Phosphorescence Quantum Research Articles

Time‐Resolved and Blue‐Shifted Pure Room‐Temperature Phosphorescence by Dynamic Isolation of Triplet Exciton in Crystal

AbstractOrganic room‐temperature phosphorescence (RTP) with rich photophysical properties has attracted great interest, but it remains a big challenge to realize pure RTP without fluorescence in steady‐state photoluminescence (SSPL) and blue‐shifted RTP that intrinsically restricted by the spin‐forbidden intersystem crossing (ISC) and the radiative decay of the low‐lying triplet excited state. Herein, two fluorescence‐free RTP molecules based on β‐diketone‐bridged phenoselenazine/phenothiazine are developed, which contain either Se or S heteroatom in the phosphor to significantly promote ISC; and, both isolated and J‐aggregated phosphors are formed in crystal, where the J‐aggregation can not only facilitate the ISC for pure RTP but also strength the emission for high phosphorescent quantum yield of 22.3%, while the isolated phosphor affords longer RTP lifetime up to 131 ms. Excitingly, blue‐shifted (35 nm compare to SSPL) pure RTP from yellow‐green (525 nm) to cyan (490 nm) that dynamically depending on the time and temperature is observed for the first time. Experimental and theoretical results indicate that the regulation of time/temperature‐dependent RTP is attributed to the different lifetimes of the isolated and aggregated emission owing to the dynamic competition between different accumulation modes of phosphors in crystal aided by the interrupted conjugation by the sp3 C of β‐diketone.

Ultrafast dynamics of mCP and Br-mCP: Insights from transient absorption spectroscopy

Heavy atom activated organic room-temperature phosphorescence (RTP) has attracted considerable interest due to its high phosphorescence quantum yield and prolonged lifetime. This research provides a detailed analysis of the transient absorption spectroscopy of 1,3-Bis(N-carbazolyl)benzene (mCP) and 9,9'-(5-Bromo-1,3-phenylene)bis(9H-carbazole) (Br-mCP) in toluene solution. In the femtosecond transient absorption (fs-TA) spectroscopy of mCP, the excited state absorption (ESA) signal decreases at 630 nm while the triplet-triplet absorption (TTA) signal increases at 420 nm. Meanwhile, the isosbestic point observed at 455 nm indicates an intersystem crossing (ISC) lifetime of 15.4 ns. Moving on to the nanosecond transient absorption (ns-TA) spectroscopy, the TTA signal reaches its peak at 27.3 ns before decreasing, with the triplet lifetime of mCP measured at 2.8 μs. Br-mCP exhibits a similar dynamic evolution to mCP, but with a quicker ISC process (9.4 ns) and a longer triplet lifetime (3.9 μs). The quicker ISC process in Br-mCP is ascribed to the presence of heavy atom in the molecular structure, leading to an enhanced spin-orbit coupling constant (ξ(S1, T3)Br-mCP = 1.371 cm-1 > ξ(S1, T4)mCP = 0.060 cm-1). The prolonged triplet lifetime of Br-mCP (3.9 μs > 2.8 μs) results from its lower reorganization energy, effectively reducing non-radiative vibrational energy losses within the molecule. This work significantly enhances our understanding of RTP materials incorporating heavy atoms.

Stable, Full-Color, Long-Lasting Aqueous Room-Temperature Phosphorescent Materials.

Ultralong room-temperature phosphorescent (URTP) materials have garnered significant attention in anti-counterfeiting, optoelectronic displays, and bio-imaging due to their unique optical properties. However, most URTP materials exhibit weak emission or are quenched in aqueous solutions. This study proposes a simple and effective strategy for preparing full-color aqueous URTP materials using a one-step microwave method. Guest molecules are embedded in a rigid cyanuric acid (CA) matrix formed from urea. By enhancing the conjugation of the guest molecules, a series of full-color URTP materials is successfully produced. These materials exhibit excellent phosphorescent properties, with a maximum phosphorescent lifetime of 7.96s. Protected by the CA matrix, they retain phosphorescence even in aqueous environments, displaying an afterglow visible to the naked eye for over 30s in water. Additionally, under low water content conditions, the materials exhibit exceptional water-enhanced properties, achieving a phosphorescence quantum yield (PhQY) of 40.4%. Importantly, these aqueous URTP materials can be prepared in just 5min, showcasing great potential in information encryption and afterglow displays.

