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Organic emitters that exhibit room‐temperature phosphorescence (RTP) in neat films have application potential for optoelectronic devices, bio‐imaging, and sensing. Due to molecular vibrations or rotations, the majority of triplet excitons recombine rapidly via non‐radiative processes in purely organic emitters, making it challenging to observe RTP in amorphous films. Here, a chemical strategy to enhance RTP in amorphous neat films is reported, by utilizing through‐space charge‐transfer (TSCT) effect induced by intramolecular steric hindrance. The donor and acceptor groups interact via spatial orbital overlaps, while molecular motions are suppressed simultaneously. As a result, triplets generated under photo‐excitation are stabilized in amorphous films, contributing to phosphorescence even at room temperature. The solvatochromic effect on the steady‐state and transient photoluminescence reveals the charge‐transfer feature of involved excited states, while the TSCT effect is further experimentally resolved by femtosecond transient absorption spectroscopy. The designed luminescent materials with pronounced TSCT effect show RTP in amorphous films, with lifetimes up to ≈40 ms, comparable to that in a rigid polymer host. Photoluminescence afterglow longer than 3 s is observed in neat films at room temperature. Therefore, it is demonstrated that utilizing intramolecular steric hindrance to stabilize long‐lived triplets leads to phosphorescence in amorphous films at room temperature. [ABSTRACT FROM AUTHOR]

Aiming to design new efficient organic triplet emitters, here a new electron‐accepting moiety 11,13‐dihydro‐12H‐dibenzo[a,c]imidazo[4,5‐i]phenazin‐12‐one (BIPO) are reported. Three new BIPO derivatives containing long alkyl chains, namely DBIPO (acceptor only), DBIPOBr (acceptor containing bromine atoms), and DBIPOAc with acridan moieties in a donor‐acceptor‐donor configuration, are designed and investigated. Efficient room temperature phosphorescence (RTP) is detected for the three compounds, stemming from a high‐lying (anti‐Kasha type) triplet emission occurring in the acceptor moiety. Additionally, the tetrahydrofuran‐ and dichloromethane DBIPOAc solutions show (i) a dual‐band photoluminescence profile stemming from anti‐Kasha emissions from high‐lying charge‐transfer (1CT) and locally excited (1LE) states, and (ii) a thermally activated delayed fluorescence (TADF) from the same high‐lying 1CT state. Importantly, DBIPOAc doped in rigid nonpolar polymer Zeonex simultaneously exhibits both TADF and RTP, with the emission quantum yield reaching 69.6%. Due to these properties, the BIPO derivatives constitute promising candidates as multi‐functional new emitters for the preparation of active layers of electroluminescent devices and optical oxygen/pressure sensors. The reasons for these interesting properties are discussed in detail. [ABSTRACT FROM AUTHOR]

Organic afterglow can be generated from persistent thermally activated delayed fluorescence (pTADF) or organic ultralong room temperature phosphorescence (OURTP), but the pTADF plus OURTP type organic afterglow is challenging to achieve, especially for the color‐tunable and high‐temperature ones. Herein, an accessible strategy toward such dual‐mode afterglow is presented by doping the indolo[3,2‐b]carbazole (ICZ‐p1) into polymethyl methacrylate (PMMA). The resulting films exhibit photo‐activated afterglow with two persistent emission peaks of ca. 435 and 497 nm. Impressively, their longest lifetimes respectively reach to 2.28 and 2.47 s at 298 K, along with 0.32 and 0.42 s at 360 K, enabling the afterglow at room and high temperature. Experimental and theoretical results reveal that the photo‐activated afterglow is associated with the elimination of molecular O2 inside film and composed by the pTADF with multi‐resonance (MR) effect and OURTP. By altering the temperature from 77 to 358 K, the color‐tunable afterglows of green and blue are harvested at such temperature ranges. Benefiting from the multi‐resonance thermally activated delayed fluorescence (MRTADF) characteristics, this emitter can release narrow‐band electroluminescence. Consequently, the results obtained here may offer important references for chasing MRTADF plus OURTP‐type dual‐mode organic afterglow showing color‐tunable and high‐temperature features. [ABSTRACT FROM AUTHOR]

Room temperature phosphorescence rarely occurs from pure organic molecules, especially in the solid‐state. A strategy for the design of highly emissive organic phosphors is still hard to predict, thus impeding the development of new functional materials with the desired optical properties. Herein, we analyze a family of alkyl and aryl‐substituted persulfurated benzenes, the latter representing a class of organic solid‐state triplet emitters able to show very high emission quantum yield at room temperature. In this work, we correlate structural parameters with the photophysical properties observed in different experimental conditions (diluted solution, crystalline and amorphous phase at RT and low temperature). Our results, corroborated by a detailed computational analysis, indicate a close relationship between the luminescence properties and i) the nature of the substituents on the persulfurated core, ii) the adopted conformations in the solid state, both in crystalline and amorphous phases. These factors contribute to characterize the lowest‐energy lying excited‐state, its deactivation pathways, the phosphorescence lifetime and quantum yield. These findings provide a useful roadmap for the development of highly performing purely organic solid‐state emitters based on the persulfurated benzene platform. [ABSTRACT FROM AUTHOR]

