International Commission On Illumination Research Articles

Efficient and Stable Narrowband Pure-Red Light-Emitting Diodes with Electroluminescence Efficiencies Exceeding 43.

Advanced multiresonance-induced thermally activated delayed fluorescence (MR-TADF) materials exhibit exceptional promise for applications in state-of-the-art organic light-emitting diodes (OLEDs) owing to their unique narrowband emissions and high luminescent efficiencies. Despite substantial progress with blue and green MR-TADF materials, the development of pure-red MR-TADF emitters has lagged behind, thereby hindering the advancement toward high-performance ultrahigh-definition OLED displays. Here, we propose an effective approach for designing pure-red MR-TADF molecules based on the integration of secondary electron-donating units and π-skeleton extension into MR cores, which enables not only a redshift of narrowband emission but also an acceleration of reverse intersystem crossing (RISC) rate. The proof-of-the-concept emitter BNTPA showcases a bright and saturated red emission centered at 613 nm with a full-width at half-maximum of 0.14 eV, together with a more than twofold increase in the RISC rate. As a result, TADF OLEDs based on BNTPA achieved a record maximum external quantum efficiency (EQEmax) of up to 35.2% with Commission Internationale de l'Eclairage (CIE) coordinates of (0.657, 0.343), approaching the coordinates of the National Television Standards Committee (NTSC) red standard. Moreover, phosphor-assisted fluorescence devices exploiting BNTPA as a terminal emitter exhibit an exceptional EQEmax of 43.3%, accompanied by improved operational stability.

Simple‐Structure and Anti‐Quenching Deep‐Blue Multi‐Resonance TADF Emitters Enable High‐Efficiency OLEDs with BT.2020 Blue Gamut

AbstractDeveloping highly efficient pure‐blue organic light‐emitting diodes (OLEDs) that meet the stringent BT.2020 standard by using multi‐resonance thermally activated delayed fluorescence (MR‐TADF) materials has long been a formidable challenge. In this study, a strategy is demonstrated for high‐performance blue MR‐TADF emitters by gradually decorating the MR framework with alkyl groups, and subsequently introducing a diarylamino group at the para‐position of boron atom. The proof‐of‐concept molecule, IPrBN‐mCP, exhibits a narrowband deep‐blue emission peaking at 452 nm, with a very narrow full‐width at half maximum (FWHM) of 19 nm in solution, and a remarkably high photoluminescence quantum yield (PLQY) approaching unity in doped films. As a result, OLEDs based on IPrBN‐mCP achieve not only a high maximum external quantum efficiency (EQEmax) of 33.4% but also ultrapure blue emission with a Commission Internationale de L'Eclairage (CIE) y value of 0.046, fully satisfying the BT.2020 blue standard. This represents the first OLED example fully meeting the rigorous color requirements of the BT.2020 blue standard while simultaneously achieving an EQE exceeding 30%.

Solution Processed Bilayer Metal Halide White Light Emitting Diodes.

Metal halide perovskites and perovskite-related organic metal halide hybrids (OMHHs) have recently emerged as a new class of luminescent materials for light emitting diodes (LEDs), owing to their unique and remarkable properties, including near-unity photoluminescence quantum efficiencies, highly tunable emission colors, and low temperature solution processing. While substantial progress has been made in developing monochromatic LEDs with electroluminescence across blue, green, red, and near-infrared regions, achieving highly efficient and stable white electroluminescence from a single LED remains a challenging and under-explored area. Here, a facile approach to generating white electroluminescence is reported by combining narrow sky-blue emission from metal halide perovskites and broadband orange/red emission from zero-dimensional (0D) OMHHs. For the proof of concept, utilizing TPPcarz+ passivated two-dimensional (2D) CsPbBr3 nanoplatelets (NPLs) as sky blue emitter and 0D TPPcarzSbBr4 as orange/red emitter (TPPcarz+ = triphenyl (9-phenyl-9H-carbazol-3-yl) phosphonium), white LEDs (WLEDs) with a solution processed bilayer structure have been fabricated to exhibit a peak external quantum efficiency (EQE) of 4.8% and luminance of 1507 cd m-2 at the Commission Internationale de L'Eclairage (CIE) coordinate of (0.32, 0.35). This work opens a new pathway for creating highly efficient and stable WLEDs using metal halide perovskites and related materials.

