Resonance-Activated Spin-Flipping for Efficient Organic Ultralong Room-Temperature Phosphorescence

Ultraviolet irradiation-responsive dynamic ultralong organic phosphorescence in polymeric systems

Room temperature phosphorescence (RTP) has drawn extensive attention in recent years. Efficient stimulus-responsive phosphorescent organic materials are attractive, but are extremely rare because of unclear design principles and intrinsically spin-forbidden intersystem crossing. Herein, we present a feasible and facile strategy to achieve ultraviolet irradiation-responsive ultralong RTP (IRRTP) of some simple organic phosphors by doping into amorphous poly(vinyl alcohol) matrix. In addition to the observed green and yellow afterglow emission with distinct irradiation-enhanced phosphorescence, the phosphorescence lifetime can be tuned by varying the irradiation period of 254 nm light. Significantly, the dynamic phosphorescence lifetime could be increased 14.3 folds from 58.03 ms to 828.81 ms in one of the obtained hybrid films after irradiation for 45 min under ambient conditions. As such, the application in polychromatic screen printing and multilevel information encryption is demonstrated. The extraordinary IRRTP in the amorphous state endows these systems with a highly promising potential for smart flexible luminescent materials and sensors with dynamically controlled phosphorescence.

Supramolecular Pins with Ultralong Efficient Phosphorescence

Constructing ultralong organic phosphorescent materials possessing a high quantum yield is challenging. Herein, assemblies of purely organic supramolecular pins composed of alkyl-bridged phenylpyridinium salts and cucurbit[8]uril (CB[8]) are reported. Different from "one host with two guests" and "head-to-tail" binding, the binding formation of supramolecular pins is "one host with one guest" and "head-to-head," which overcomes electrostatic repulsion and promotes intramolecular charge transfer. The supramolecular pin 1/CB[8] displays afterglow with high phosphorescence quantum yield (99.38%) after incorporation into a rigid matrix, which is the highest yield reported to date for phosphorescent materials. Moreover, multicolor photoluminescence can be obtained by different excitation wavelengths and ratios of host to guest. Owing to the redshift of the absorption, the supramolecular pins are applied for targeted phosphorescence imaging of mitochondria. This work will provide a reasonable supramolecular strategy to achieve redshifted and efficient phosphorescence both in the solid state and in aqueous solution.

Color-Tunable Aqueous Room-Temperature Phosphorescence Supramolecular Assembly

Developing room-temperature phosphorescence (RTP) materials with color-tunability performance in an aqueous environment is crucial for application in optoelectronic areas to a higher stage, such as multicolor display, visual detection of external stimulus, and high-level information anticounterfeiting, but still faces a formidable challenge. Herein, we propose an efficient design strategy to develop excitation wavelength-responsive RTP supramolecular co-assembly systems of a simple benzoic acid derivative and Laponite (Lap) clay nanoplates in aqueous solution, displaying an ultralong lifetime (0.632 s) and a high phosphorescence quantum efficiency (18.04%) simultaneously. Experimental and theoretical research studies suggest that this distinctive feature is due to the generation of more and efficient intersystem crossing pathways benefiting from the coexistence of isolated and J-aggregation states via controlling the doping of the benzoic acid derivative and the inhibition of phosphorescence quenching by water because of the synergistic effects of robust hydrogen-bonding interactions between Lap and the benzoic acid derivative, J-aggregations of the benzoic acid derivative, and good oxygen tolerance of the Lap clay. By virtue of their excellent RTP performances in aqueous solution, the visual colorimetric detection of Ag⁺ in a water environment was achieved for the first time, and visible and high-level information encryption was accomplished as well.