Supramolecular organic framework (SOF) has recently garnered significant research interest in the field of luminescent materials. However, SOF with room‐temperature phosphorescence emission in solution is very rare due to the quenching of dissolved oxygen and free molecular motions, which would lead to nonradiative deactivation of triplet exciton in liquid state. In this work, a 3D cationic phosphorescent SOF is synthesized through host‐guest interaction between CB[8] and a tetrahedral monomer TBBP, which can rapidly adsorb anionic guests in solution. When anionic dyes are introduced, triplet to singlet Förster resonance energy transfer (TS‐FRET) in solution can be achieved, and delayed fluorescence with large Stokes shift can be realized. Additionally, when anionic drugs are introduced, the phosphorescence of TBBP‐CB[8] can be quenched due to charge transfer, enabling the detection of drugs through phosphorescence signals. Taking advantage of the fast adsorption property of 3D SOF, an INHIBIT logic gate with three inputs and two outputs is constructed. These findings provide a novel method to prepare phosphorescent functional materials and a new pathway to construct TS‐FRET system in solution. [ABSTRACT FROM AUTHOR]

Organic scintillators have recently gained considerable attentions in X‐ray detection for their potential applications in biomedical radiograph and security inspection. However, the weak X‐ray absorption and/or inefficient exciton utilization have limited the development and commercialization of organic scintillators. Currently, high‐performance X‐ray organic scintillators are scarce and organic scintillators with dual triplet‐harvesting channels have not been explored before. Here, we develop several proof‐of‐concept sulfone‐based organic molecules, C1–C7, using different alkoxy chains to manipulate molecular packing mode. These materials exhibit dual triplet‐harvesting channels of thermally activated delayed fluorescence (TADF) and room‐temperature phosphorescence (RTP) in aggregated state. Inspiringly, these molecules display distinct radioluminescence under the X‐ray stimulation. Among them, C6 behaves the highest light yield of 16,558 photons MeV−1. Moreover, clear X‐ray images are demonstrated in both aggregated state and single‐molecule level. High spatial resolutions of 15.0 and 10.6 line pairs per millimeter (lp mm−1) are achieved for rigid and flexible scintillator screens, exceeding most reported organic and conventional inorganic scintillators. These results highlight the great potential of organic molecules with TADF and RTP nature for efficient X‐ray scintillation and imaging. [ABSTRACT FROM AUTHOR]

In purely organic room‐temperature phosphorescence (RTP) materials, fluorescence radiative transitions generally compete against inter‐system crossing (ISC) transitions to give fluorescence/phosphorescence dual emission. In order to achieve pure phosphorescence in RTP organic light‐emitting diodes (OLEDs), extended π‐conjugation is introduced into Se‐containing donors to suppress the fluorescence radiative transitions by the symmetry excited state orbitals in the introduced π–π* transitions that cancel the overlap of the orbitals, and two novel nonaromatic amine donor containing orange RTP emitters namely 2‐(benzo[c]phenoxaselenin‐10‐yl)‐4,6‐diphenyl‐1,3,5‐triazine (BPXSeDRZ) and 2‐(dibenzo[a,c]phenoxaselenin‐11‐yl)‐4,6‐diphenyl‐1,3,5‐triazine (DBPXSeDRZ) are developed, both of which exhibit efficient orange pure phosphorescence in doped films thanks to the sufficient ISC transitions. As a result, high external quantum efficiencies of 17.2% and 17.9% are respectively achieved for the orange RTP‐OLEDs based on BPXSeDRZ and DBPXSeDRZ for the first time, and they also exhibit stable pure electro‐phosphorescence spectra in a wide driving voltage. Moreover, by adopting DBPXSeDRZ as a sensitizer to harvest the triplet excitons and tetraphenyldibenzoperiflanthene as a conventional fluorescent emitter, the external quantum efficiency of the sensitized red fluorescent OLED can be elevated to 10.1%, which greatly expands the potential applications of the metal‐free phosphors in OLEDs. [ABSTRACT FROM AUTHOR]

Tautomers coexisting in an equilibrium system have significant potential for regulating luminescent properties because of their structural differences. However, separating and stabilizing tautomers at room temperature is a considerable challenge. In this study, it is found that hydrogen‐bonded organic frameworks (HOFs) composed of Br‐ anions can effectively separate and stabilize two proton‐transfer tautomers of triarylformamidinium bromide: namely, the nitrogen cation (BA‐N) and carbon cation (BA‐C). The BA‐N crystal consisting of a dense anionic HOF and parallelly aligned organic cations exhibits green thermally activated delayed fluorescence and red room‐temperature phosphorescence (RTP). The BA‐C crystal contains acetone molecules that induce an antiparallel arrangement of the organic cations to form a loose HOF, producing blue prompt fluorescence and green RTP. Interestingly, switching of the HOFs between BA‐N and BA‐C can be achieved through the uptake and release of acetone, thereby dynamically adjusting multiple luminescent properties. Consequently, the HOF crystals can be used for the highly sensitive and specific sensing of acetone with a detection limit of 66.74 ppm. This study not only stabilizes tautomeric luminescent materials at room temperature, but also provides a new method for constructing smart HOFs with a sensitive response to a stimulus. [ABSTRACT FROM AUTHOR]

