-deficient monomers exhibit similar structures and UV/Vis absorption, but distinct fluorescence emissions due to intramolecular charge transfer. Based on this, precise-color CPL-active films are obtained through quantitative supramolecular co-assembly directed by addition principle. Particularly, an ideal white-emitting CPL film (CIE coordinates: (0.33, 0.33)) is facilely fabricated with a high quantum yield of 80.8 % and a dissymmetry factor (glum) of 1.4×10-2. Structural analysis reveals that the ordered stacking orientation favors higher glum. Furthermore, to address the dynamically regulated challenge, the comparable subtraction principle is proposed, involving a contactless chiral communication between excited and ground states. The representative system consisting of as-prepared fluorene-based polymers and chirality-selective absorption azobenzene (Azo)-containing polymers is constructed, achieving CPL weakening, reversal, and enhancement. Finally, a switchable quick response code is realized based on trans-cis isomerization of Azo moiety.

One-step microwave synthesis of high-efficiency solid-state luminescent carbon dots with aggregation-induced emission

Carbon dots (CDs) are biophilic quantum dots with excellent luminescent properties, however, the aggregation-caused quenching (ACQ) effect is a serious limitation for their application in solid-state devices. In this manuscript, a solid-state luminescent blue CDs (B-CDs) with a high fluorescence quantum yield of 52% was prepared by a microwave-assisted method. The B-CDs showed weak fluorescence and with a photoluminescence fluorescence quantum yield (PLQY) of only 0.63% in aqueous solution, but exhibited an aggregation-induced emission in the solid state. The AIE phenomenon of B-CDs was shown to result from the inhibition of surface chromophore motion during aggregation by characterizing the PL intensity under different ratios of DCM (poor solvent). Furthermore, the fluorescence kinetic mechanism associated with the B-CDs was investigated by the time-resolved PL. Finally, a blue LED with CIE coordinates of (0.15, 18) was fabricated using B-CDs as the phosphor, showing a promising potential application in solid-state optoelectronic devices.

Fluorescent Carbonized Polymer Dots Derived from o-phenylenediamine and its Photonic Application.

Optimizing the optoelectronic characteristics of low-dimensional carbon dots (CDs) through surface modifications and doping has proven instrumental in tailoring them for diverse applications. This study explores a facile and economical hydrothermal synthesis method for generating Carbonized Polymer Dots using o-phenylenediamine at different temperatures. The resulting materials exhibit structural and morphological variations linked to the synthesis temperature. A transition from carbon dots (CDs) embedded in reduced graphene oxide (rGO)-like sheet structures at low temperatures to the core-shell structure at the highest temperature is observed in HR-TEM, implying the formation of CPDs. X-ray photoelectron spectroscopy (XPS) corroborates these findings, showing an augmented degree of graphitization in alignment with HR-TEM results. The photoluminescence spectra of CPDs synthesized at the lowest temperature exhibit multiple emission peaks, resulting in a yellowish-orange color. Utilizing these CPDs to fabricate light-emitting diodes (LEDs) produces a vivid bright-green emission with CIE coordinates (0.378, 0.522). Moreover, the CPDs demonstrate solvatochromism across diverse solvents of varying polarity, covering the entire visible spectrum. This intriguing solvatochromic effect positions the CPDs as promising materials for polarity probing applications.

Synthesis and Spectroscopic Investigations of Sm3+ Activated ZrO2 and Na2ZrO3 as Warm Light Phosphors.