Simple Vanilla Derivatives for Long-Lived Room-Temperature Polymer Phosphorescence as Invisible Security Inks

Developing novel long-lived room-temperature polymer phosphorescence (RTPP) materials could significantly expand their application scope. Herein, a series of RTPP materials based on eight simple vanilla derivatives for security ink application are reported. Attributed to strong mutual hydrogen bonding with polyvinyl alcohol (PVA) matrix, vanilla-doped PVA films exhibit ultralong phosphorescence emission under ambient conditions observed by naked eyes, where methyl vanillate shows the longest emission time up to 7 s. Impressively, when vanilla-doped PVA materials are utilized as invisible security inks, and the inks not only present excellent luminescent emission stability under ambient conditions but also maintain perfect reversibility between room temperature and 65°C for multiple cycles. Owing to the unique RTPP performance, an advanced anticounterfeiting data encoding/reading strategy based on handwriting technology and complex pattern steganography is developed.

Ultralong and Color-Tunable Room-Temperature Phosphorescence Based on Commercial Melamine for Anticounterfeiting and Information Recognition

Advances have been made in the research on color-tunable organic ultralong room-temperature phosphorescence (OURTP) materials. Due to the high cost of raw materials, complex and strict synthesis conditions, and low yields, it is hard to obtain cheap commercial OURTP materials within a short time. Therefore, it is of practical significance to research and develop new OURTP functions based on commercialized organic materials. In this study, the OURTP characteristics of melamine (MEL), a kind of commercially available, cheap, and pure organic material, were investigated and explored. MEL was found with color-tunable and excellent OURTP, the average lifetime can reach 0.74 s, and the phosphorescence quantum yield can reach 17%. Since the ratio of molecular phosphorescence of MEL to the ultralong phosphorescence mediated by H-aggregation differs with the excitation wavelength and their luminescence life spans are also different, the color of OURTP materials is dependent on both excitation wavelength and time. Moreover, the OURTP characteristics of MEL can be utilized in anticounterfeiting and information identification.

Fluorine-induced aggregate-interlocking for color-tunable organic afterglow with a simultaneously improved efficiency and lifetime

Designing organic afterglow materials with a high efficiency and long lifetime is highly attractive but challenging because of the inherent competition between the luminescence efficiency and lifetime. Here, we propose a simple yet efficient strategy, namely fluorine-induced aggregate-interlocking (FIAI), to realize both an enhanced efficiency and elongated lifetime of afterglow materials by stimulating the synergistic effects of the introduced fluorine atoms to efficiently promote intersystem crossing (ISC) and intermolecular non-covalent interactions for facilitating both the generation of triplet excitons and suppression of non-radiative decays. Thus, the fluorine-incorporated afterglow molecules exhibit greatly enhanced ISC with a rate constant up to 5.84 × 107 s-1 and suppressed non-radiative decay down to 0.89 s-1, resulting in efficient organic afterglow with a simultaneously improved efficiency up to 10.5% and a lifetime of 1.09 s. Moreover, accompanied by the efficient phosphorescence emission especially at cryogenic temperature, color-tunable afterglow was also observed at different temperatures. Therefore, tri-mode multiplexing encryption devices by combining lifetime, temperature and color, and visual temperature sensing were successfully established. The FIAI strategy by addressing fundamental issues of afterglow emission paves the way to develop high-performance organic afterglow materials, opening up a broad prospect of aggregated and excited state tuning of organic solids for emission lifetime-resolved applications.

Organic Resonance Materials: Molecular Design, Photophysical Properties, and Optoelectronic Applications

Organic optoelectronic molecules with resonance effects are a striking class of functional materials that have witnessed booming progress in recent years. Various resonances induced by particularly constructed molecular structures can effectively influence key photophysical processes to afford particular optoelectronic properties of the organic resonance materials. The charge transport behaviors were tuned to be dynamic and self-adaptive; emission spectra were made to be very narrow with high color purity; optical bandgaps were significantly reduced, and intersystem crossing was greatly promoted. Therefore, great success has been achieved in various optoelectronic devices by using organic resonance materials to function as smart host materials with high triplet energies, highly luminescent emitters with high quantum yields and narrow emission bands, efficient organic afterglow molecules, and sensitive fluorescent probes. In this Perspective, material design principles, molecular structures and properties, and device performance of organic resonance materials are highlighted and future directions and challenges for this series of amazing materials are discussed.