Programmable Encryption Patterns from Phosphorescent Polymers Via Laser Controlling Water‐Quenching Effect

AbstractOrganic room temperature phosphorescence (RTP) from polymers holds significant promise for information encryption and anti‐counterfeiting applications. However, conventional patterning techniques limit the development of advanced RTP encryption, highlighting the need for an efficient method that achieves encryption processes quickly and conveniently. In this study, the UV laser marking machine is applied to create traceless phosphorescent patterns by leveraging the photothermal effect of the laser and the water‐absorbent quenching RTP property of polyacrylamide. A series of biaryl derivative phosphors with low π‐electron numbers are designed to limit UV absorption to below 355 nm, thereby preventing polymer sintering by the UV laser (355 nm). Additionally, two phosphorescent polymers, PB2COOH (phosphorescence lifetime τP = 2.34 s; phosphorescence quantum yield ΦP = 13.59%) and PBN (τP = 1.46 s; ΦP = 20.33%), possessing relatively excellent phosphorescent properties, are obtained. The controllable program and non‐contact processing of the marking machine enable the rapid realization of complex patterns, such as the Twelve Chinese Zodiac Signs, effectively overcoming the constraints of traditional techniques. Based on this laser technology, applications such as dual‐locking QR (quick response) codes, misleading double QR codes, labeling, and other advanced encryption methods are developed.

Blue phosphorescent solid supramolecular assemblies between hydroxypropyl-β-cyclodextrin and triazine derivatives for achieving multicolor delayed fluorescence

Highly efficient blue phosphorescent solid supramolecular assemblies are constructed by three triazine derivatives with different carboxylate substitution positions (TAB, TAC and TAD), hydroxypropyl-β-cyclodextrin (HPCD) and polyvinyl alcohol (PVA). The encapsulation of HPCD to TAB/C/D effectively promotes phosphorescence lifetimes and quantum yields of the guests by the host-guest interaction and hydrogen bonds suppressing the nonradiative decays. Impressively, TAD-HPCD/PVA with blue phosphorescence boasts an ultrahigh phosphorescence quantum yield (ΦP) of 71.65 %. By further separately doping with fluorescent dyes Fluorescein sodium, Rhodamine B and Sulfo-Cyanine5, supramolecular polymeric films with water responsiveness, regulable lifetimes and multicolor delayed fluorescence are obtained via triplet-to-singlet and singlet-to-singlet Förster resonance energy transfer. Polymeric phosphorescence supramolecular materials mediated by HPCD are desirable for optical anti-counterfeiting patterns and information encryption.

Regulating Room-Temperature Phosphorescence of Organic Luminophores Through Stepwise Stabilization by Coordination and In-Situ Precipitation Reaction.

Developing efficiency and long-lived room-temperature phosphorescence (RTP) materials through straightforward methods is highly desired. In this work, a stepwise stabilization strategy was proposed by the coordination and in-situ precipitation reactions among organic precursors, inorganic cation and anions, producing room-temperature phosphorescence materials with high emission efficiency (phosphorescence quantum yield of 45 %). Structural and photophysical characterizations revealed the coordination reaction reduced the energy gaps between singlet and triplet states and stabilized the excited states of the guest molecules. The in-situ precipitation reaction produced a solid matrix, which provided isolated environments for protecting the excitons from quenching. The applications of RTP materials in information encryption were demonstrated. The presented results provided a new clue for producing RTP materials, and extended their applications in wide fields.