In this work, we investigate how the structural and optical characteristics of ZrO2 and Na2ZrO3 are influenced by Sm3+ ion doping. Urea-assisted combustion approach is employed by varying the molar concentration of Sm3+ ions in both the host lattices. XRD pattern revealed the monoclinic crystal system for both samples. XPS investigation has been examined to acquire the chemical information of the samples. FESEM is used to identify the morphology of the samples. The optimum molar concentrations of Sm3+ doped ZrO2 and Na2ZrO3 phosphors, as per photoluminescence (PL) findings, are 1.5mol% and 2mol%, respectively. CIE coordinates of ZrO2:Sm3+ and Na2ZrO3:Sm3+ are found to be (x = 0.59, y = 0.41) and (x = 0.61, y = 0.39) that corresponds to the amber region of color gamut. The optical bandgap for the synthesized samples is estimated using the UV-Vis diffuse reflectance spectra and the obtained values for the optimal concentration of dopant (Sm3+) in the ZrO2 and Na2ZrO3 samples are 4.61 and 4.94eV, respectively. The findings of the study reveal that the synthesized phosphors may be utilized as warm light phosphors and be a promising candidate for amber light-emitting diodes (LEDs).

Tuning the Liquid Crystallinity and Electroluminescence via Sulfonation of S-Annulated Perylene Tetraester.

This study presents a comparative analysis of S-annulated perylene tetraester (PTE-S) and its sulfone (PTE-SO2) analogue. This sulfone modification reduced melting point and stabilized a room temperature columnar rectangular (Colr) phase in contrast to its parent PTE-S which showed a crystalline behaviour at room temperature. This molecular design also leads to red-shifted absorbance and emission in comparison to PTE-S, along with a tuning of photoluminescence from sky blue to green, achieving an impressive quantum yield of 85 %. OLED devices fabricated using PTE-SO2 as emitter material at concentrations of 0.2, 0.5, and 1 wt.% in CBP as host material. A maximum external quantum efficiency (EQE) of 2.9 % was observed with the 0.5 wt.% PTE-SO2 in CBP with CIE coordinates of (0.45, 0.35), accompanied by an orange luminance of 848 cd/m2. Notably, a device with a 0.5 wt% doping concentration of PTE-S demonstrates an EQE of 3.5 %, and cyan luminance of 2,598 cd/m2.

Highly emissive 0D Tin(II) hybrid for white LED

The pursuit of environmentally friendly and highly luminescent phosphors for down-conversion white light-emitting diodes (WLEDs) remains a significant focus of research. Here, we present a novel zero-dimensional Sn(II) hybrid exhibiting vibrant orange emission peaking at 598 nm and an outstanding photoluminescence quantum yield of 69%. This hybrid, designated as (C7H8N3)4SnBr6, was synthesized via the reaction of 2-aminobenzimidazole with SnBr2, revealing distinctive self-trapped exciton emission characteristics, contributing to its broad-band emission and prolonged lifetime. Subsequently, a down-conversion WLED was constructed by integrating the Sn(II) hybrid with a green phosphor ((Sr, Ba)2SiO4:Eu2+) and a blue phosphor (BaMgAl10O17:Eu2+), resulting in CIE coordinates of (0.313, 0.331), a correlated color temperature of 6466 K, and an impressive color rendering index of 90.6. This work enriches the family of lead-free hybrid phosphors, showcasing their potential for highly efficient white LED applications.

Sr0.99Zr(PO4)2:0.01Eu3+ ceramic glass for photoluminescence applications

This paper reports the first-time synthesis of Sr0.99Zr(PO4)2:0.01Eu3+ nanophosphor via solution combustion method using glycine as fuel at a fuel-to-oxidizer ratio of 1:1. The PXRD pattern confirmed the formation of the desired phase, while the Scherrer calculation revealed an average particle size of approximately 60 nm. Scanning electron microscopy (SEM) further corroborated the particle size, estimating it around 75 nm. The material exhibited a characteristic mesoporous structure, a hallmark of the solution combustion synthesis technique. Photoluminescence (PL) spectroscopy revealed two intense emission peaks at 590 nm and 615 nm, attributed to Eu3+ ions, suggesting potential applications in LED technology. CIE coordinates indicated emission close to the white region defined by the NTSC standard

High efficiency white emission in Na3Ba2Ca(PO4)3:Eu2+, Mn2+ phosphors for urban ecological lighting