Ligand engineering to achieve enhanced ratiometric oxygen sensing in a silver cluster-based metal-organic framework

Ratiometric luminescent oxygen sensing based on dual fluorescence and phosphorescence emission in a single matrix is highly desirable, yet the designed synthesis remains challenging. Silver-chalcogenolate-cluster-based metal-organic frameworks that combine the advantages of silver clusters and metal-organic frameworks have displayed unique luminescent properties. Herein, we rationally introduce -NH₂ groups on the linkers of a silver-chalcogenolate-cluster-based metal-organic framework (Ag₁₂bpy-NH₂) to tune the intersystem crossing, achieving a dual fluorescence-phosphorescence emission from the same linker chromophore. The blue fluorescence component has a 100-nm gap in wavelength and 8,500,000-fold difference in lifetime relative to a yellow phosphorescence component. Ag₁₂bpy-NH₂ quantifies oxygen during hypoxia with the limit of detection of as low as 0.1 ppm and 0.3 s response time, which is visualized by the naked eye. Our work shows that metal cluster-based MOFs have great potential in luminescent sensing, and the longer-lived charge-separated states could find more photofunctional applications in solar energy transformation and photocatalysis.

Long Persistent Luminescence Enabled by Dissociation of Triplet Intermediate States in an Organic Guest/Host System

Organic guest/host systems with long persistent luminescence benefiting from the formation of a long-lived charge-separated state have recently been demonstrated. However, the photogeneration mechanism of such key charge-separated states remains elusive. Here, we report the identification of intermediate triplet states with mixed local excitation and charge-transfer character that connect the initial photoexcited singlet states and the long-lived charge-separated states. Using time-resolved optical spectroscopy, we observe the intersystem crossing from photoexcited singlet charge-transfer states to triplet intermediate states on a time scale of ∼52 ns. Temperature-dependent measurements reveal that the long-lived triplet intermediate states ensure a relatively high efficiency of diffusion-driven charge separation to form the charge-separated state responsible for LPL emission. The findings in this work provide a rationale for the development of new LPL materials that may also improve our understanding of the mechanism of photon-to-charge conversion in many organic optoelectronic devices.

Achieving 21% External Quantum Efficiency for Nondoped Solution-Processed Sky-Blue Thermally Activated Delayed Fluorescence OLEDs by Means of Multi-(Donor/Acceptor) Emitter with Through-Space/-Bond Charge Transfer

Although numerous thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs) have been demonstrated, efficient blue or even sky-blue TADF-based nondoped solution-processed devices are still very rare. Herein, through-space charge transfer (TSCT) and through-bond charge transfer (TBCT) effects are skillfully incorporated, as well as the multi-(donor/acceptor) characteristic, into one molecule. The former allows this material to show small singlet-triplet energy splitting (ΔE ST) and a high transition dipole moment. The latter, on the one hand, further lights up multichannel reverse intersystem crossing (RISC) to increase triplet exciton utilization via degenerating molecular orbitals. On the other hand, the nature of the molecular twisted structure effectively suppresses intermolecular packing to obtain high photoluminescence quantum yield (PLQY) in neat flims. Consequently, using this design strategy, T-CNDF-T-tCz containing three donor and three acceptor units, successfully realizes a small ΔE ST (≈0.03 eV) and a high PLQY (≈0.76) at the same time; hence the nondoped solution-processed sky-blue TADF-OLED displays record-breaking efficiency among the solution process-based nondoped sky-blue OLEDs, with high brightness over 5200 cd m-2 and external quantum efficiency up to 21.0%.