Research of thermally activated delayed fluorescence (TADF) and room‐temperature phosphorescence (RTP) materials is attractive owing to their extensive applications in various fields. However, achieving organic TADF and RTP materials, particularly those with stimulus‐responsiveness and tunability, is highly desirable but challenging and rarely reported. Herein, two easily synthesized organic molecules are reported with abnormal stimulus‐responsive switchable TADF and RTP effects, in which phenothiazine (PTZ) and benzo[b]phenothiazine (BPTZ) based donor−acceptor molecules PTZ‐DBQ and BPTZ‐DBQ show mechanical‐induced TADF in crystalline phase and photo‐responsive RTP in doping poly(methyl methacrylate) (PMMA) films. This is the first time tetracyclic BPTZ has been used as a donor in achieving TADF and RTP materials, and it is found that BPTZ‐DBQ exhibits remarkably better photophysical properties than PTZ‐DBQ. Systematic studies of experimental results and theoretical calculations indicate that the conformational heterogeneity plays an essential role in achieving mechanical‐induced TADF with mechanochromic luminescence (MCL) property. Embedding the organic phosphors into rigid polymer matrices effectively suppresses the molecular motion, thus turning on the RTP emission channel. The conversion of 3O2 to 1O2 under UV irradiation is mainly responsible for the photo‐induced process. These multifunctional luminescent materials have great potential applications in chemical sensors, information encryption, and anti‐counterfeiting. [ABSTRACT FROM AUTHOR]

The understanding of the excited state dynamics of thermally activated delayed fluorescence (TADF) materials is crucial. In this study, two donor–acceptor‐type TADF emitters with highly twisted conformation are synthesized. The emitters with subtle chemical modification of donor unit exhibit opposite aggregation luminescent behaviors: aggregation‐induced emission (AIE) and aggregation‐caused quenching (ACQ). Through the photophysical properties study, crystallographic analysis, and theory simulations, it is discovered that X‐aggregation supports AIE behavior by restricting the intramolecular motions and preserving TADF emission via an efficient reverse intersystem crossing (RISC) process, but on the other hand, H‐aggregation leads to ACQ behavior due to inhibited RISC, disabled TADF channel, and weak phosphorescence from radiative low‐lying triplet state. The findings shed light on the excited‐state dynamic behaviors of TADF emitters, which are dependent on aggregation. [ABSTRACT FROM AUTHOR]

Inorganic boric acid (BA) is generally not considered an efficient afterglow material, and several groups have reported its extremely weak room‐temperature phosphorescence (RTP) in the blue spectral region. It is discovered that heat treatment of BA results in increased afterglow intensity (27‐fold increase) and prolonged emission lifetime (from 0.83 to 1.59 s), attributed to enhanced through‐space conjugation (TSC) of BA. The afterglow intensity of BA can be increased further (≈415 folds) by introducing p‐hydroxybenzoic acid (PHA), which contains a conjugated molecular motif, to further promote the TSC of the BA system. This combination results in the production of afterglow materials with a photoluminescence quantum yield of 83.8% and an emission lifetime of 2.01 s. In addition, a tunable multicolor afterglow in the 420–490 nm range is achieved owing to the enhancement of the RTP and thermally activated delayed fluorescence of PHA, where BA exerts a confinement effect on the guest molecules. Thus, this study demonstrates promising afterglow materials produced from extremely abundant and simple precursor materials for various applications. [ABSTRACT FROM AUTHOR]

The excited‐state tuning of luminescent metal–organic compounds has made great progress in the fields of optical imaging, photocatalysis, photodynamic therapy, light‐emitting devices, sensors, and so on. Although metal–organic compounds with high luminescence efficiency can be realized via enhanced molecular rigidity and heavy‐atom effect, their corresponding luminescence lifetimes are still limited on the order of a nanosecond to a millisecond, owing to the inherent competition between luminous efficiency and lifetime. Therefore, the advanced applications (i.e., persistent afterglow imaging, information security, anti‐counterfeiting, and smart materials, among others) related with long persistent luminescence (LPL, typically with the excited‐state lifetime larger than millisecond) are seriously hindered. This review gives a timely and systematic summary of metal–organic compounds for realizing room‐temperature phosphorescence (RTP)‐type and thermally activated delayed fluorescence (TADF)‐type LPL during last few years. Particularly, based on the perspectives of time, space, and energy dimensions, fundamental materials design and coordination assembly are systematically described for the first time. Moreover, the internal and external factors of influencing the LPL properties in terms of luminescence efficiency, lifetime, and color are illustrated. Last but not least, perspectives and challenges are also discussed for developing LPL from metal–organic compounds. [ABSTRACT FROM AUTHOR]

Responsive luminescence materials with prolonged lifetime and multicolor emission have drawn great attention due to their attractive optical property and potential applications. Herein, two responsive carbon dots (CDs) based composites: CD1@MCM-22P and CD2@ZSM-12 were achieved by a one-step hydrothermal method. By adjusting the hydrothermal condition, CD1@MCM-22P owns temperature-dependent afterglow, while CD2@ZSM-12 is equipped with excitation-dependent room-temperature phosphorescence. The photoluminescence mechanisms of CD1@MCM-22P and CD2@ZSM-12 were investigated and proposed, and the composites were applied in multi-mode anti-counterfeiting. This work provides an insight as well as a feasible method for the development of multi-emissive CDs@zeolite composite. [ABSTRACT FROM AUTHOR]

Purely organic room‐temperature phosphorescence (RTP) materials generally exhibit low phosphorescence quantum yield (ϕP) and long phosphorescence lifetime (τP) due to the theoretically spin‐forbidden triplet state. Herein, by introducing a donor–acceptor (D–A) skeleton with a phenoxaselenine donor, three nonaromatic amine donor containing compounds with high ϕP and short τP in amorphous films are developed. Besides the enhanced spin–orbit coupling (SOC) by the heavy‐atom effect of selenium, the D–A skeleton which facilitates orbital angular momentum change can further boost SOC, and severe nonradiative energy dissipation is also suppressed by the rigid molecular structure. Consequently, a record‐high external quantum efficiency of 19.5% are achieved for the RTP organic light‐emitting diode (OLED) based on 2‐(phenoxaselenin‐3‐yl)‐4,6‐diphenyl‐1,3,5‐triazine (PXSeDRZ). Moreover, voltage‐dependent color‐tunable emission and single‐molecule white emission are also realized. These results shed light on the broad prospects of purely organic phosphorescence materials as highly efficient OLED emitters especially for potential charming lighting applications. [ABSTRACT FROM AUTHOR]