The white-light-emitting devices (WLEDs) for urban ecological lighting remain the challenge. The current urban lighting system destroys the growth habits of plants and leads to inhibition of plant growth, reduced branching, smaller leaf area and reduced total dry weight due to excessive blue light. In this work, a series of blue-green and red dual-emission Na3Ba2Ca(PO4)3:Eu2+, Mn2+ phosphors have been successfully synthesized by the high-temperature solid-state reaction method. The crystal structure, the occupancy of the dopant ions and the luminescence characteristics were carefully investigated. The excitation and emission spectra as well as the decay lifetime confirm the effective energy transfer from Eu2+ to Mn2+, which leads to a tunable luminescence with greatly reduced blue emission. Especially, the optimal Na3Ba2Ca(PO4)3:0.02Eu2+, 0.11Mn2+ phosphor demonstrates a high internal quantum yield of 99.7%. At 150 °C, the luminescence intensity of Na3Ba2Ca(PO4)3:0.02Eu2+, 0.11Mn2+ can maintain 64.5% of room temperature intensity. In addition, the WLED device fabricated with Na3Ba2Ca(PO4)3:Eu2+, Mn2+ phosphor shows white light emission with CIE coordinates of (0.3800, 0.3852), rendering index (Ra) of 65.4 and correlated color temperature (CCT) of 3640 K. These results confirm that the Na3Ba2Ca(PO4)3:Eu2+, Mn2+ phosphor can be applied as a white light source in the urban ecological field.

Interrupting the long-range energy migration among Eu3+ by the introduction of unequivalent [NaO8] units to achieve both high quenching concentration and quantum yield in NaY2Ga2InGe2O12

In the pursuit of optimizing white light-emitting diodes (WLEDs), Eu3+-doped phosphors have emerged as a key component in strategies that combine ultraviolet (UV) LED chips with red, green, and blue (RGB) tricolor phosphors. However, their application has been notably constrained by concentration quenching and thermal quenching. To address this challenge, we have developed a series of novel red phosphors, NaY2-xGa2InGe2O12:xEu3+. The powder X-ray diffraction (XRD) indicates that the NaY2Ga2InGe2O12(NYGIG) belongs to the garnet family. The [NaO8] unit replaces one-third of the eight-coordinated sites of garnet and leaves the other two-thirds for the [YO8], which helps to prevent long-range energy migration among Eu3+ especially when the eight-coordinated sites were highly substituted. Such a structure feature allowed the NaY2-xGa2InGe2O12:xEu3+ phosphor to achieve an optimal quantum yield of 95.6% at an extremely high Eu3+ doping x value up to 1.2. Moreover, further studies on the temperature-dependent luminescence spectra confirm that an anomalous thermal quenching phenomenon will occur when the NaY2-xGa2InGe2O12:1.2Eu3+ phosphor is properly excited. In application, the combination of the red-emitting NaY2-xGa2InGe2O12:1.2Eu3+, blue-emitting BaMgAl10O17:Eu2+, and green-emitting Zn2SiO4:Mn2+ phosphors can realize high color rendering (CRI∼93) white light with the with CIE coordinates of (0.353,0.350), indicating that the NYGIG:Eu3+ phosphor own a promising potential for WLEDs.

Dual fluorescence induced thermally activated delayed fluorescence materials based on 2,4-Diphenylthieno[3,2-d]pyrimidine with an efficient single-molecular white electroluminescence

Dual fluorescence compounds exhibit a wide emission spectrum in visible-light range and show huge application prospect in white-light OLED (WOLED). However, few of them can realize the trade-off between high color purity of white-light emission and high emission efficiency. In this work, using sulfur atom-fused electron acceptor (A) unit 2,4-diphenylthieno[3,2-d]pyrimidine (TP) and planar electron donor (D) unit phenothiazine (PTZ), a series of novel dual fluorescence compounds with simple twisting D-A configuration were designed and synthesized, denoted as PTZ-2TP, PTZ-4TP and DPTZ-TP, respectively. Simultaneous dual fluorescence emission could be realized both solution and film state of the current system via optimizing polarization environment and doped concentration, which are attributed to the characteristic quasi-axial (QA) and quasi-equal (QE) conformations. Subsequently, these compounds were successfully applied in WOLED with high efficiency. DPTZ-TP as emitter endows the WOLED with the best device performance with greenish-white light emission, CIE coordinates of (0.33, 0.44) and high EQEmax of 11.87%, which is the highest records of such single compound systems.