Thermally activated triplet exciton release for highly efficient tri-mode organic afterglow

Developing high-efficient afterglow from metal-free organic molecules remains a formidable challenge due to the intrinsically spin-forbidden phosphorescence emission nature of organic afterglow, and only a few examples exhibit afterglow efficiency over 10%. Here, we demonstrate that the organic afterglow can be enhanced dramatically by thermally activated processes to release the excitons on the stabilized triplet state (T₁^*) to the lowest triplet state (T₁) and to the singlet excited state (S₁) for spin-allowed emission. Designed in a twisted donor–acceptor architecture with small singlet-triplet splitting energy and shallow exciton trapping depth, the thermally activated organic afterglow shows an efficiency up to 45%. This afterglow is an extraordinary tri-mode emission at room temperature from the radiative decays of S₁, T₁, and T₁^*. With the highest afterglow efficiency reported so far, the tri-mode afterglow represents an important concept advance in designing high-efficient organic afterglow materials through facilitating thermally activated release of stabilized triplet excitons.

The development of organic afterglow materials that do not contain heavy metals is of interest for biological applications. Here, the authors report on the development of a thermally activated organic molecule with tri-mode afterglow and an afterglow efficiency of up to 45%.

Stimuli-Responsive Circularly Polarized Organic Ultralong Room Temperature Phosphorescence

Purely organic materials showing room temperature phosphorescence (RTP) and ultralong RTP (OURTP) have recently attracted much attention. However, it is challenging to integrate circularly polarized luminescence (CPL) into RTP/OURTP. Here, we show a strategy to realize CPL-active OURTP (CP-OURTP) by binding an achiral phosphor group directly to the chiral center of an ester chain. Engineering of this flexible chiral chain enables efficient chirality transfer to carbazole aggregates, resulting in strong CP-OURTP with a lifetime of over 0.6 s and dissymmetry factor of 2.3×10^-3 after the conformation regulation upon photo-activation. The realized CP-OURTP is thus stable at room temperature but can be deactivated quickly at 50 °C to CP-RTP with high CPL stability during the photo-activation/thermal-deactivation cycles. Based on this extraordinary photo/thermal-responsive and highly reversible CP-OURTP/RTP, a CPL-featured lifetime-encrypted combinational logic device has been successfully established.

Reversible and Continuous Color-Tunable Persistent Luminescence of Metal-Free Organic Materials by "Self"-Interface Energy Transfer

Persistent luminescence from metal-free organic materials is attractive for their ultralong exciton lifetimes. Color-tunable persistent luminescence from single-component organic materials is fascinating but still challenging. By utilizing an efficient approach of "self"-interface energy transfer (IET), the persistent luminescence color of an organic phosphor (CTXO) can be reversibly and continuously tuned by external physical stimuli. Its color circularly changes between green (lifetime = 0.24 s) and deep-yellow (lifetime = 0.10 s) when CTXO is repeatedly triggered with thermal annealing and mechanical grinding. Self-IET from the crystalline part (donor), which exhibits persistent room-temperature phosphorescence, to the amorphous part (acceptor) inside its semicrystal during these treatments is found to be the key exciton process for such novel color modulation. This also provides opportunity for designing stimuli-responsive smart materials with controlled persistent luminescence.

Manipulating the Ultralong Organic Phosphorescence of Small Molecular Crystals

Ultralong organic phosphorescence (UOP) of metal-free organic materials has received considerable attention recently owing to their long-lived emission lifetimes, and the fact that they present an attractive alternative to persistent luminescence in inorganic phosphors. Enormous research effort has been devoted on improving UOP performance in metal-free organic phosphors by promoting the intersystem crossing (ISC) process and suppressing the non-radiative decay of triplet state excitons. This minireview summarizes the recent advances in the rational approaches for manipulating the UOP properties of small molecular crystals, such as phosphorescence lifetime, efficiency, and emission colors. Finally, the present challenges and future development of this field are proposed. This review will provide a guideline to rationally design more advanced metal-free organic phosphorescence materials for potential applications.

X-ray excited ultralong room-temperature phosphorescence for organic afterglow scintillators

An X-ray excited organic afterglow scintillator is realized by embedding lone-pair electron involved n–π* transitions and charge transfer characters into H-aggregations.