Three donor‐acceptor compounds based on the imidazo‐pyrazine‐5,6‐dicarbonitrile (IPDC) acceptor were synthesized. The IPDC emitters exhibit blue to near‐infrared (NIR) emission with up to 54 % photoluminescent quantum yield. 9,9‐Dimethyl‐9,10‐dihydroacridine (ACR), phenoxazine (POX), and phenothiazine (PTZ) served as electron donors. IPDC‐POX displayed NIR emission in toluene solution, while showing room‐temperature phosphorescence in the solid state. IPDC‐ACR exhibited yellow thermally activated delayed fluorescence. Interestingly, dual‐emissive behavior as well as excitation‐dependent thermally activated delayed fluorescence (TADF) was found for IPDC‐PTZ, arising from the two conformers of phenothiazine derivatives. Overall, this work describes a novel strong electron acceptor from the fusion of imidazole, pyrazine, and nitrile functional groups into one conjugated heterocycle for materials exhibiting NIR emission, TADF, and/or room‐temperature phosphorescence (RTP). [ABSTRACT FROM AUTHOR]

Despite vast applications of macrocycles in supramolecular chemistry, achieving long‐lived emissions including room‐temperature phosphorescence (RTP) or thermally activated delayed fluorescence (TADF) for potential use still presents a great challenge. This work first reports hydrogen‐bonded (H‐bonded) macrocycles emitting RTP and TADF by introducing various donors onto the same aramide skeleton containing a rigid acceptor. The formation of charge transfer effectively enhances the photoluminescence efficiency. Aromatic carbonyl groups promote the intersystem crossing. The drastically reduced flexibility of chromophores fixed by the H‐bonded macrocyclic framework contributes to suppress the nonradiative decay to stabilize triplet excitons. Therefore, RTP and TADF are acquired by altering donors, and are systematically revealed by comparisons with control compounds and theoretical calculations. Finally, near white‐light emission (CIE, 0.30, 0.33) is realized via host–guest interactions. [ABSTRACT FROM AUTHOR]

Organic room‐temperature phosphorescent (RTP) materials routinely incorporate polymeric components, which usually act as non‐functional or "inert" media to protect excited‐state phosphors from thermal and collisional quenching, but are lesser explored for other influences. Here, we report some exemplary "active roles" of polymer matrices played in organic RTP materials, including: 1) color modulation of total delayed emissions via balancing the population ratio between thermally‐activated delayed fluorescence (TADF) and RTP due to dielectric‐dependent intersystem crossing; 2) altered air sensitivity of RTP materials by generating various surface morphologies such as nano‐sized granules; 3) enhanced bacterial elimination for enhanced electrostatic interactions with negatively charged bio‐membranes. These active roles demonstrated that the vast library of polymeric structures and functionalities can be married to organic phosphors to broaden new application horizons for RTP materials. [ABSTRACT FROM AUTHOR]

Clusterization‐triggered emission is emerging as a powerful strategy leading to useful luminescence such as room‐temperature phosphoresce (CTE‐RTP), yet people's recognition on CTE‐RTP is still very limited, so that it remains challenging to achieve multicolor CTE‐RTP due to the difficulty in tailoring the clustering state of the atoms with lone pair electrons. The authors report that phosphorescence resonance energy transfer (PRET) can occur in the CTE‐RTP system, which enables fine‐tuning the color of the CTE‐RTP. Since the CTE‐RTP is a broad band in the range of 400–700 nm, and the dipole orientations are diverse in the CTE material, PRET can always occur between the CTE‐RTP and arbitrary fluorescent dyes to obtain delayed fluorescence ranging from green to near infrared. Because the lifetime of the delayed fluorescence depends on their molecular structure, dynamic afterglow can be facilely achieved in the ensemble of a PRET‐CTE‐RTP system, making it very appealing in anticounterfeiting. [ABSTRACT FROM AUTHOR]