Modulating Room‐Temperature Phosphorescence of Phenothiazine Dioxide via External Heavy Atoms

Developing pure organic materials with ultralong lifetimes and balanced quantum efficiency is attractive but challenging. In this study, we propose a novel strategy to investigate external heavy atoms by linking molecular emitters with halogen through a flexible alkyl chain. X‐ray crystal analysis clearly reveal the halogen C‐X‐π interactions, which can be tuned by halogen donors, as well as the distance and geometry between them. Impressively, DOPTZ‐C3Cl featuring a chloride atom as donor, exhibits a balanced long phosphorescence lifetime of 1351 ms and a phosphorescence quantum yield of 10.1%. We also first demonstrate that Cl can induce more positive effect than heavier halogens (Br and I) on prolonging the lifetime. We envisage that the present study will expedite new molecular design to manipulate the room temperature phosphorescence via external heavy atom effect, and highlight a special C‐Cl··π interaction for the development of ultralong phosphorescent materials.

Modulating Room-Temperature Phosphorescence of Phenothiazine Dioxide via External Heavy Atoms.

Developing pure organic materials with ultralong lifetimes and balanced quantum efficiency is attractive but challenging. In this study, we propose a novel strategy to investigate external heavy atoms by linking molecular emitters with halogen through a flexible alkyl chain. X-ray crystal analysis clearly reveal the halogen C-X-π interactions, which can be tuned by halogen donors, as well as the distance and geometry between them. Impressively, DOPTZ-C3Cl featuring a chloride atom as donor, exhibits a balanced long phosphorescence lifetime of 1351 ms and a phosphorescence quantum yield of 10.1 %. We also first demonstrate that Cl can induce more positive effect than heavier halogens (Br and I) on prolonging the lifetime. We envisage that the present study will expedite new molecular design to manipulate the room temperature phosphorescence via external heavy atom effect, and highlight a special C-Cl⋅⋅⋅π interaction for the development of ultralong phosphorescent materials.

Excitation wavelength and time dependent colour tunable room temperature phosphorescence from boron doped carbon nanodots.

Developing metal free room temperature phosphorescence (RTP) materials have received tremendous attention due its potential application in various fields such as sensing, optoelectronics and anticounterfeiting. Herein, we have synthesized an excitation wavelength and time dependent phosphorescent boron doped carbon nanodots (BCNDs) by thermal treatment of ethanolamine and boric acid at 240°C, where boric acid act as both doping and host agents. The obtained BCNDs display blue to orange fluorescence in both aqueous medium and solid state. In addition, the BCNDs display tunable orange-yellow-green phosphorescence in solid state under UV and visible light, lasting upto 10s, visible to naked eye. The boron and nitrogen doping regulates the band gap of the BCNDs, resulting the phosphorescence colour tunability. The average phosphorescence lifetime and quantum yield of BCNDs are found to be 1.27s and 8.61% respectively. Based on the optical properties, the BCNDs are applied as security ink in information encryption and security marking. Hence, this work can promote the development of metal free phosphorescent carbon based materials which may find application in various emerging fields.

Visualization Detection of Ultralow Temperature Based on Flexible Cross–linked Polymer Systems

AbstractUltralow temperature storage has sparked considerable attention with the development of the economy, showing promising applications ranging from biomedical to national defense and other fields. However, the development of ultralow temperature detection is constrained by the brittleness of current materials at low temperatures and the complexity of detection techniques. Consequently, the challenge exists in finding efficient solutions to material tolerance issues and achieving rapid detection of ultralow temperature. Herein, a novel flexible cross–linked polymer TPTA@PU film with long afterglow, high phosphorescence quantum efficiency, and excellent mechanical properties are successfully fabricated. Interestingly, the obtained TPTA@PU films demonstrate a notable thermoresponsive behavior, with the afterglow color shifting rapidly from blue to green within the temperature ranges from 80 to 280 K. Additionally, there is a positive linear correlation between the RGB values of the afterglow color and the corresponding temperature. Based on these prominent features, an ultralow temperature sensor is realized by utilizing TPTA@PU films as thermoresponsive elements. This work can be expected to provide more inspiration and possibilities for using RTP materials in a more cutting‐edge field.