Polymorphism-Dependent Dynamic Ultralong Organic Phosphorescence

Developing ultralong organic phosphorescence (UOP) materials with smart response to external stimuli is of great interest in photonics applications, whereas the manipulation of molecular stacking on tuning such dynamic UOP is still a formidable challenge. Herein, we have reported two polymorphs with distinct photoactivated dynamic UOP behavior based on a pyridine derivative for the first time. Our experiment revealed that the dynamic UOP behavior including photoactivation and deactivation feature is highly dependent on irradiation intensity and environmental atmosphere. Additionally, given the unique dynamic UOP feature, these phosphors have been successfully applied to phosphorescence-dependent molecular logic gate and timing data storage. This result not only paves a way to design smart functional materials but also expands the scope of the applications on organic phosphorescence materials.

An ultralong room-temperature phosphorescent material based on the combination of small singlet–triplet splitting energy and H-aggregation

Compound AI-N-Cz exhibited ultralong RTP with a lifetime of 775 ms due to the combination of small ΔE_ST and H-aggregation.

Near-Infrared-Excitable Organic Ultralong Phosphorescence through Multiphoton Absorption

Organic ultralong room-temperature phosphorescence (OURTP) with a long-lived triplet excited state up to several seconds has triggered widespread research interests, but most OURTP materials are excited by only ultraviolet (UV) or blue light owing to their unique stabilized triplet- and solid-state emission feature. Here, we demonstrate that near-infrared- (NIR-) excitable OURTP molecules can be rationally designed by implanting intra/intermolecular charge transfer (CT) characteristics into H-aggregation to stimulate the efficient nonlinear multiphoton absorption (MPA). The resultant upconverted MPA-OURTP show ultralong lifetimes over 0.42 s and a phosphorescence quantum yield of ~37% under both UV and NIR light irradiation. Empowered by the extraordinary MPA-OURTP, novel applications including two-photon bioimaging, visual laser power detection and excitation, and lifetime multiplexing encryption devices were successfully realized. These discoveries illustrate not only a delicate design map for the construction of NIR-excitable OURTP materials but also insightful guidance for exploring OURTP-based nonlinear optoelectronic properties and applications.

Highly Efficient Organic Room-Temperature Phosphorescent Luminophores through Tuning Triplet States and Spin-Orbit Coupling with Incorporation of a Secondary Group

Achieving efficient ultralong purely organic phosphorescent luminophores is still a big challenge due to the slow intersystem crossing (ISC) process. Herein, we present a facile molecular design strategy that incorporates a secondary group (Br atom or methoxy group) into o-BrCz that can significantly enhance the ISC rate constant (k_ISC) and achieve high phosphorescence quantum yields (Φ_P). As a result, DBrCz and MeBrCz achieved a profound increase of k_ISC ≈ 10⁸ s^-1 and obtained excellent Φ_P values up to 24.53 and 27.81% in solid powder, respectively. Given the highly efficient Φ_P and proper τ_p, DBrCz and MeBrCz are applied to alternating current (AC) light-emitting diodes (LEDs), achieving a white LED with CIE coordinates (0.28, 0.29) and a CRI over 90. As a proof of concept, we demonstrate its compensation effect on the dark duration of AC-LED with a reduced percent flicker of 78%. This result extends a new potential application for RTP luminophores in the lighting field.

Excitation-Dependent Long-Life Luminescent Polymeric Systems under Ambient Conditions

Organic room temperature luminescent materials present a unique phosphorescence emission with a long lifetime. However, many of these materials only emit single blue or green color in spite of external stimulation, and their color tunability is limited. Herein, we report a rational design to extend the emission color range from blue to red by controlling the doping of simple pyrene derivatives into a robust polymer matrix. The integration of these pyrene molecules into the polymer films enhances the intersystem crossing pathway, decreases the first triplet level of the system, and ensures the films show a sensitive response to excitation energy, finally yielding excitation-dependent long-life luminescent polymeric systems under ambient conditions. These materials were used to construct anti-counterfeiting patterns with multicolor interconversion, presenting a promising application potential in the field of information security.

