Multi-resonance induced thermally activated delayed uorescent (MR-TADF) materials have shown great potential in high-e ciency and narrowband organic light-emitting diodes (OLEDs). However, obvious e ciency roll-off attributed to slow reverse intersystem crossing (RISC) process hinders MR-TADF materials from practical applications. Here, we report a heavy-atom incorporating emitter, namely BNSeSe, based on selenium-integrated boron-nitrogen skeleton, showing 100% photoluminescence quantum yield and the highest rate of RISC (k RISC ) of 2.0 × 10 6 s -1 among MR-TADF molecules. The corresponding OLEDs exhibit excellent external quantum e ciency (EQE) up to 36.8% and ultra-low roll-off character at high brightness (with very small roll-off values of 2.8% and 14.9% at 1000 cd m -2 and 10000 cd m -2 , respectively). Furthermore, the outstanding capability to harvest triplet excitons also enables BNSeSe to be a superior sensitizer for hyper uorescence (HF) device, which shows state-of-the-art performance with record high EQE of 40.5%, power e ciency (PE) beyond 200 lm W -1 and luminance close to 200000 cd m -2 . Full TextOrganic light-emitting diodes (OLEDs) with simultaneously high e ciency and narrowband emission become increasingly important for the demands on energy-saving and high-quality of displays. Thanks to the pioneer work by Hatakeyama et al., multi-resonance (MR) thermally activated delayed uorescent (TADF) emitters have emerged with the astonishing narrowband emission that could ful ll the requirements. 1,2 A high external quantum e ciency (EQE) up to 34% and electroluminescence (EL) with full width at half maximum (FWHM) of 18 nm demonstrated their great potential towards practical applications. 3 However, MR-TADF emitters usually possess long delay lifetime of several tens of microsecond, which usually leads to large e ciency roll-off at high brightness and thus impede their commercialization. [4][5][6][7][8][9][10]

Sensitive and rapid identification of illicit drugs in a non-contact mode remains a challenge for years. Here we report three film-based fluorescent sensors showing unprecedented sensitivity, selectivity, and response speed to the existence of six widely abused illicit drugs, including methamphetamine (MAPA), ecstasy, magu, caffeine, phenobarbital (PB), and ketamine in vapor phase. Importantly, for these drugs, the sensing can be successfully performed after 5.0 × 105, 4.0 × 105, 2.0 × 105, 1.0 × 105, 4.0 × 104, and 2.0 × 102 times dilution of their saturated vapor with air at room temperature, respectively. Also, presence of odorous substances (toiletries, fruits, dirty clothes, etc.), water, and amido-bond-containing organic compounds (typical organic amines, legal drugs, and different amino acids) shows little effect upon the sensing. More importantly, discrimination and identification of them can be realized by using the sensors in an array way. Based upon the discoveries, a conceptual, two-sensor based detector is developed, and non-contact detection of the drugs is realized.

High device efficiency and color-purity are the two essentials for high-quality organic light-emitting diodes (OLEDs). Multi-resonance (MR) molecules show great potentials for high color-purity OLEDs due to their sharp emission bands. However, most MR molecules exhibit emission limited from deep-blue to green spectral region. Herein, through peripherally decorating MR emitter with electron donors, a new approach enabling the emission spectra of MR emitters red-shift while retaining narrowband emission is demonstrated. By manipulating the numbers and electron-donating abilities of the peripheries, the first narrowband yellow emitter with emission maxima of 562 nm and a full-width at half-maximum (FWHM) of 30 nm is realized. Highly efficient OLEDs with an external quantum efficiency of over 24% and excellent color purity are fabricated by employing these newly developed MR molecules as emitters.

Constructing polycyclic aromatics-based highly emissive fluorophores with good solubility, tunable aggregated structures and properties is of great importance for film fabrication, solution processing and relevant functionality studies. Herein, we describe a general strategy to endow conventional organic fluorophores with enhanced solubility and modulated fluorescent properties via the incorporation into coordination-driven self-assembled metallacycles. A widely used fluorophore, pyrene, was decorated with two pyridyl groups to yield functionalized pyrene (4). Mixing 4 with three aromatic dicarboxylates with different lengths and a 90° Pt(II) metal acceptor in a 2:2:4 stoichiometric ratio resulted in the formation of three metallacycles (1, 2, and 3). The metallacycles display good solubility in polar organic solvents, highly aggregation-dependent fluorescence, and size-dependent emissions at higher concentrations. Moreover, metallacycle 2based, silica-gel supported film as fabricated is not only more emissive than the ligand, 4-based one, but also displays much improved sensing properties for amines in the vapor state as demonstrated by significantly increased response speed and decreased recovery time. The enhanced solubility, unique fluorescence behavior and multi-factor modulation character show that coordination-driven self-assembly can be utilized for the development of new fluorophores through simple modification of conventional fluorophores. The fluorophores synthesized this way possess not only complex topological structures but also good modularity and tunability in *

A conceptual sensor array for the efficient discrimination and fast detection of saturated alkanes and commonly found volatile solvents is reported.