Spiro-Carbon-Locking and Sulfur-Embedding Strategy for Constructing Deep-Red Organic Electroluminescent Emitter with High Efficiency.

The discovery of multiple resonance thermally activated delayed fluorescence (MR-TADF) materials with remarkable narrowband emission has opened a new avenue for the development of organic light-emitting diodes (OLEDs) with high color purity. However, the lack of construction strategies for purely red MR-TADF materials significantly impedes their application in full-color high-definition displays. Herein, we propose a unique and handy approach of spiro-carbon-locking and sulfur-embedding strategy to modify the parent MR-TADF framework, resulting in a red MR-TADF emitter with high color purity. The reported MR-TADF molecule (namely, FSBN) demonstrates a pure red emission with an emission maximum of 621 nm in toluene solution. The OLED with FSBN as emitter exhibits Commission Internationale de l'Éclairage (CIE) coordinates of (0.67, 0.33), which exactly matches the red standard defined by the National Television Standards Committee (NTSC). Importantly, the single-host OLED achieves a high power efficiency (PE) of up to 50.1 lm W-1, suggesting the potential for the development of low power consumption red OLEDs.

Spiro‐Carbon‐Locking and Sulfur‐Embedding Strategy for Constructing Deep‐Red Organic Electroluminescent Emitter with High Efficiency

The discovery of multiple resonance thermally activated delayed fluorescence (MR‐TADF) materials with remarkable narrowband emission has opened a new avenue for the development of organic light‐emitting diodes (OLEDs) with high color purity. However, the lack of construction strategies for purely red MR‐TADF materials significantly impedes their application in full‐color high‐definition displays. Herein, we propose a unique and handy approach of spiro‐carbon‐locking and sulfur‐embedding strategy to modify the parent MR‐TADF framework, resulting in a red MR‐TADF emitter with high color purity. The reported MR‐TADF molecule (namely, FSBN) demonstrates a pure red emission with an emission maximum of 621 nm in toluene solution. The OLED with FSBN as emitter exhibits Commission Internationale de l’Éclairage (CIE) coordinates of (0.67, 0.33), which exactly matches the red standard defined by the National Television Standards Committee (NTSC). Importantly, the single‐host OLED achieves a high power efficiency (PE) of up to 50.1 lm W−1, suggesting the potential for the development of low power consumption red OLEDs.

Hybrid Local and Charge Transfer Emitters Utilizing Hyperconjugation Effect Towards Solution‐Processed Ultra‐Deep‐Blue OLEDs with External Quantum Efficiency Approaching 12 %

AbstractHybrid local and charge transfer (HLCT) excited state materials, which possess weak donor‐acceptor (D–A) pure organic structures, deserve one of the most promising efficient and stable blue emitters. Through high‐lying reverse intersystem crossing (hRISC) process, 75 % triplet excitons generated by electrical excitation could be harvested and utilized in organic light‐emitting diodes (OLEDs). However, there are still significant challenges to achieve high‐efficiency ultra‐deep‐blue HLCT emitters with low Commission Internationale de l'Eclairage (CIE) 1931 chromaticity coordinate y values. Here, a series of novel blue HLCT emitters based on spiro[1,8‐diazafluorene‐9,2′‐imidazole] structure were designed and synthesized by fine‐tuning the spiro[fluorene‐9,2′‐imidazole] core structure in our previous work through heteroatom substitution and hyperconjugation effect. The target emitters were endowed with excellent photophysical and electrochemical merits, thermal stability and solution processibility. The solution‐processed OLED based on 4′,5′‐bis(4‐(9H‐carbazol‐9‐yl)phenyl)spiro[1,8‐diazafluorene‐9,2′‐imidazole] (NFIP‐CZ) achieved efficient ultra‐deep‐blue emission (CIEx,y=0.1581, 0.0422) with the maximum external quantum efficiency (EQEmax), maximum current efficiency (CEmax) and maximum power efficiency (PEmax) of 11.94 %, 4.07 cd ⋅ A−1 and 2.56 lm ⋅ W−1. The record EQE is a breakthrough in both solution‐processed and vacuum vapor deposition ultra‐deep‐blue HLCT OLEDs currently.