Synergistic Intra- and Intermolecular Noncovalent Interactions for Ultralong Organic Phosphorescence

Metal-free ultralong organic phosphorescence (UOP) materials have attracted significant attention owing to their anomalous photophysical properties and potential applications in various fields. Here, three pyrimidine-based organic luminogens, 9-(pyrimidin-2-yl)-9H-carbazole, 9-(4,6-dimethylpyrimidin-2-yl)-9H-carbazole, and 9-(5-bromopyrimidin-2-yl)-9H-carbazole are designed and synthesized, which show efficient yellow UOP with the longest lifetimes up to 1.37 s and the highest absolute phosphorescence quantum yields up to 23.6% under ambient conditions. Theoretical calculations, crystal structures, and photophysical properties of these compounds reveal that intramolecular hydrogen bonding, intermolecular π-π interactions, and intermolecular electronic coupling are responsible for forming dimers and generating highly efficient UOP. Their efficacy as solid materials for data encryption is demonstrated.

Mechanoluminescence or Room-Temperature Phosphorescence: Molecular Packing-Dependent Emission Response

Mechanoluminescence (ML) and room-temperature photophosphorescence (RTP) were achieved in polymorphisms of a triphenylamine derivative with ortho-substitution. This molecular packing-dependent emission afforded crucial information to deeply understand the intrinsic mechanism of different emission forms and the possible packing-function relationship. With the incorporation of solid-state ¹³ C NMR spectra of single crystals, as well as the analysis of crystal structures, the preferred packing modes for ML and/or RTP were investigated in detail, which can guide the reasonable design of organic molecules with special light-emission properties.

Organic Room-Temperature Phosphorescence with Strong Circularly Polarized Luminescence Based on Paracyclophanes

Pure organic materials with intrinsic room-temperature phosphorescence typically rely on heavy atoms or heteroatoms. Two different strategies towards constructing organic room-temperature phosphorescence (RTP) species based upon the through-space charge transfer (TSCT) unit of [2.2]paracyclophane (PCP) were demonstrated. Materials with bromine atoms, PCP-BrCz and PPCP-BrCz, exhibit RTP lifetime of around 100 ms. Modulating the PCP core with non-halogen-containing electron-withdrawing units, PCP-TNTCz and PCP-PyCNCz, successfully elongate the RTP lifetime to 313.59 and 528.00 ms, respectively, the afterglow of which is visible for several seconds under ambient conditions. The PCP-TNTCz and PCP-PyCNCz enantiomers display excellent circular polarized luminescence with dissymmetry factors as high as -1.2×10^-2 in toluene solutions, and decent RTP lifetime of around 300 ms for PCP-TNTCz enantiomers in crystalline state.

Excitation Wavelength-Dependent Dual-Mode Luminescence Emission for Dynamic Multicolor Anticounterfeiting

Luminescent materials have become prevalent in data communication and information security because of their special optical characteristics. Conventional luminescent materials generally exhibit unicolor emission and fixed excitation mode, resulting in decreased efficiency of anticounterfeiting applications. The development of an iridescent chameleon-like material that can change its emission color under different stimulations is a significant challenge. Here, we propose that Pb²⁺, Mn²⁺, and lanthanide cations (such as Y³⁺, Tb³⁺, Yb³⁺) co-doped in Na₂CaGe₂O₆ particles can be an effective tool for designing dual-mode anticounterfeiting materials based on their tunable fluorescence/persistent luminescence transformation and excitation wavelength-dependent emission. Ultimately, a proof-of-concept anticounterfeiting fabric is obtained by using the as-prepared phosphors and exhibits a dynamic multiple color response. This work exploits the possibility of developing a new class of multimode anticounterfeit materials, which would be almost impossible to mimic or counterfeit, providing a very high level of security.

