Stimulating Phonon Bottleneck Effect in Organic Semiconductors by Charge-Transfer-Mediated J-Aggregation.

Hot carriers rapidly lose kinetic energies on a subpicosecond time scale, posing significant limitations on semiconductors' photon-conversion efficiencies. To slow the hot carrier cooling, the phonon bottleneck effect is constructed prevalently in quantum-confined structures with discrete energy levels. However, the maximum energy separation (ΔEES) between the energy levels is in a range of several hundred meV, leading to unsatisfactory cooling time. To address this, we design a novel organic semiconductor capable of forming intermolecular charge transfer (CT) in J-aggregates, where the lowest singlet excited state (S1) splits into two states due to the significant interplay between the Coulomb interaction and intermolecular CT coupling. The ΔEES between the two states can be adjusted up to 1.02 eV, and an extremely slow carrier cooling process of ∼72.3 ps was observed by femtosecond transient absorption spectroscopy. Moreover, the phonon bottleneck effect was identified in organic materials for the first time, and CT-mediated J-aggregation with short-range interactions was found to be the key to achieving large ΔEES. The significantly prolonged carrier cooling time, compared to <100 fs in the isolated molecule (10-6 M), highlights the potential of organic molecules with diversified aggregation structures in achieving long-lived hot carriers. These findings provide valuable insights into the intrinsic photophysics of electron-phonon scattering in organic semiconductors.

Resonance-Induced Dynamic Triplet Exciton Population for Photoactivated Organic Ultralong Room Temperature Phosphorescence.

Dynamically populating triplet excitons under external stimuli is desired to develop smart optoelectronic materials, but it remains a formidable challenge. Herein, we report a resonance-induced excited state regulation strategy to dynamically modulate the triplet exciton population by introducing a self-adaptive N-C═O structure to phosphors. The developed phosphors activated under high-power ultraviolet irradiation exhibited enhanced photoactivated organic ultralong room temperature phosphorescence (PA-OURTP) with lifetimes of up to ∼500 ms. The enhanced PA-OURTP was ascribed to activated N-C═O resonance variation-induced intersystem crossing to generate excess triplet excitons. The excellent PA-OURTP performance and ultralong deactivation time under ambient conditions of the developed materials could function as a reusable recorded medium for time-sensitive information encryption through optical printing. This study provides an effective approach to dynamically regulating triplet excitons and offers valuable guidance to develop high-performance PA-OURTP materials for security printing applications.

Spontaneous Compositional-Interfacial Co-Modification Engineering via Ion Exchange Reaction Between Perovskite and Electron-Transporting Layer for Exceptionally Long-Term Stability of Photovoltaics.

The long-term stability of perovskite solar cells (PSCs) is still challenging for commercialization and mainly linked to the life span of perovskite films. Herein, a spontaneous compositional-interfacial co-modification strategy is developed based on the ion exchange reaction by introducing ammonium hexafluorophosphate (NH4PF6) into antisolvent to form gradient structures through a simple one-step solvent engineering. With the assistance of the ion exchange reaction, NH4PF6 forms a multifunctional structure to protect perovskite films from both internal and external factors for the exceptionally long-term stability of photovoltaics. The reason for this is linked to the high hydrophobicity of NH4PF6 for preventing H2O invasion, suppressing ion migration by forming hydrogen bonding, and reducing perovskite defects. The resulting unencapsulated devices show exceptionally long-term stability under standardized the International Summit on Organic Photovoltaic Stability (ISOS) protocols, with over 94%, 81%, and 83% retained power conversion efficiencies after aging tests under N2 (ISOS-D-1I), ambient air (ISOS-D-1), and 85 °C (ISOS-D-2I) for 14016, 2500, and 1248 h, respectively. These performances compare well with the state-of-the-art stability of inverted PSCs. Further investigations are conducted to study the evolution of macroscopic morphology and microscopic crystal structure in aged perovskite films, aiming to provide evidence supporting the aforementioned improvements in stability.

Mn(II)-Based Metal Halide with Near-Unity Quantum Yield for White LEDs and High-Resolution X-ray Imaging.

Metal halides have drawn great interest as luminescent materials and scintillators due to their outstanding optical properties. Exploring new types of phosphors with easy production processes, excellent photophysical properties, high light yields, and environmentally friendly compositions is crucial and quite challenging. Herein, a novel Mn(II)-based metal halide (4-BTP)2MnBr4 was produced using a facile solvent evaporation method, which exhibited a strong green emission peaking at 524 nm from the d-d transition of tetrahedral-coordinated Mn2+ ion and a near-unity quantum yield. The prepared white light-emitting diode device has a wide color gamut of 100.7% NTSC with CIE chromaticity coordinates of (0.32, 0.32). In addition, (4-BTP)2MnBr4 demonstrates excellent characteristics in X-ray scintillation, including a high light yield of 98 000 photons/MeV, a sensitive detection limit of 37.4 nGy/s, excellent resistance to radiation damage, and successful demonstration of X-ray imaging with high resolution at 21.3 lp/mm, revealing the potential for application in diagnostic X-ray medical imaging and industry radiation detection.