Efficient Deep-Blue Fluorescent OLEDs Based on a D-π-A Emitter Profiting From Intramolecular Hydrogen Bonds and a Hybridized Excited State.

High performance deep-blue emitters with a Commission International de l'Eclairage (CIE) coordinate of CIEy≤0.08 are highly desired in ultrahigh-definition displays. Herein, we designed and synthesized an efficient D-π-A deep-blue emitter, 2-(6-([1,1' : 3',1''-terphenyl]-5'-yl)pyridin-3-yl)-1-phenyl-1H-phenanthro[9,10-d] imidazole (mPTPH), using the synergistic effect of intramolecular hydrogen bond (H-bond) and hybridized excited state. Single-crystal structure analysis confirmed that there exist intra- and intermolecular H-bond interactions which could inhibit the structure vibration and increase photoluminescence efficiency. The photophysical and theoretical results show that mPTPH exhibited hybridized local and charge-transfer (HLCT) feature with strong deep-blue emission. Ultimately, the non-doped device based on mPTPH exhibited high maximum luminance of 20610 cd m-2. The doped device achieved high maximum external quantum efficiency of 5.4 % and small efficiency roll-off with deep-blue emission peak of 413 nm and CIE coordinate of (0.16, 0.08).

Modulating Charge-Transfer Excited States of Multiple Resonance Emitters via Intramolecular Covalent Bond Locking.

Advanced multiple resonance thermally activated delayed fluorescence (MR-TADF) emitters with high efficiency and color purity have emerged as a research focus in the development of ultra-high-definition displays. Herein, we disclose an approach to modulate the charge-transfer excited states of MR emitters via intramolecular covalent bond locking. This strategy can promote the evolution of strong intramolecular charge-transfer (ICT) states into weak ICT states, ultimately narrowing the full-width at half-maximum (FWHM) of emitters. To modulate the ICT intensity, two octagonal rings are introduced to yield molecule m-DCzDAz-BNCz. Compounds m-CzDAz-BNCz and m-DCzDAz-BNCz exhibit bright light-green and green fluorescence in toluene, with emission maxima of 504 and 513 nm, and FWHMs of 28 and 34 nm, respectively. Sensitized organic light-emitting diodes (OLEDs) employing emitters m-CzDAz-BNCz and m-DCzDAz-BNCz exhibit green emission with peaks of 508 and 520 nm, Commission Internationale de L'Eclairage (CIE) coordinates of (0.12, 0.65) and (0.19, 0.69), and maximum external quantum efficiencies (EQEs) of 30.2 % and 32.6 %, respectively.

Au···I coinage bonds: Boosting photoluminescence efficiency and solid‐state molecular motion

AbstractCoinage bonds, a type of noncovalent interaction, occur between group 11 elements (Au, Ag, and Cu) with electron donor groups. Despite theoretical validation, empirical evidence remains limited. In this study, an aggregation‐induced emission (AIE)‐active Au(I) complex, ITCPAu, which exhibits Au···I coinage bonds, was revealed based on the single‐crystal X‐ray diffraction and theoretical calculations. Further examination of the luminescence properties of the ITCPAu revealed multiswitchable behavior, including mechanochromism and thermochromism. Nearly pure white‐light emission was achieved with Commission Internationale de L'Eclairage (CIE) 1931 chromaticity coordinates of (0.30, 0.31) by grinding the green‐emissive ITCPAu monomer crystals. Moreover, visualization and manipulation of solid‐state molecular motion (SSMM) in the yellow‐emissive ITCPAu dimer crystals, driven by the robust Au···I coinage bonds, were revealed through a combination of crystal engineering and luminescent properties. Furthermore, to support the robust Au···I coinage bonds, a versatile carrier for small solvent molecules in crystal lattices was developed for uptake and release. Our findings provide experimental and theoretical evidence for Au···I coinage bonds, highlighting their ability to boost photoluminescence quantum yield (PLQY) and trigger SSMM, emphasizing their potential in developing smart materials with stimuli‐responsive properties.