Combustion synthesis, structural and photoluminescent investigations of Eu3+ activated crystalline Ba2BiV3O11 nanomaterials for multifunctional applications

Nanocrystalline Ba2BiV3O11 phosphor activated with lanthanide ion (Eu3+) has been successfully developed via a solution combustion approach. Various characterization techniques were implemented to explore the crystal structure, morphological behavior, photoluminescence, and chromatic aspects of Eu3+: Ba2BiV3O11 nanophosphors. Rietveld refinement was exercised to attain the phase purity and various crystallographic parameters. Transmission Electron Microscopy (TEM) technique was employed to analyze the crystallite size of the developed nanocrystals which is also in agreement with the size calculated from Scherrer formalization and W-H (Williamson-Hall) plot. Morphological behavior was studied with the help of Scanning Electron Microscopy (SEM) measurements. The most intense peak centered at 622 nm (5D0 → 7F2) in emission spectra was noted for Eu3+: Ba2BiV3O11 nanophosphors under 348 nm excitation. Kubelka-Munk function computed the Egap for the host along with the optimized sample and the outcomes evolved as 3.47 eV and 3.41 eV, respectively. Auzel’s model was executed to attain the radiative lifetime (1.3467 ms) for 5D0 electronic state. The CIE coordinates (x = 0.5990, y = 0.4003), CCT values (1710 K), quantum efficiency (87 %), and emission of bright red light indicate the promising behavior of Ba2Bi0.9Eu0.1V3O11 nanophosphor to use in the imaging applications, wLEDs, temperature sensing, and solid-state lighting (SSLs) appliances.

[formula omitted] mediated green synthesis of Ga2O3-ZnO nanocomposite for display technology and latent finger print detection

For the first time, Ga2O3-ZnO (GaZn) Nanocomposites (NCs) were synthesized by Green’s method using Aeglemarmelos fruit extract as a reducing agent via solution combustion method. Bragg’s reflection clearly confirms the formation of monoclinic and hexagonal Wurtzite structure of Ga2O3 and ZnO nanoparticles respectively. The crystallite size calculated by Scherrer’s method was found to be 21 nm. The agglomerated, irregular shape and sized NCs are observed in surface morphology. The direct band gap energy was calculated using Wood and Tauc’s plot which was found to be 3.1 eV. Photoluminescence emission spectra of GaZn NCs recorded at 350 nm consist of broad emission spectra with different sharp emission peaks overlapped over the broad spectra. CIE and CCT coordinates confirm the intense blue emission of synthesized NCs. Further, the synthesized NCs are analyzed for latent fingerprint (LPF) in the field of forensic application.

Achieving efficient and stable blue organic light-emitting diodes via suppressing triplet–polaron annihilation processes

It is still challenging to achieve blue OLEDs with sufficient color purity, lifetime and efficiency for applications. Thermally activated delayed fluorescence (TADF) materials become the most promising. However, the internal mechanism of the efficiency roll-off and long-term stability degradation still needs deep research. In this work, the energy transfer and exciton quenching processes in TADF-based blue OLEDs were analyzed under steady-state conditions and their relative contributions to efficiency roll-off were quantified. Furthermore, the degradation mechanism in the TADF-based blue OLEDs was investigated both theoretically and experimentally by a comprehensive exciton quenching model. It was demonstrated that suppressing the triplet–polaron annihilation processes and reducing the accumulation of triplet excitons through reasonable energy transfer can decrease the effect of exciton quenching, thereby significantly reduce the efficiency roll-off and improve device lifetime. It can be seen that the external quantum efficiency (EQE) of the resulting blue OLEDs was enhanced to 30.3 % with CIE coordinates of (0.16, 0.25) and kept 20.9 % at the luminance of 1000 cd/m2. More importantly, the device lifetime was also significantly enhanced, which is over three times longer than that of the unoptimized devices due to the suppress of triplet-polaron annihilation and triplet accumulation.