Simultaneous achieving color‐tuning long persistent luminescence and phosphorescent quantum yield of 81.05% in 2D organic metal halide perovskite

AbstractIonically bonded organic metal halide perovskite‐like luminescent materials, which incorporate organic cations and metal halides, have emerged as a versatile multicomponent material system. However, these materials still face challenges in terms of low phosphorescence quantum yields and limited long persistent luminescence (LPL) colors. Herein, we present the design and synthesis of an intraligand charge‐transfer organic‐based metal halide perovskite‐like material, in which organic cations form a compact supramolecular hydrogen‐bonded organic framework (HOF) structure, exhibiting crystallization‐induced phosphorescence emission of ligand, while metal halides form a unique two‐dimensional (2D) structure that displays intrinsic self‐trapped excitons (STE) emission under the radiation of UV light. Notably, the metal halide hybrid is found to exhibit enhanced phosphorescent photoluminescence efficiency of up to 81.05% and tunable LPL from cyan to orange compared to the pristine organic phosphor, due to the structural distortion and scaffolding effects of 2D metal halides as well as a well‐packed HOF structure. Optical characterizations and theoretical calculations reveal that charge transfer from organic cations and halogen to ligand as well as STE from inorganic layers are responsible for the tunable LPL. Meanwhile, the high‐efficiency phosphorescent quantum yield is attributed to stronger hydrogen bond stacking as well as structural distortion of metal halogen bands. Thus, the obtained LPL provides potentials in anti‐counterfeiting, security systems, and so on.

Dynamic Phosphorescence/Fluorescence Switching in Hybrid Metal Halides Toward Time‐Resolved Multi‐Level Anti‐Counterfeiting

AbstractHybrid metal halides (HMHs) with time‐resolved luminescence behavior promise to be a breakthrough in multi‐level anti‐counterfeiting, but controlling the dynamic switching between phosphorescence and fluorescence is extremely challenging. Herein, an array of 0D HMHs is constructed by screening the π‐conjugated ligand with room‐temperature phosphorescence (RTP). Compared to the organic chromophore, (ETPP)2ZrCl6 possesses a misaligned stacking and rigid structure, contributing to an improved phosphorescence quantum yield (ΦP = 27.50%) and an extended phosphorescence lifetime (τ = 0.6234 s), as the intervening of inorganic unit [ZrCl6]2− suppresses the energy losses caused by nonradiative relaxation and prompts the intersystem crossover (ISC) process. Not only that, the interplay of phosphorescence‐fluorescence dual‐mode emission can be intelligently controlled by doping the active metal Te4+, resulting in a dynamic switching between RTP phosphorescence and self‐trapped exciton (STE) fluorescence. DFT calculations reveal the governing origins of RTP‐STE from the intermolecular ISC channels and spin‐orbit coupling (SOC) coefficients. These precise images into periodic pixelated arrays enable the multi‐level anti‐counterfeiting and information encryption. This work proposes a fluorescence‐phosphorescence co‐modulating strategy under the premise of dissecting the structural origins for optimizing RTP phosphorescence, which paves the way for designing high‐security‐level anti‐counterfeiting materials.

Sergeant-and-Soldier Effect in an Organic Room-Temperature Phosphorescent Host-Guest System.

Host-guest systems have emerged as an efficient strategy for promoting organic room temperature phosphorescence (RTP). Despite the advantages of doping guest molecules into a host matrix, the complexity of these systems and the lack of techniques to visualize host-guest interactions at the molecular scale pose significant challenges in understanding the underlying mechanisms. Here, a novel host-guest RTP system is developed by incorporating low concentrations (1-10 mol%) of TPP-4C-BI (guest) into crystalline TPP-4C-Cz (host). Utilizing structural isomerism, the guest molecules are regularly incorporated into the host crystal lattice, resulting in phosphorescence quantum yields almost ten times higher than the pure compounds. The system enabled resolution of the molecular packing of the single crystal through X-ray diffraction, providing unprecedented visualization of host-guest interactions. A "sergeant-and-soldier" effect, where the minority dopant molecules (sergeants) significantly influence the packing arrangement of the host molecules (soldiers), enhances RTP is identified. Further analyses revealed that due to the host molecule's inefficient phosphorescence pathway, its long-lived dark triplets are channeled to the guest via triplet-triplet energy transfer (TTET), allowing the excited energy to radiatively decay more efficiently. These insights advance the understanding of RTP mechanisms and offer practical implications for designing high-efficiency phosphorescent materials.