Enhanced Emitting Dipole Orientation Based on Asymmetric Iridium(III) Complexes for Efficient Saturated-Blue Phosphorescent OLEDs.

Three novel asymmetric Ir(III) complexes have been rationally designed to optimize their emitting dipole orientations (EDO) and enhance light outcoupling in blue phosphorescent organic light-emitting diodes (OLEDs), thereby boosting their external quantum efficiency (EQE). Bulky electron-donating groups (EDGs), namely: carbazole (Cz), di-tert-butyl carbazole (tBuCz), and phenoxazine (Pxz) are incorporated into the tridentate dicarbene pincer chelate to induce high degree of packing anisotropy, simultaneously enhancing their photophysical properties. Angle-dependent photoluminescence (ADPL) measurements indicate increased horizontal transition dipole ratios of 0.89 and 0.90 for the Ir(III) complexes Cz-dfppy-CN and tBuCz-dfppy-CN, respectively. Analysis of the single crystal structure and density functional theory (DFT) calculation results revealed an inherent correlation between molecular aspect ratio and EDO. Utilizing the newly obtained emitters, the blue OLED devices demonstrated exceptional performance, achieving a maximum EQE of 30.7% at a Commission International de l'Eclairage (CIE) coordinate of (0.140, 0.148). Optical transfer matrix-based simulations confirmed a maximum outcoupling efficiency of 35% due to improved EDO. Finally, the tandem OLED and hyper-OLED devices exhibited a maximumEQE of 44.2% and 31.6%, respectively, together with good device stability. This rational molecular design provides straightforward guidelines to reach highly efficient and stable saturated blue emission.

Pyrene-encapsulated light-emitting π-conjugated polymer with excellent ozone tolerance capacity for large-area and flexible ultra-deep-blue PLEDs with CIEy = 0.08

Emerging flexible polymer light-emitting diodes (PLEDs) are crucial for the development of information display and solid lighting. However, achieving ultrastable light-emitting polymers with robust emissions and outstanding chem-physic stabilities, remains a serious challenge due to the intrinsic oxidative and degrading properties of aromatic units. Herein, we present a universal and convenient pyrene-encapsulation strategy to enhance the ozone tolerance capacity of deep-blue light-emitting conjugated polymers (PPyDPF) for the narrowband flexible PLEDs. More intestingly, compared to the comparison polymers, PPyDPF showed a lower free volume ratio of 71.78 %, facilitating dense interchain packing, which contributes to its excellent ozone tolerance capacity. Large-area PLEDs were fabricated, which exhibit ultra-deep-blue emission with a FWHM of 40 nm and Commission internationale de l’éclairage (CIE) coordinates of (0.16, 0.08). The demonstrated potential for application in light-emitting devices underscores the significance of this approach, providing an effective strategy for developing aging-resistant light-emitting conjugated polymers for optoelectronic applications.

Ultrabroadband chromaticity-programmable random lasing based on waveguide-assisted pumping strategy

Chromaticity-tunable random lasers (RLs) have wide applications in laser display and imaging. However, the achievable chromaticity range poses challenges due to their inherent randomness and the inevitable loss. Here, an ultrabroadband chromaticity-programmable RL has been demonstrated via waveguide-assisted pumping strategy. The unique configuration with destroyed waveguide supplies an excellent platform for achieving full color random lasing through the cascade pumping process. Random lasing with tunable wavelengths spanning the entire visible range is achieved via side-pumping schemes. The eight acceptor RLs can be simultaneously pumped to obtain chromaticity-programmable random lasing, showcasing a Commission Internationale de l'Eclairage (CIE) color map with 155% more perceptible colors than the standard red-green-blue space. This opens the possibilities for programmable RLs with potential applications in biological imaging and smart sensing.