Room-temperature phosphorescence carbon dots (CDs) show the highlighted advantages in chemical sensing and bioimaging owing to its long lifetime, however, acquiring the efficient phosphorescence of carbon dots is still encountering difficulty due to the spin prohibition. Here, we synthesized one type of CDs through one-step hydrothermal method. To be specific, the CDs displayed the blue fluorescence in aqueous, and emitted the bright green phosphorescence when being coated on the filter paper. Importantly, introducing coumarin to the CDs resulted in the distinct quenching of both its fluorescence and phosphorescence. Based on this phenomenon, we successfully established a dual-channel detection of coumarin. The fluorescence detection channel exhibited a linear range of 5–350 μM with a detection limit of 0.196 μM, while the phosphorescence detection channel achieved a linear range of 50–1000 μM with a detection limit of 0.268 μM. The further investigation revealed that IFE and SQE were mainly responsible for the fluorescence quenching of CDs, while the phosphorescence quenching was originated from the increased energy gap between the singlet and triplet states (ΔE ST) of CDs, thus obstructing the ISC process. Moreover, we employed the CDs as the phosphorescent ink for anti-counterfeiting. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Tris(6-methyl-2-pyridyl)phosphine (L) reacts with Cu(I) halides to afford two neutral [Cu 2 Cl 2 L 2 ], [Cu 4 I 4 L 2 ] and two zwitterionic complexes [Cu 4 Hal 4 L 2 (MeCN) 2 ] (Hal = Br and I). • The structure of the obtained complexes is discussed. • The presented complexes emit phosphorescence at ambient temperature. A series of luminescent Cu(I) complexes has been synthesized by the reactions between tris(6-methyl-2-pyridyl)phosphine (L) and Cu(I) halides. The reaction of L with CuCl in CH 2 Cl 2 forms a binuclear complex [Cu 2 Cl 2 L 2 ], while CuI under the same conditions unexpectedly affords the tetranuclear neutral [Cu 4 I 4 L 2 ] complex. At the same time, the interaction of CuBr or CuI with L in MeCN medium unexpectedly gives rare co-called «All-in-One» complexes [Cu 4 Hal 4 L 2 (MeCN) 2 ] (Hal = Br and I). At ambient temperature, the above compounds display a solid-state luminescence (λ max = 535–565 nm) with emission lifetimes of 1.8–6.9 μs, and the quantum efficiency of up to 80 %. [ABSTRACT FROM AUTHOR]

The construction of highly luminescent solid‐state materials with long‐lived afterglow through a straightforward method is promising but still a challenging task. Herein, a heat‐treatment strategy is proposed to embed levofloxacin (Lev) in the matrix of boric acid (BA) to produce a complex with a photoluminescence quantum yield of 63.8% and an emission lifetime of 0.74 s (afterglow: >5 s). Detailed investigations suggest that the unique photophysical properties of the complex are attributed to the confinement effect of BA matrix to Lev, which reduces the probability of nonradiative relaxation and activates the radiative decays to result in the promoted emission efficiency. In addition, thermally activated delayed fluorescence is also activated due to the alteration of the π transition of Lev by the formation of boron–carbon bonds. The emission color and lifetime are also modulated through controlling the synthetic conditions, which endow their applications both in light‐emitting diodes and information encryption. Thus, the present results are significant for the construction of solid‐state luminescent materials, including fluorescence and room‐temperature phosphorescence, and also provide a solid and universal theory to clarify their detailed emission profiles. [ABSTRACT FROM AUTHOR]

A purely organic supramolecular assembly emitting three‐photon room‐temperature phosphorescence (RTP) is constructed from a macrocyclic host, cucurbit[8]uril (CB[8]), and 4‐bromophenyl pyridine salt having an alkyl chain length of 6 or 12 carbon atoms (6C and 12C, respectively). Benefiting from macrocyclic host confined guests, the encapsulation of 12C and 6C in the CB[8] cavity results in three‐photon absorption and subsequent near‐infrared (NIR) phosphorescence emission. Notably, secondary assembly with sulfonated β‐cyclodextrin (SCD) further enhances the phosphorescence emission of the multilevel supramolecular assembly. NIR‐delayed fluorescence via a light‐harvesting phosphorescent energy transfer system is achieved by adding Nile blue as a substrate. Comparison of 12C/CB[8]/SCD and 6C/CB[8]/SCD shows that a long hydrophobic layer is more conducive to stabilizing NIR‐delayed fluorescence emission. These findings indicate that multilevel supramolecular assemblies can be used for three‐photon‐excited NIR‐delayed fluorescence and RTP imaging of cancer cells, which greatly expands the biological applications of pure organic RTP materials. [ABSTRACT FROM AUTHOR]

Highly efficient organic thermally activated delayed fluorescence (TADF) and room‐temperature phosphorescence (RTP) emitters for organic light‐emitting diodes (OLEDs) generally consist of a twisted donor–acceptor skeleton with aromatic amine donors. Herein, through introducing sulfur atoms into isomeric pentaphene and pentacene frameworks, we demonstrate a set of polycyclic luminophores exhibiting efficient TADF and RTP characters. The incorporation of sulfur atoms confirms a folded molecular plane, while intensifies singlet–triplet spin‐orbit coupling. Further, the isomeric effect has a significant effect on the electronic structure of excited state, giving rise to the investigated compounds tunable luminescence mechanisms of TADF and RTP. With efficient triplet harvesting ability, maximum external quantum efficiencies up to 25.1 % and 8.7 % are achieved for the corresponding TADF and RTP OLEDs, verifying the great potential of sulfur‐bridged frameworks for highly efficient devices. [ABSTRACT FROM AUTHOR]

Metal‐free organic triplet emitters are an emerging class of organic semiconducting material. Among them, molecules with tunable emission responsive to environmental stimuli have shown great potential in solid‐state lighting, sensors, and anti‐counterfeiting systems. Here, a novel excited‐state intramolecular proton transfer (ESIPT) system is proposed showing the activation of thermally activated delayed fluorescence (TADF) or room‐temperature phosphorescence (RTP) simultaneously from both keto and enol tautomers. The prototype ESIPT triplet emitters exhibit up to 50% delayed emission quantum yield. Their enol–keto tautomerization can be switched by controlling the matrix acidity in doped polymer films. Taking advantage of these unique properties, "on‐off" switchable triplet emission systems controlled by acid vapor annealing, as well as photopatterning systems capable of generating facile and high‐contrast emissive patterns, are devised. [ABSTRACT FROM AUTHOR]

