The combination of rigid acridine donor and 1,8-naphthalimide acceptor has afforded two orange-red emitters of NAI-DMAC and NAI-DPAC with high rigidity in molecular structure and strongly pretwisted charge transfer state. Endowed with high photoluminescence quantum yields (Φ ), distinct thermally activated delayed fluorescence (TADF) characteristics, and preferentially horizontal emitting dipole orientations, these emitters afford record-high orange-red TADF organic light-emitting diodes (OLEDs) with external quantum efficiencies of up to 21-29.2%, significantly surpassing all previously reported orange-to-red TADF OLEDs. Notably, the influence of microcavity effect is verified to support the record-high efficiency. This finding relaxes the usually stringent material requirements for effective TADF emitters by comprising smaller radiative transition rates and less than ideal Φ s.

Developing high‐efficiency solution‐processable thermally activated delayed‐fluorescence (TADF) emitters, especially in longer wavelength regions, is a formidable challenge. Three red TADF emitters, namely NAI_R1, NAI_R2, and NAI_R3, are developed by phenyl encapsulation and tert‐butyl substitution on a prototypical 1,8‐naphthalimide‐acridine hybrid. This design strategy not only grants these molecules high solubility, excellent thermal stability, and good film‐forming ability, but also pulls down their charge‐transfer (CT) energy levels excited states. Furthermore, dispersing these emitters into two different host materials of mCP and mCPCN finely tailors their CT‐state energy levels. More importantly, a synergistic combination of molecular engineering and host selection can effectively manipulate the competition between the radiative and nonradiative decay rates of the CT singlet states of these emitters and the reverse intersystem crossing from their triplet to singlet states. Consequently, the optimal combination of NAI_R3 emitter and mCP host successfully results in a state‐of‐the‐art external quantum efficiency (EQE) of 22.5% for solution‐processed red TADF organic light‐emitting diodes (OLEDs) with an emission peak above 620 nm. This finding demonstrates that a synergistic strategy of molecular engineering and host selection with TADF emitters could provide a new pathway for developing efficient solution‐processable TADF systems.

The immobilization of fluorescent photoinduced electron transfer (PET) switches/sensors into solid state, which usually cannot maintain their identical properties in solution, has remained a big challenge. Herein, a water-stable anthracene and maleimide appended zirconium-based-metal-organic framework (Zr-MOF; UiO-68-An/Ma) is reported. Unlike the regular intramolecular "fluorophore-spacer-receptor" format, the separated immobilization of fluorescent (anthracene) and acceptor (maleimide) groups into the framework of a multivariate MOF can also favor a pseudo-intramolecular fluorescent PET process, resulting in UiO-68-An/Ma with very weak fluorescence. Interestingly, after Diels-Alder reaction or thiol-ene reaction of maleimide groups, the pseudo-intramolecular fluorescent PET process in UiO-68-An/Ma fails and the solid-state fluorescence of the crystals is recovered. In addition, UiO-68-An/Ma shows an interesting application as solid-state fluorescent turn-on sensor for biothiols, with the naked eye response at a low concentration of 50 µmol L within 5 min. This study represents a general strategy to enable the efficient tuning of fluorescent PET switches/sensors in solid state, and considering the fluorescence of the PET-based MOFs can be restored after addition of analyte/target species, this research will definitely inspire to construct stimuli-responsive fluorescent MOFs for interesting applications (e.g., logic gate) in future.

The photophysical properties of four new quinoxaline derivatives featuring both AIE and TADF characteristics were controlled to give high EQEs.

Thermally activated delayed fluorescence (TADF) materials have provided new strategies for time‐resolved luminescence imaging (TRLI); however, the development of hydrophilic TADF luminophores for specific imaging in cells remains a substantial challenge. In this study, a mitochondria‐induced aggregation strategy for TRLI is proposed with the design and utilization of the hydrophilic TADF luminophore ((10‐(1,3‐dioxo‐2‐phenyl‐2,3‐dihydro‐1H‐benzo[de]isoquinolin‐6‐yl)‐9,9‐dimethyl‐9,10‐dihydroacridin‐2‐yl)methyl)triphenylphosphonium bromide (NID‐TPP) . Using a nonconjugated linker to introduce a triphenylphosphonium (TPP + ) group into the 6‐(9,9‐dimethylacridin‐10(9 H )‐yl)‐2‐phenyl‐1H‐benzo[ de ]isoquinoline‐1,3(2 H )‐dione (NID) TADF luminophore preserves the TADF emission of NID‐TPP . NID‐TPP shows clear aggregation‐induced delayed fluorescence enhancement behavior, which provides a practical strategy for long‐lived delayed fluorescence emission in an oxygen‐containing environment. Finally, the designed mitochondrion‐targeting TPP + group in NID‐TPP induces the adequate accumulation of NID‐TPP and results in the first reported TADF‐based time‐resolved luminescence imaging and two‐photon imaging of mitochondria in living cells.

The exact energies of the lowest singlet and triplet excited states in organic chromophores are crucial to their performance in optoelectronic devices. The possibility of utilizing singlet fission to enhance...

Developing a durable and efficient photocatalyst for H2 evolution is highly desirable to expedite current research on solar–chemical energy conversion. In this work, we rationally designed and synthesized a direct Z-scheme system based on three-dimensional hierarchical CdS decorated with Co9S8 nanoparticles toward photocatalytic H2 evolution. The composition, microstructure, and optical properties of the hybrids were thoroughly investigated. Photocatalytic performances revealed that the optimized CdS/Co9S8-15 composite exhibited the highest H2-evolution rate of 5.15 mmol h–1 g–1, which is approximately 6.8 and 257.5 times that of CdS and Co9S8, respectively. In addition, this novel composite catalyst also displayed long-term stability without apparent debasement in photocatalytic activity. On the basis of the analysis of UV–vis diffuse reflectance spectroscopy, photocurrent response, electrochemical impedance spectra, and photoluminescence, the reinforced H2 evolution performance of the CdS/Co9S8 samples was attributed to a synergistic effect including boosted light absorption capacity, increased separation and transfer efficiency of photogenerated electron/hole pairs, as well as much stronger reducibility of electrons in the conduction band of Co9S8. Finally, the photocatalytic mechanism for this composite was proposed and discussed in detail.

This work incorporates the nuclear ensemble approach into emission simulation of thermally activated delayed fluorescence (TADF) emitters with strong charge transfer (CT). The vibrational distribution of the excited state is described by an ensemble of nuclear geometries with vertical transition properties computed for each point in the ensemble through the time-dependent density functional theory (TDDFT) method. Compared to TDDFT calculation at stationary geometry, this method provides a better estimate of oscillator strength and distribution of transition dipole moments (TDMs). Four different types of CT states are explored. For the twisted intramolecular CT state, the oscillator strength is promoted strongly and direction distribution of TDMs is concentrated, while it increases less with dispersed TDMs for the through-space CT state. The present work provides a feasible calculation method for TADF emitters and will compensate the flaws of the traditional stationary point TDDFT method which hamper their application in understanding and predicting the photophysical properties of emitters with strong CT characteristics.