Hybrid Local and Charge Transfer Emitters Utilizing Hyperconjugation Effect Towards Solution-Processed Ultra-Deep-Blue OLEDs with External Quantum Efficiency Approaching 12.

Hybrid local and charge transfer (HLCT) excited state materials, which possess weak donor-acceptor (D-A) pure organic structures, deserve one of the most promising efficient and stable blue emitters. Through high-lying reverse intersystem crossing (hRISC) process, 75% triplet excitons generated by electrical excitation could be harvested and utilized in organic light-emitting diodes (OLEDs). However, there are still significant challenges to achieve high-efficiency ultra-deep-blue HLCT emitters with low Commission Internationale de l'Eclairage (CIE) 1931 chromaticity coordinate y values. Here, a series of novel blue HLCT emitters based on spiro[1,8-diazafluorene-9,2'-imidazole] structure were designed and synthesized by fine-tuning the spiro[fluorene-9,2'-imidazole] core structure in our previous work through heteroatom substitution and hyperconjugation effect. The target emitters were endowed with excellent photophysical and electrochemical merits, thermal stability and solution processibility. The solution-processed OLED device based on 4',5'-bis(4-(9H-carbazol-9-yl)phenyl)spiro[1,8-diazafluorene-9,2'-imidazole] (NFIP-CZ) achieved efficient ultra-deep-blue emission (CIEx,y = 0.1581, 0.0422) with the maximum external quantum efficiency (EQEmax), maximum current efficiency (CEmax) and maximum power efficiency (PEmax) of 11.94%, 4.07 cd·A-1 and 2.56 lm·W-1. The record EQE is a breakthrough in both solution-processed and vacuum vapor deposition ultra-deep-blue HLCT-OLEDs currently.

Superbly Efficient and Stable Ultrapure Blue Phosphorescent Organic Light-Emitting Diodes with Tetradentate Pt(II) Complex with Vibration Suppression Effect.

Blue phosphorescent organic light-emitting diodes (PHOLEDs) are on the brink of commercialization for decades. However, the external quantum efficiency (EQE) and operational lifetime of PHOLEDs are not yet reached industrial standards. Here, a novel tetradentate Pt(II) emitter with a spirofluorene onto the carbazole unit that minimizes the vibration modes, corresponding to the structural relaxation during the de-excitation, called the vibration suppression effect is reported. This modification reduces the intensity of the second peak in the spectrum and Shockley-Read-Hall recombination by blocking direct hole injection into the emitter while enhancing Förster resonance energy transfer, resulting in 451h of LT50 (the time until a 50% decrease in initial luminance at 1000cdm-2) and 25.1% of the maximum EQE (EQEmax). Thanks to the vibration suppression effect, an extremely narrow full width at half a maximum of 22nm is obtained. In phosphor-sensitized thermally activated delayed fluorescent OLED, ultra-pure blue emission with Commission internationale de l'Eclairage (CIE) coordinates of (0.136, 0.096) is obtained with 28.1% of EQEmax. Furthermore, 50.3% of the EQEmax and 589h of LT70 are simultaneously recorded with the two-stack tandem PHOLED, which is the highest EQEmax among 2-tandem and bottom-emission PHOLEDs with CIEy<0.15.