Although bowl‐shaped N‐pyrrolic polycyclic aromatic hydrocarbons (PAHs) can achieve excellent electron‐donating ability, their application for optoelectronics is hampered by typically low photoluminescence quantum yields (PLQYs). To address this issue, we report the synthesis and characterization of a series of curved and fully conjugated nitrogen‐doped PAHs. Through structural modifications to the electron‐accepting moiety, we are able to switch the mechanism of luminescence between thermally activated delayed fluorescence (TADF) and room‐temperature phosphorescence (RTP), and to tune the overall PLQY in the range from 9 % to 86 %. As a proof of concept, we constructed solid‐state organic light‐emitting diode (OLED) devices, which has not been explored to date in the context of concave N‐doped systems being TADF/RTP emitters. The best‐performing dye, possessing a peripheral trifluoromethyl group adjacent to the phenazine acceptor, exhibits yellow to orange emission with a maximum external quantum efficiency (EQE) of 12 %, which is the highest EQE in a curved D‐A embedded N‐PAH to date. [ABSTRACT FROM AUTHOR]

Persistent luminescence has attracted great attention due to the unique applications in molecular imaging, photodynamic therapy, and information storage, among many others. However, tuning the dynamic persistent luminescence through molecular design and materials engineering remains a challenge. In this work, the first example of excitation‐dependent persistent luminescence in a reverse mode for smart optical materials through tailoring the excited‐state proton transfer process of metal cytosine halide hybrids is reported. This approach enables ultralong phosphorescence and thermally activated delayed fluorescence emission colors highly tuned by modulation of excitation wavelength, time evolution, and temperature, which realize multi‐mode dynamic color adjustment from green to blue or cyan to yellow‐green. At the single crystal level, the 2D excitation/space/time‐resolved optical waveguides with triple color conversion have been constructed on the organic‐metal halide microsheets, which represent a new strategy for multi‐dimensional information encryption and optical logic gate applications. [ABSTRACT FROM AUTHOR]

Near‐infrared (NIR) luminescent materials have received considerable attention owing to their intriguing applications in fields such as high‐resolution biological imaging and information technology. In this context, room‐temperature phosphorescence (RTP) materials with emission bands in the NIR region are rare. Metal‐free arylselanyl‐BODIPY triplet photosensitizers were doped into a benzophenone (BP) matrix. When excited at 350 nm, RTP emission was observed in the NIR region with λem values of 750–816 nm, and the phosphorescence quantum yield was up to 0.48 %. The detection of an extremely large Stokes shift (≥400 nm) was responsible for the triplet‐triplet energy transfer from BP to the BODIPY guest. Furthermore, the RTP properties were tuned by derivatization of the selenium‐containing BODIPY guests. NIR‐RTP properties were also detected upon excitation at 470 nm with a persistent lifetime of up to 17.5 ms. Notably, in addition to NIR RTP emission, thermally activated delayed fluorescence was detected at 620 nm when 10 ms delayed spectra were measured for the MeOSeBOD‐doped system. Considering the synthetic versatility of the BODIPY chromophore, this work opens up a new strategy for developing small molecule‐based NIR RTP systems. [ABSTRACT FROM AUTHOR]

Despite ongoing research into photocontrolled supramolecular switches, reversible photoswitching between room-temperature phosphorescence (RTP) and delayed fluorescence is rare in the aqueous phase. Herein, an efficient RTP-fluorescence switch based on a cascaded supramolecular assembly is reported, which is constructed using a 6-bromoisoquinoline derivative (G3), cucurbit[7]uril (CB[7]), sulfonatocalix[4]arene (SC4A4), and a photochromic spiropyran (SP) derivative. Benefiting from the confinement effect of CB[7], initial complexation with CB[7] arouses an emerging RTP signal at 540 nm for G3. This structure subsequently coassembles with amphiphilic SC4A4 to form tight spherical nanoparticles, thereby further facilitating RTP emission (-12 times) in addition to a prolonged lifetime (i.e., 1.80 ms c.f., 50.1 µs). Interestingly, following cascaded assembly with a photocontrolled energy acceptor (i.e., SP), the efficient light-driven RTP energy transfer occurs when SP is transformed to its fluorescent merocyanine (MC) state. Ultimately, this endows the final system with an excellent RTP-fluorescence photoswitching property accompanied by multicolor tunable long-lived emission. Moreover, this switching process can be reversibly modulated over multiple cycles under alternating UV and visible photoirradiation. Finally, the prepared switch is successfully applied to photocontrolled multicolor cell labeling to offer a new approach for the design and fabrication of novel advanced light-responsive RTP materials in aqueous environments. [ABSTRACT FROM AUTHOR]

The organic solid-state light-emitting materials have attracted more and more attention owing to their promising applications in displays, lasers and optical communications. In contrast to isolated molecule, there are various weak intermolecular interactions in organic solids that sometimes have a large impact on the excited-state properties and energy dissipation pathways, resulting in strong fluorescence/phosphorescence. It is increasingly necessary to reveal the luminescence mechanism of organic solids. Here, we briefly review how intermolecular interactions induce strong normal fluorescence, thermally activate delayed fluorescence and room-temperature phosphorescence in organic solids by examining changes in geometry, electronic structures, electron-vibration coupling and energy dissipation dynamics of the excited states from isolated to aggregated molecules. We hope that the review will contribute to an in-depth understanding of the excited state properties of organic solids and to the design of excellent solid-state light-emitting materials. [ABSTRACT FROM AUTHOR]