Designing novel fluorophores with nonplanar structure and environmental sensitivity is of great significance for the development of high‐performance film‐based fluorescent sensors. Herein, a unique pentiptycene (P) and perylene bisimide (PBI)‐contained fluorescent dyad (P‐PBI‐P) displaying a switchable and tunable charge separated state is reported. It is demonstrated that this symmetrical and dumbbell‐like molecular dyad shows a greater extent of photoinduced intramolecular electron transfer than the asymmetrical dyad, P‐PBI. In addition, the charge separated state (P+‐PBI−‐P/P‐PBI−‐P+) of the fluorophore is super susceptive to solvent polarity, allowing sensitive detection of water content in organic liquids. Based on the finding, two P‐PBI‐P‐based fluorescent humidity sensors are fabricated, and they both show linear responses to air humidity within a range of at least 6.3% to 100% (relative humidity, RH). The response time is less than a few seconds, and the recovery time less than 1 min. Importantly, almost no hysteresis is found during a cyclic humidification and dehumidification test within the whole RH range studied. The superior performance of the humidity sensors based on the modulation of the charge separated state of a fluorophore constitutes an effective way for designing high‐performance film‐based fluorescent sensors.

BTEX (benzene, toluene, ethylbenzene, o-xylene, m-xylene, and p-xylene) represents a group of volatile organic compounds (VOCs) and constitutes a great threat to human health. However, sensitive, selective, and speedy detection of them on-site and in the vapor phase remains a challenge for years. Herein, we report a film-based fluorescent approach and a conceptual sensor, which shows unprecedented sensitivity, speed, and reversibility to the aromatic hydrocarbons in the vapor phase. In the studies, pentiptycene was employed to produce a nonplanar perylene bisimide (PBI) derivative, P-PBI. The compound was further utilized to fabricate the film. The novelty of the design is the combination of capillary condensation and solvent effect, which is expected to enrich the analytes from vapor phase and shows outputs at the same time. Importantly, the film permits instant response (∼3 s) and real-time identification (<1 min) of benzene and toluene from other aromatic hydrocarbons. The experimental detection limits (DLs) of the six analytes are lower than 9.2, 2.7, 1.9, 0.2, 0.4, and 0.4 ppm, which with the exception of benzene, are significantly lower than the NIOSH recommended long-term exposure limits. More importantly, the film is photochemically stable, and more than 300 repetitive tests showed no observable bleaching. In addition, the sensing is fully reversible. The superior performance of the film device is in support of the assumption that the combination of capillary condensation and solvation effect would constitute an effective way to design high-performance fluorescent films, especially for challenging chemical inert and photoelectronically inactive VOCs.

chiral TADF emitters for CP-OLEDs with high circularly polarized electroluminescence (CP-EL) and device performance. [4] Generally, there are two main strategies for achieving the above molecular design: i) a strategy based on the inherent chirality of TADF chromophores whose chiral elements are constructed by two achiral fluorophores hindering rotation in the 3D space; [4e,f,l] or ii) a strategy based on chiral perturbation in which the circularly polarized luminescence (CPL) activities of achiral TADF emitters are induced from chiral units directly decorated on the molecular structure. [2a,4a-d,g-k] Although the former strategy exhibits large dissymmetry factors, its main challenge is the separation of enantiomers when high-performance liquid chromatography or chiral column is used, which inevitably causes an increase in the preparation cost. In contrast, the synthetic procedure of the latter strategy usually begins with commercially available enantiomers; however, it often exhibits relatively small dissymmetry factors because of the long distance between the chiral units and luminescent cores. Notably, most circularly polarized TADF (CP-TADF) materials adopt the latter strategy but exhibit lower luminescence efficiency compared to the prototypical achiral emitters because of the structural relaxation of the nonluminous chiral unit and twisting donor-acceptor structures. Such structural features also inevitably cause a broad energy distribution in the excited state, leading to broad emission spectra and inferior color purity in CP-OLEDs.Despite considerable efforts to achieve innovative molecular designs, accessing CP-TADF materials with both excellent CPL and narrowband emission remains a formidable scientific challenge. Based on the novel design strategy for narrowband TADF materials proposed by Hatakeyama et al. in 2016, Wang et al. developed a series of narrowband green emitters by incorporating chiral (R/S)-octahydro-binaphthol into the periphery of multiple-resonance (MR)-induced TADF molecules. [5] Although all the emitters exhibited excellent device performances with a small full-width at half-maximum (FWHM) of ≈30 nm, the CP-EL signals were at the 10 −4 order of magnitude. Very recently, Chou et al. designed and synthesized asymmetrical peripherally locked MR-TADF enantiomers, which showed high device performance with a maximum external quantum efficiency (EQE) of up to 20.6% while maintaining a relatively high Organic light-emitting diodes (OLEDs) that can simultaneously achieve narrowband emission, high efficiency, and circularly polarized luminescence remain a formidable challenge. In this study, a simple strategy is developed to address this challenge. A chiral exciplex-forming co-host is first designed by employing a chiral donor and an achiral acceptor molecule. The chiral exciplex host enables an achiral green multiple-resonance thermally activated delayed fluorescence emitter to achieve high-performance circularly polarized electroluminescence (CP-EL) with a high external quantum efficiency...