Dual‐Core Engineering for Efficient Deep‐Blue Multiple Resonance Thermally Activated Delayed Fluorescent Materials

AbstractDeveloping narrowband blue multiple resonance (MR) organic emitters with Commission Internationale de L'Eclairage (CIE) y coordinates &lt;0.1 is essential for advanced display technologies. This study proposes a deep‐blue thermally activated delayed fluorescence (TADF) emitter, named 2BNO, which integrates two independent MR cores. Unlike many TADF materials with single‐bonded dual emitting cores, 2BNO utilizes a steric hindrance‐assisted fluorene bridge to achieve an orthorhombic molecular structure. The dual‐core MR‐TADF emitter shows enhanced light absorption and a high photoluminescence quantum yield. Notably, the emission of 2BNO is not significantly redshifted compared to single‐core compounds and maintains a narrow full width at half‐maximum (FWHM) of 24 nm with CIE coordinates of (0.147, 0.041) in 2Me‐THF solution, nearing the BT.2020 blue standard. Organic light‐emitting diodes (OLEDs) incorporating 2BNO as the emitter exhibit deep‐blue emission at 460 nm with a narrow FWHM of 29 nm and CIE coordinates of (0.14, 0.09). The dual emitting core design significantly improves device efficiency, achieving a high external quantum efficiency (EQE) of 19.8%. The dual‐core molecular design strategy in this work is demonstrated to be effective in promoting the efficiency of the TADF emitters while preserving deep‐blue color purity.

Modulating Charge‐Transfer Excited States of Multiple Resonance Emitters via Intramolecular Covalent Bond Locking

AbstractAdvanced multiple resonance thermally activated delayed fluorescence (MR‐TADF) emitters with high efficiency and color purity have emerged as a research focus in the development of ultra‐high‐definition displays. Herein, we disclose an approach to modulate the charge‐transfer excited states of MR emitters via intramolecular covalent bond locking. This strategy can promote the evolution of strong intramolecular charge‐transfer (ICT) states into weak ICT states, ultimately narrowing the full‐width at half‐maximum (FWHM) of emitters. To modulate the ICT intensity, two octagonal rings are introduced to yield molecule m‐DCzDAz‐BNCz. Compounds m‐CzDAz‐BNCz and m‐DCzDAz‐BNCz exhibit bright light‐green and green fluorescence in toluene, with emission maxima of 504 and 513 nm, and FWHMs of 28 and 34 nm, respectively. Sensitized organic light‐emitting diodes (OLEDs) employing emitters m‐CzDAz‐BNCz and m‐DCzDAz‐BNCz exhibit green emission with peaks of 508 and 520 nm, Commission Internationale de L'Eclairage (CIE) coordinates of (0.12, 0.65) and (0.19, 0.69), and maximum external quantum efficiencies (EQEs) of 30.2 % and 32.6 %, respectively.

Single-Molecule White Circularly Polarized Photoluminescence and Electroluminescence from Dual-Emission Enantiomers.

The strategy of integrating conformational isomerization donors and chiral acceptors in a single molecule was proposed to construct white circularly polarized luminescence (WCPL) materials in this work. Consequently, a pair of dual-emission enantiomers, namely (R/S)-DO-PTZ, were designed and synthesized, which displayed white emission with blue and yellow dual-emission bands in solution and solid films with Commission Internationale de l'Eclairage (CIE) coordinates of (0.30, 0.33) and (0.33, 0.35), respectively. Meanwhile, (R/S)-DO-PTZ exhibited a high PLQY of up to 67 % in doped films and clear mirror-image WCPL signals with a |glum| value of 3.0×10-3. Moreover, white circularly polarized electroluminescence (WCPEL) based on organic light-emitting diodes (OLEDs) with (R/S)-DO-PTZ as emitters were also achieved with CIE coordinates of (0.32, 0.37) and EQEmax of 4.7 %, representing the state-of-the-art level of white OLEDs based on single-molecule purely organic emitters. By optimizing the device structure, warm WCPEL devices were further obtained with a |gEL| value of 2.8×10-3, CIE coordinates of (0.37, 0.48) and EQEmax of up to 15.6 %. To our knowledge, this is the first report of CP-WOLEDs based on single-molecule purely organic emitters.