Organic room‐temperature phosphors with high performances are of great importance for broad range of potential applications. Herein, a new concept of cage effect is proposed to effectively promote room‐temperature phosphorescence (RTP) property of organic materials. A novel phosphor, bearing electron‐donating carbazole and electron‐accepting boronate ester moieties (CBBU) is designed and synthesized. CBBU crystals show multiple photoluminescence including concomitant fluorescence, thermally activated delayed fluorescence (TADF), and RTP. Further doping CBBU in boronate ester crystals (DB/CBBU) boosts remarkably deep‐blue RTP emission with CIE coordinates (0.15, 0.09) and a lifetime of 3.69 s, which is longer by four orders of magnitude than that of neat CBBU crystals. To the best of knowledge, it is the longest deep‐blue organic RTP materials reported so far. To understand this phenomenon, cage effect in terms of bending, twisting, and crowding degrees, as well as interaction of chromophores with cages has been taken into consideration. The results demonstrate that the strong cage effect alleviates effectively molecular motion of chromophores and then promotes simultaneously their RTP efficiency and lifetime. Similar results have also been found in a series of boronate ester derivatives. Furthermore, applications of the efficient RTP materials for temperature measurements, thermal transition detection, and UV sensing are exploited. [ABSTRACT FROM AUTHOR]

The spin-forbidden nature of triplet exciton transitions is a limitation for achieving a carbon dots-based material with room-temperature phosphorescence (RTP). Here, fluorine-nitrogen co-doped carbon dots (FNCDs), prepared using the solvothermal method and further gas-phase fluorination from fructose and diethylenetriamine (DETA), were found to exhibit RTP lifetime and quantum yield of 1.14 s and 8.3%. By comparing the structure and performance of the nitrogen-doped carbon dots (NCDs) and FNCDs, it was found that the RTP of FNCDs originates from the π→π∗ and n→π∗ electron transitions C–N/C N, which can be attributed to the small energy gap between the singlet and triplet states. We further explored the mechanism of RTP by analyzing the hydrogen bonding between carbon dots and polyvinyl alcohol matrix. The semi-ionic C–F bonds also enhance intramolecular and intermolecular hydrogen bonding and reduce the quenching of RTP without the oxygen barrier. Furthermore, we applied the prepared aqueous FNCDs as an advanced security ink for information printing and anti-counterfeiting. The effective conversion of fluorescence to room temperature phosphorescent carbon dots is achieved by fluorinating NCDs to enhance intersystem crossing and stabilize the triplet-excited states. The NCD and FNCD aqueous solutions made into advanced anti-counterfeiting inks have the prospect of being used in information printing and anti-counterfeiting. [Display omitted] [ABSTRACT FROM AUTHOR]

Control of excited‐state dynamics is key in tuning room‐temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF) emissions but is challenging for organic luminescent materials (OLMs). We show the regulation of TADF and RTP emissions of a boron difluoride β‐acetylnaphthalene chelate (βCBF2) by controlling the excited‐state dynamics via its J‐ and H‐aggregation states. Two crystalline polymorphs emitting green and red light have been controllably obtained. Although both monoclinic, the green and red crystals are dominated by J‐ and H‐aggregation, respectively, owing to different molecular packing arrangements. J‐aggregation significantly reduces the energy gap between the lowest singlet and triplet excited states for ultra‐fast reverse intersystem crossing (RISC) and enhances the radiative singlet decay, together leading to TADF. The H‐aggregation accelerates the ISC and suppresses the radiative singlet decay, helping to stabilize the triplet exciton for RTP. [ABSTRACT FROM AUTHOR]

Aggregation‐induced emission (AIE), thermally activated delayed fluorescence (TADF), room‐temperature phosphorescence (RTP), and mechanoluminescence (ML) have attracted widespread interest. However, a multifunctional organic emitter exhibiting simultaneous AIE, TADF, RTP, and ML has not been reported. Now, two multifunctional blue emitters with very simple structures, mono‐DMACDPS and Me‐DMACDPS, exhibit typical AIE, TADF, and RTP properties but different behavior in mechanoluminescence. Crystal structure analysis reveals that large dipole moment and multiple intermolecular interactions with tight packing mode endow mono‐DMACDPS with strong ML. Combined with the data of crystal analysis and theoretical calculation, the separated monomer and dimer in the crystal lead to the typical TADF and RTP properties, respectively. Simple‐structure mono‐DMACDPS is the first example realizing TADF, RTP, AIE, and ML simultaneously. [ABSTRACT FROM AUTHOR]

A D‐A‐D′ type pure organic molecule, named ODFRCZ, has unique triple‐emission character covering fluorescence, phosphorescence, and delayed fluorescence (DF). The phosphorescence of ODFRCZ has a rather long lifetime of about 350 ms at room temperature. One dimer of ODFRCZ with enhanced parallel molecular packing acts more effectively to prompt ISC processes, which further generates room‐temperature phosphorescence (RTP), owing to the larger transition dipole moment and closer energy level between S1 and Tn. ODFRCZ is a rare example of an organic RTP molecule that shows dual‐stimuli responsiveness of dual‐mode mechanochromism (fluorescence red‐shift and RTP/DF on‐off switch) and reversible crystal‐state photochromism. This work may broaden the knowledge for stimuli‐responsive RTP organic molecules and lay the foundation for their wide‐scale applications. [ABSTRACT FROM AUTHOR]