Organic doped red room-temperature afterglow materials based on 2,3,5-triarylfuro[3,2-b]pyridines through Förster-resonance energy transfer

A series of novel 2,3,5-triarylfuro[3,2-b]pyridines are designed and acquired to be used as the guest molecules in organic doped room-temperature phosphorescence (RTP) system. Phenyl(pyridin-2-yl)methanone which can provide the rigid and tight microenvironment is chosen as the host molecule, which enables the two-component doped materials to emit RTP emissions of 0.5–8 s with 41–565 ms phosphorescence lifetimes and 2.9–19.4 % phosphorescence quantum efficiencies through constricting the non-radiative decay of triplet excitons. Furthermore, using commercial dyes Erythrosin B sodium salt and Eosin Y sodium salt as the third component and energy acceptor, the three-component materials emit bright red afterglows of 2 s with delayed lifetimes of 252–286 ms and emission quantum yields of 5.1–5.6 %, which are demonstrated to come from the triplet-to-singlet Förster-resonance energy transfer (FRET) from phosphorescence emission of 2,3,5-triarylfuro[3,2-b]pyridine derivative to fluorescence emission of commercial dye. This work not only provides valuable reference for the development of furo[3,2-b]pyridine-based afterglow materials, but also proves that the strategy of the FRET process provides new possibilities for molecules that can only emit fluorescence to participate in constructing afterglow materials.

Room-temperature phosphorescence and aggregation behavior in chiral heavy-atom-free organic molecules

Purely organic room temperature phosphorescence materials (RTP) have attracted much attention recently, but most of them are substituted with heavy atoms to enhance the intersystem crossing (ISC), which requires complicated design and synthesis. Herein, we report four chiral heavy-atom-free small molecules which integrate properties of aggregation and long-lifetime room temperature phosphorescence. The phosphorescence lifetime of synthesized chiral molecules is measured to be 150 ms, and the phosphorescence quantum yield reaches 15 % at room temperature. The twisted chiral conformation of four molecules not only affect aggregation photoluminescence properties but also can synergistically stabilize triplet exciton in the triplet excited states for excellent ISC efficiency. This strategy enriches the application fields of chiral aggregated long-lifetime room temperature phosphorescent materials.

Star-shaped multifunctional organic emitters based on N-(2-cyanophenyl) carbazole frameworks: Effects of steric hindrance fluorene and heavy-atom bromine