High‐Efficiency Deep Red Fluorescent Material with Aggregation Induced Emission and the Application in Organic Light‐Emitting Diodes

AbstractThe development of highly efficient deep red materials with emission wavelength beyond 650 nm remains a big challenge due to the constraints imposed by the energy gap rule. In this work, a donor‐acceptor‐donor type emitter, 4,7‐bis (10‐(4‐(tert‐butyl) phenyl)‐10H‐phenothiazin‐3‐yl) benzo[c][1,2,5] thiadiazole (TBPPTZ) is designed and synthesized. Resulting from the slight twist angle between the donor and acceptor units, TBPPTZ exhibits nearly planar conformation and an extended conjugated structure. TBPPTZ shows a deep red emission peak at 687 nm and aggregation induced emission property with a high photoluminescence quantum yield of 45 % in neat thin film. The optimized organic light‐emitting diode (OLEDs) utilizing TBPPTZ as the non‐doped emissive layer obtains a high external quantum efficiency (EQE) up to 2.51 % with an electroluminescence (EL) peak at 676 nm, aligning with the Commission Internationale de L'Eclairage (CIE) coordinates (0.68, 0.31), which shows a small EQE roll‐off of only 5.6 % at 100 cd m−2. Additionally, the doped OLED achieves an EQE up to 5.09 %, with an EL peak at 656 nm and CIE coordinates of (0.65, 0.34). The findings of this research not only contribute to achieve highly efficient deep red OLEDs but also offer a novel and effective deep red molecular strategy to realize high‐quality OLEDs.

Investigation of red-emitting CaMoO4: Eu3+ phosphor by partitioning of substitutional PO4 3- ions via solid-state reaction method.

To investigate the impact of PO4 3- anionic groups, the trivalent europium ion-doped calcium molybdate (CaMoO3-PO4:xEu3+, where x = 0.5, 1.0, 1.5, 2.0, and 2.5mol%) phosphors were synthesized using the solid-state reaction method. The detailed study of the phosphor materials was carried out by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), optical diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. The XRD results indicate that the substitution of PO4 3- anion and Eu3+ dopant ion did not affect the crystal structures of the CaMoO4 phosphors. Ultraviolet-visible (UV-vis) absorption analysis revealed the change of absorption edge of both un-doped and Eu3+-doped CaMoO4-PO4 phosphors. Under the 394 nm UV-excitation, the recorded PL spectra showed an intense peak at 615 nm corresponding to the Eu3+: 5D0 → 7F2 transition. The results of the Commission Internationale de l'Eclairage (CIE) diagram reported that the color of the emissions lies in the red color zone and there is no change in the CIE coordinates of the overall emission for Eu3+-doped CaMoO4-PO4 as Eu concentration changes. Thus, these observations led to finding the best red components for white light-emitting diode applications.

Gold Coordination-Accelerated Multi-Resonance TADF Emission for Efficient Solution-Processible Ultrapure Deep-Blue OLEDs.

Multi-resonance (MR) type emitters have emerged as highly promising candidates for high-resolution organic light-emitting diodes (OLEDs). However, thermally activated delayed fluorescence (TADF) emissions with simultaneous short excited state lifetimes and ultrapure blue color (a CIEy close to 0.046 and an emission peak > 440 nm) have rarely been obtained for MR emitters. Herein, we report a design of dual gold-coordinated MR molecules to achieve efficient and short-lived ultrapure blue TADF emission. The dinuclear Au(I) complex, namely iPrAuBN, shows a narrowband deep-blue emission with a peak maximum of 448 nm and a full width at half maximum (FWHM) of 29 nm in doped film. The coordination with two Au atoms significantly shortens the delayed fluorescence lifetime to 7.8 μs in comparing with 60.6 μs for the organic analogue. Solution-processed OLED doped with iPrAuBN demonstrates an ultrapure blue electroluminescence with a peak maximum of 442 nm, a FWHM of 19 nm, Commission International de l'Éclairage (CIE) coordinates of (0.154, 0.036), and a maximum external quantum efficiency of 14.8%.