The dehydrating cyclotrimerization of 1‐tetralone in the presence of titanium tetrachloride at high temperatures leads to homotruxene, a nonplanar arene in which the twist angles between its three outer benzene rings and the central benzene are stabilized by ethylene bridges. This non‐planar configuration allows for pronounced spin–orbit coupling and a high triplet energy, leading to room‐temperature phosphorescence in air with a lifetime of 0.38 s and a quantum yield of 5.6 %, clearly visible to the human eye after switching off the excitation. Triplet–triplet annihilation is found to simultaneously lead to a substantial delayed fluorescence, unprecedented from a pure hydrocarbon at ambient conditions, with a lifetime of 0.11 s. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two sets of isomeric TADF emitters are designed and synthesized. • The RTP efficiency and lifetime are regulated by tuning their energy levels and molecular packing modes through isomer and substituent engineering. • 4-CzAIAd displays the longest RTP lifetime of 301 ms. Metal-free organic phosphorescent materials are crucial for the advancement of optoelectronics and bioelectronics. Nonetheless, achieving rational control over the performance of room-temperature phosphorescence (RTP) presents a significant challenge. In this study, two sets of isomeric thermally activated delayed fluorescence (TADF) emitters with a donor–acceptor (D-A) configuration are designed and synthesized. Their RTP efficiency and lifetime are regulated by tuning their energy levels and molecular packing modes through isomer and substituent engineering. All of these materials exhibited afterglow emission, with the exception of 4-CzAIPh. A comprehensive investigation was conducted on the packing modes in the crystalline state, which revealed that the three RTP materials possess strong π-π interactions and numerous intermolecular forces, providing stability to the long-lived triplet excitons of RTP. Especially, 4-CzAIAd demonstrated the fastest intersystem crossing rate, the smallest fractional free volume and relatively larger spin–orbit coupling between its singlet and triplet states, as well as between its triplet state and ground state, which explains its longest phosphorescence lifetime of 301 ms. [ABSTRACT FROM AUTHOR]

[Display omitted] • A one chromophore with multi-excited states strategy is proposed for the de novo design of single white-emitting polymers. • P(DMPAc-O-DBTDO) is developed based on a characteristic D-O-A geometry. • P(DMPAc-O-DBTDO) shows not only fluorescence and TADF from S 1 , but also RTP from T 1. • Solution-processed WOLEDs are realized with tunable CIE coordinates and CCT for different illumination requirements. Single white-emitting polymers (SWPs) based on multi-chromophores with different colors are believed to show a great potential in solution-processed white light-emitting diodes (WOLEDs). However, they suffer from the extremely low loadings (one ten thousandth to one thousandth) for long-wavelength chromophores when incorporated into SWPs. To solve this bottleneck, we newly propose a one chromophore with multi-excited states strategy for the de novo design of SWPs. By adopting acridine as the donor (D), dibenzothiophene-S,S-dioxide as the acceptor (A) and oxygen as the linker between D and A to constitute the central chromophore fragment, P(DMPAc-O-DBTDO) is successfully developed to possess not only fluorescence and thermally-activated delayed fluorescence from the lowest singlet state (S 1), but also room-temperature phosphorescence from the lowest triplet state (T 1). As a consequence, a very broad electroluminescence that covers the whole visible region from 400 to 750 nm is realized, leading to an efficient and stable white light with a peak power efficiency of 7.5 lm W−1 (9.5 cd A-1, 3.7%). Meanwhile, the Commission Internationale de l'Eclairage (CIE) coordinates and correlated color temperature (CCT) could be well tuned in a wide doping concentration window (15–100%) for different illumination requirements. [ABSTRACT FROM AUTHOR]

Due to the high photoluminescence quantum yield (PLQY) and multiple-colored emissions by adjusting their composition and structures, organic-inorganic hybrid metal halides (MHs) have become promising emitters for next-generation light emitting and displays. When separate inorganic metal halides by larger organic cations in crystals, multiple low-dimensional MHs (LDMHs) at the molecular level can be constructed. These LDMHs have been widely reported to exhibit excellent photoluminescence properties which stems from radiative recombination of self-trapped excitons (STEs). Recently, efficient triplet state emission including room-temperature phosphorescence (RTP) originated from organic cations triplet states is also demonstrated in LDMHs, opening a new field for the development of phosphorescence emitters. Herein, we summarize and discuss the new progress in triplet state emission in LDMHs for a better understanding the RTP development of LDMHs for their versatile display applications. [Display omitted] • Recent reports on efficient RTP in LDMHs. • The key to achieve efficient RTP in LDMHs. • The latest application of RTP of LDMH materials. [ABSTRACT FROM AUTHOR]

New derivatives of trifluoromethyl benzene and tert -butyl disubstituted acridan or phenothiazine were designed and obtained by single-step synthesis, i.e., by Buchwald-Hartwig cross-coupling reactions of 1,3-dibromo-5-(trifluoromethyl)benzene with 3,7-di-tert-butyldimethylacridan, or 3,7-di-tert-butyl-10H-phenothiazine. The advantages in high thermal and photophysical characteristics were utilized in exciplex emission based OLEDs. In the optimal case, device showed maximum current, power, and external quantum efficiencies of 27.4 cd/A, 28.6 lm/W and 7.6%, respectively. Taking into account that successful employment of acridan or phenothiazine derivatives as donors in exciplex-forming systems remains scarce, the proposed design of donor compounds in this work shows their potential for successful implementation in complex emissive systems of OLEDs. •Derivatives of trifluoromethyl benzene and tert -butyl disubstituted acridan or phenothiazine were synthesized.. •They exhibited thermally activated delayed fluorescence and exciplex forming properties. •The compounds also showed room-temperature phosphorescence. •Exciplex emission based OLEDs with external quantum efficiency reaching 7.6% were obtained. [ABSTRACT FROM AUTHOR]