Strong donor-acceptor interaction of difluoroboron β-diketonates with polyvinylcarbazole: Deeply red-shifted emission of charge-transfer complexes and exciplexes

Donor-acceptor systems exhibiting exciplex luminescence attract much attention due to the wide prospects for their application in the field of OLEDs, nonlinear optics and lasers. Difluoroboron β-diketonates (BF2bdks) are a well-known class of organic dyes, which are able to form effective exciplex fluorescence, but this process has not received due attention for practical application. Strong donor-acceptor interaction in polyvinylcarbazole (donor) and BF2bdks derivatives (acceptor) binary system induces deeply red-shifted emission of charge-transfer complexes and exciplexes with a large bathochromic shift up to ∼170 nm relative to conventional monomeric luminescence. The results of quantum chemistry simulation are in agreement with the experiment data. Luminescence color tuning of the film are capable by the dye concentration, the donor-acceptor properties of the dye substituents and even the excitation wavelength. White light broad spectrum of a dual luminescence of the investigated binary systems has CIE chromaticity coordinates (0.35; 0.33) close to the standard neutral white light CIE coordinates (0.33; 0.33). This study will facilitate photophysical research and industrial applications of donor-acceptor binary systems based on polymer materials.

The design and synthesis of 1-phenylimidazo[1,5-a]pyridine – anthracene-based fluorophore for greenish-yellow organic light emitting diode and warm white LED

Solution-processed OLEDs offer a promising and affordable technology for solid-state lighting and superior self-luminous display panels. Herein, an imidazo[1,5-a]pyridine (ImPy)-based fluorophore decorated with an aromatic π-system anthracene is synthesized by a one-pot condensation approach. From the theoretical study, the energy difference between HOMO and LUMO is 3.1 eV. The molecule shows excellent thermal stability and electrochemical stability. It exhibits efficient intramolecular charge transfer and displays a positive solvatochromic photoluminescence emission band ranging from 528 nm in hexane to 586 nm in acetonitrile with large Stokes’ shift of ∼11,000 cm−1. The OLEDs made of this emitter displayed good device performance with luminous efficiency of 4.4 cd A–1, power efficiency of 2.2 lm W–1 and external quantum efficiency of 3.2%. Additionally, this OLED emitted greenish-yellow light with CIE coordinate (0.34, 0.45) and possessed a low turn-on voltage of 7 V. The material also used in white LED fabrication and the fabricated white LED displayed an excellent color rendering index (CRI), the luminous efficiency of radiation (LER), and correlated color temperatures (CCT) of 89328 lm W–1 , and 4907 K, respectively with CIE coordinate (0.35,0.32).

Modulating electronic confinement and structural distortion of multiple resonance emitters enables high-performance ultrapure blue OLED

Developing deep-blue emitters with high color purity is crucial for the advancement of ultrahigh-definition display technology based on organic light-emitting diodes (OLEDs). Since most emitters are empirically designed, establishing a feasible design strategy for developing ultrapure blue emitters with narrowband characteristics remains an urgent and challenging goal. Here, we subtly construct four blue emitters with multiple resonance (MR) effect and provide an in-depth understanding for the nature of narrowband emission from the perspective of electronic confinement and structural distortion combined with actual molecular structures. A novel and feasible molecular design strategy is proposed based on the “flexible locking-ring” concept, enabling effective narrowing main peak while retaining bluer emission. More impressively, a simple sensitizer-free OLED based on SAC2MN2B with the “flexible locking-ring” design achieves one of state-of-the-art device performance with a maximum external quantum efficiency of 19.80 %, and a pure deep-blue emission peaking at 448 nm with small full-width at half-maximum (FWHM) of 25 nm and CIE coordinates of (0.147, 0.061). This work successfully achieves high-performance OLED with high color purity and provides a feasible and promising design strategy for developing organic emitters with ultrapure blue emission.