To investigate the effects of steric hindrance fluorene and heavy-atom bromine on the general optoelectronic properties of star-shaped organic emitters based on 9-(2-cyanophenyl) carbazole (OCzPhCN) frameworks, heavy element of bromine and steric hindrance fluorene were introduced into OCzPhCN to produce four derivatives of 2-(3-bromo-9H-carbazol-9-yl)benzonitrile (BrCzPhCN), 2-(3-bromo-6-(9-(4-ethoxyphenyl)-9H-fluoren-9-yl)-9H-carbazol-9-yl)benzonitrile (BrFCzPhCN), 2-(3-(9-(4-ethoxyphenyl)-9H-fluoren-9-yl)-9H-carbazol-9-yl)benzonitrile (FCzPhCN) and 2-(3,6-bis(9-(4-ethoxyphenyl)-9H-fluoren-9-yl)-9H-carbazol-9-yl)benzonitrile (2FCzPhCN). The fluorene units obviously improve the thermal stability of the obtained compounds, and 2FCzPhCN has the highest thermal stability with 5 % mass heat loss temperature reaching 447 °C. In different polar solvents, the absorption peaks wavelength of OCzPhCN, FCzPhCN and 2FCzPhCN are basically unchanged, and the redshifted emission peaks are positively correlated with solvent polarity. The photoluminescence quantum yields (PLQYs) of OCzPhCN, BrCzPhCN, FCzPhCN, BrFCzPhCN and 2FCzPhCN powders were 20.17 %, 5.43 %, 30.75 %, 3.27 % and 23.56 %. The fluorescence and phosphorescent quantum efficiencies of OCzPhCN, BrCzPhCN, FCzPhCN, BrFCzPhCN and 2FCzPhCN powders are 9.76 % and 10.41 %, 1.2 % and 3.23 %, 28.45 % and 2.3 %, 3.27 % and 0 %, 23.56 % and 0 %. OCzPhCN, BrCzPhCN and FCzPhCN powders show obvious room temperature phosphorescent emission, and the phosphorescent emission lifetime of OCzPhCN, BrCzPhCN and FCzPhCN powders at 561 nm, 576 nm and 568 nm are 193.17 ms, 18.65 ms and 7.25 ms. Compared with OCzPhCN, the introduction of bromine decreases the PLQY and the phosphorescent lifetime of BrCzPhCN powder, while the fluorescence quantum efficiency of the compound FCzPhCN powder has been improved. The corresponding single-triplet energy splitting (ΔEST) of OCzPhCN, FCzPhCN and 2FCzPhCN in solutions are 0.49 eV, 0.63 eV and 0.63 eV, and the corresponding ΔEST values of OCzPhCN, BrCzPhCN FCzPhCN powders are 1.19 eV, 0.74 eV and 0.55 eV. The steric hindrance fluorene units result in smaller and stabilized ΔEST in the solid powder states, and the same situation is opposite in the unimolecular solutions. The maximum external quantum efficiency of organic light-emitting diode based on 10,10′-(4,4′-sulfonylbis (4,1-phenylene)) bis (9,9-dimethyl-9,10-dihydroacridine) hosted by OCzPhCN reaches 12.7 %, and the external quantum efficiency at 100 cd/m2 rolls down to 11 %. OCzPhCN is the best emitters in terms of room temperature phosphorescent emission and host applications.

Enabling efficient and ultralong room-temperature phosphorescence from organic luminogens by locking the molecular conformation in polymer matrix

Tackling the challenge of developing ultralong organic phosphorescence (UOP) materials with a high phosphorescence quantum yield (Φphos.) and an ultralong phosphorescence lifetime (τphos.) under ambient conditions is urgently needed. Herein, typical organic luminogens with simple chemical structures, namely, triphenylamine (TPA), 9-phenylcarbazole (PCz), and indolo[3,2,1-jk]carbazole (ICz), are doped into a melamine–formaldehyde (MF) polymer matrix with a compact three-dimensional covalent network to prepare UOP materials, respectively. Both experiments and theoretical calculations suggest that restricting intramolecular motions to suppress the nonradiative decay of triplet excitons plays a critical role in achieving ultralong room-temperature phosphorescence from organic molecules in polymer matrices. The luminophore ICz with a planar and rigid chemical structure, constructed by locking the molecular conformation of TPA via carbon–carbon single bonds, exhibits a bright organic afterglow with a Φphos. up to 38.31 % and a τphos. up to 2.73 s in the MF polymer under ambient conditions, representing one of the most excellent polymer-based organic afterglow materials in comprehensive UOP performance. The gradual enhancement in UOP of the resulting luminescent materials has led to their successful use in multi-level anti-counterfeiting. This work provides an effective strategy for developing organic afterglow materials with both high Φphos. and τphos. values.

Unique Organic Crystal Skeleton Based on N-Phenyl-Carbazole Derivatives with Adjustable Room Temperature Phosphorescence and Highly Stable Inclusion Ability to Dichloromethane.