Direct population of triplet excited states through singlet-triplet transition for visible-light excitable organic afterglow

Invoking efficient afterglow in metal-free organic molecules represents an important material advancement. However, organic afterglow suffers from low intensity and efficiency and generally needs to be excited by UV light owing to its spin-forbidden phosphorescent nature that essentially requires facile intersystem crossing (ISC). Here, we propose a strategy to bypass the traditional ISC through facilitating singlet-triplet transition to directly populate triplet excited states from the ground state by combining synergetic effects of both heavy/hetero-atom incorporation and aromatic aggregation. Verified by systematic experimental and computational investigations, this unique singlet-to-triplet absorption results in a much improved organic afterglow quantum efficiency up to 9.5% with a prolonged lifetime of 0.25 s under visible-light irradiation. Fundamentally, this work illustrates for the first time the great potential of the direct population method to red-shift the excitation wavelength and improve the afterglow efficiency, offering important clues for the development of triplet-state involved organic optoelectronic technologies.

Multiple Luminescence Responses towards Mechanical Stimulus and Photo-Induction: The Key Role of the Stuck Packing Mode and Tunable Intermolecular Interactions

Organic luminescence with different forms continues to be one of the most active research fields in science and technology. Herein, an ultra-simple organic molecule (TPA-B), which exhibits both mechanoluminescence (ML) and photo-induced room-temperature phosphorescence (RTP) in the crystalline state, provides an opportunity to reveal the internal mechanism of ML and the dynamic process of photo-induced RTP in the same molecule. Through the detailed investigation of photophysical properties together with crystal structures, the key role of molecular packing and intermolecular interactions was highlighted in the luminescence response by mechanical and light stimulus, affording efficient strategies to design potential smart functional materials with multiple luminescence properties.

Blue-Light-Absorbing Thin Films Showing Ultralong Room-Temperature Phosphorescence

The development of organic materials displaying ultralong room-temperature phosphorescence (URTP) is a material design-rich research field with growing interest recently, as the luminescence characteristics have started to become interesting for applications. However, the development of systems performing under aerated conditions remains a formidable challenge. Furthermore, in the vast majority of molecular examples, the respective absorption bands of the compounds are in the near ultraviolet (UV) range, which makes UV excitation sources necessary. Herein, the synthesis and detailed analysis of new luminescent organic metal-free materials displaying, in addition to conventional fluorescence, phosphorescence with lifetimes up to 700 ms and tailored redshifted absorption bands, allowing for deep blue excitation, are reported. For the most promising targets, their application is demonstrated in the form of organic programmable tags that have been recently developed. These tags make use of reversible activation and deactivation of the URTP by toggling between the presence and absence of molecular oxygen. In this case, the activation can be achieved with visible light excitation, which greatly increases the use case scenarios by making UV sources obsolete.

Facile synthesis of a micro-scale MOF host–guest with long-lasting phosphorescence and enhanced optoelectronic performance

Micro-scale MOF host–guest with tunable phosphorescence and enhanced optoelectronic performance can be obtained by a facile and scalable precipitation process in aqueous solution.

Phthalimide-based “D–N–A” emitters with thermally activated delayed fluorescence and isomer-dependent room-temperature phosphorescence properties

Phthalimide-based “D–N–A” emitters showed TADF and ultralong RTP properties, and could be applied as a security ink in anti-counterfeiting materials.

Bromine-Substituted Fluorene: Molecular Structure, Br-Br Interactions, Room-Temperature Phosphorescence, and Tricolor Triboluminescence

Organic tribophosphorescence materials are rarely reported and the introduction of Br atoms may be a practical way to design such materials. Here four bromine-substituted fluorene-based derivatives are presented and BrFlu-CBr, having fluorescence-phosphorescence dual-emission induced not only by UV light but also by mechanical stimulus, manifests the highest phosphorescence efficiency of 4.56 % upon photoirradiation. During the grinding process, three different triboluminescent spectra were identified. Upon introduction of a mechanical stimulus, the triboluminescence emission is cyan, whereas after an extended period it changed to blue. After removing the mechanical stimulus, green-white phosphorescent emission was observed. Careful research on single-crystal structures and theoretical calculations demonstrate that strong Br⋅⋅⋅Br interactions are vital to facilitate spin-orbit coupling and promote intersystem crossing, thus generating the unique properties.