Monosubstituted 9-(2-bromophenyl)-carbazole (1Br1CZ) and disubstituted 9,9'-(2,4-dibromo-1,3-phenylene) bis(9H-carbazole) (2Br2CZ) are synthesized by introducing bromine into ortho-phenyl position of 9-phenyl-carbazole (PhCZ). The decomposition temperature with 5% mass loss and melting point of 2Br2CZ crystal are 360 and 230°C. The highest occupied molecular orbital energy level of PhCZ is the highest, and that of 2Br2CZ is the lowest. The crystals of PhCZ, 1Br1CZ, and 2Br2CZ are monoclinic, orthorhombic, and triclinic system, which exhibit room temperature phosphorescence with lifetimes of 171.81, 37.15, and 28.77ms, and their corresponding phosphorescence quantum yields are 0.83%, 0.16%, and 4.58%. It theoretically reveals that six triplet energy levels (T1-T6) exist under S1 in 2Br2CZ crystal, and the spin orbit coupling constants between S1 and Tn in 2Br2CZ are also greater than those in PhCZ and 1Br1CZ, which promotes the intersystem crossing. Meanwhile, through crystal structure and Hirshfeld surface analysis, the torsion angles between the carbazole unit of 2Br2CZ and the central phenyl group reached 85.28°. The 2Br2CZ crystal exhibits the richest intermolecular interactions. A cavity of 4.498Å is formed within the crystal skeleton of 2Br2CZ, which can precisely fixe dichloromethane with a record-high desorption temperature over 145°C.

Carbon Quantum Dots with Highly Efficient Bandgap Emission for Electroluminescent Light-Emitting Diodes

Carbon quantum dots (CQDs) feature bright and tunable photoluminescence, solution processability, and low toxicity, showing great potential in optoelectronics. The multicolor fluorescent CQDs were first fabricated as active layers in our lab, and then the high-performance electroluminescent warm white light-emitting diodes (LEDs) were obtained with the synthesized bright red CQDs. More significantly, through designing the triangular structure of the carbon core, fluorescent CQDs first achieved the narrow-bandwidth (∼30 nm) electroluminescent LEDs with appreciable stability, high color purity, and high luminescence performance. These results lay the foundation for the development of next-generation high performance displays based on CQDs. Here, we will report the large-scale synthesis of CQDs with near-unity photoluminescence quantum yield and the synthesis of red (625 nm) phosphorescent carbon quantum dot organic frameworks (CDOFs) with a quantum yield of up to 42.3% and realization of high-efficiency red phosphorescent electroluminescent LEDs. The LEDs based on the CDOFs exhibited a red emission with a maximum luminance of 1818 cd m−2 and an EQE of 5.6%. This work explores the possibility of a new perspective for developing high-performance CQD-based electroluminescent LEDs.References Yuxin Shi, Louzhen Fan, et al., Red Phosphorescent Carbon Quantum Dot Organic Framework-Based Electroluminescent Light-Emitting Diodes Exceeding 5% External Quantum Efficiency, Am. Chem. Soc. 2021, 143, 45, 18941–18951Ting Yuan, Louzhen Fan, et al., Carbon Quantum Dots with Near-Unity Quantum Yield Bandgap Emission for Electroluminescent Light-Emitting Diodes, Angew. Chem. Int. Ed. 2023, e202218568.Fanglong Yuan，Louzhen Fan, et al., Engineering triangular carbon quantum dots with unprecedented narrow bandwidth emission for multicolored LEDs, Nat. Commun., 2018, 9, 2249. Figure 1

Enhancing the Room-Temperature Phosphorescence Performance by Salinization of Guests.

Although the host-guest doped strategy effectively improves the phosphorescence performance of materials and greatly enriches the variety of materials, most of the guests are organic molecules with weak luminescence ability, which leads to the need for further improvement in the phosphorescence performance of doped materials. Herein, by salinization of organic molecules, the luminescence performance of the guests was effectively improved, thereby significantly enhancing the phosphorescence performance of the doped system. A compound 4-(naphthalen-2-yl)quinoline (QL) containing nitrogen atom was synthesized as initial guest, then QL was salted to obtain six organic salt guests containing anions BF4-, PF6-, CF3SO3-, N(CF3SO2)2-, ClO4-, and C4F9SO3-, respectively. Two doped systems were constructed using benzophenone and poly(methyl methacrylate) as the hosts. The phosphorescence quantum yield and phosphorescence lifetime of doped materials with QL as guest were only 4.1%/5.2% and 131 ms/141 ms, while those of doped materials with salinized molecules as guests were improved to 32-39% and 534-625 ms, respectively. The single-crystal structures and theoretical calculations indicated that anions can not only enhance the intermolecular interaction of guests but also increase the spin-orbit coupling constant. This work provides an effective strategy for improving the phosphorescence performance of doped materials.