Direct Population of Triplet States for Efficient Organic Afterglow through the Intra/Intermolecular Heavy-Atom Effect.

Organic afterglow is a fascinating phenomenon with exceptional applications. However, it encounters challenges such as low intensity and efficiency, and typically requires UV-light excitation and facile intersystem crossing (ISC) due to its spin-forbidden nature. Here, we develop a novel strategy that bypasses the conventional ISC pathway by promoting singlet-triplet transition through the synergistic effects of the intra/intermolecular heavy-atom effect in aromatic crystals, enabling the direct population of triplet excited states from the ground state. The resulting materials exhibit a bright organic afterglow with a remarkably enhanced quantum efficiency of up to 5.81%, and a significantly increased organic afterglow lifetime of up to 157 microseconds under visible light. Moreover, given the high-efficiency visible-light excitable organic afterglow emission, the potential application is demonstrated in lifetime-resolved, color-encoded, and excitation wavelength-dependent pattern encryption. This work demonstrates the importance of the direct population method in enhancing the organic afterglow performance and red-shifting the excitation wavelength, and provides crucial insights for advancing organic optoelectronic technologies that involve triplet states.

Achieving Stimuli-Responsive Amorphous Organic Afterglow in Single-Component Copolymer through Self-Doping.

The development of stimuli-responsive materials with afterglow emission is highly desirable but remains a formidable challenge in a single-component material system. Herein, we propose a strategy to achieve photoactivated afterglow emission in a variety of amorphous copolymers through self-doping, endowed by the synergetic effect of self-host-induced guest sensitization and thermal-processed polymer rigidification for boosting the generation and stabilization of triplet excitons. Upon continuous ultraviolet illumination for regulating the oxygen concentration, a photoactivated afterglow showing increased lifetimes from 0.34 to 867.4 ms is realized. These afterglow emissions can be naturally or quickly deactivated to the pristine state under ambient conditions or heating treatment. Interestingly, programmable and reusable afterglow patterns, conceptual pulse-width indicators, and "excitation-time lock" Morse code are successfully established using stimuli-responsive afterglow polymers as recorded media. These findings offer an avenue to construct a single-component polymeric system with photoactivated organic afterglow features and demonstrate the superiority of stimuli-responsive materials for remarkable applications.

Time-Dependent Colorful Circularly Polarized Organic Ultralong Room Temperature Phosphorescence from a Single-Component Chiral Molecule.

Colorful circularly polarized organic ultralong room temperature phosphorescence (CP-OURTP) materials have attracted much attention due to their superior optoelectronic properties for various applications. However, the development of colorful CP-OURTP materials in a single-component molecular system is currently facing great challenges. Herein, a feasible strategy is proposed to develop colorful CP-OURTP material from a single-component chiral molecule by introducing a chiral unit into the phosphorescence chromophore. A dual CP-OURTP band originated from inherent triplet excitons emission showing a lifetime of 946.44 ms and triplet-triplet annihilation induced delayed emission with a short lifetime of 209.91 ms as well as maximum asymmetry factors of ≈10-3 are realized. Owing to the changed OURTP intensity ratios between inherent CP-OURTP and delayed emission at different delayed times, time-dependent colorful CP-OURTP turned from yellow to green is obtained. This study provides a potential platform to prepare circularly polarized material systems showing colorful luminescent properties.

Multifunctional Resonance Bridge-Mediated Dynamic Modulation of Perovskite Films For Enhanced Intrinsic Stability of Photovoltaics.

The improving intrinsic stability, determining the life span of devices, is a challenging task in the industrialization of inverted perovskite solar cells. The most important prerequisite for boosting intrinsic stability is high-quality perovskite films deposition. Here, a molecule, N-(2-pyridyl)pivalamide (NPP) is utilized, as a multifunctional resonance bridge between poly(triarylamine) (PTAA) and perovskite film to regulate the perovskite film quality and promote hole extraction for enhancing the device intrinsic stability. The pyridine groups in NPP couple with the phenyl groups in PTAA through π-π stacking to improve hole extraction capacities and minimize interfacial charge recombination, and the resonance linkages (NCO) in NPP dynamically modulate the perovskite buried defects through strong PbO bonds based on the fast self-adaptive tautomerization between resonance forms (NCO and N+ CO- ). Because of the combined effect of the reduction defect density and improved energy level in the perovskite buried interfaces as well as the optimized crystal orientation in perovskite film enabled by the NPP substrate, the devices based on NPP-grown perovskite films show an efficiency approaching 20% with negligible hysteresis. More impressively, the unencapsulated device displays start-of-the-art intrinsic photostability, operating under continuous 1-sun illumination for 2373 h at 65 °C without loss of PCE.

Ultralong Red Room-Temperature Phosphorescence of 2D Organic-Inorganic Metal Halide Perovskites for Afterglow Red LEDs and X-ray Scintillation Applications.

Organic-inorganic metal hybrid perovskites (OIHPs) have emerged as a promising class of materials for next-generation optoelectronic applications. However, the realization of red and near-infrared (NIR) room-temperature phosphorescence (RTP) in these materials remains limited. In this study, a very strong red RTP emission centered at 610 nm is achieved by doping Mn2+ ions into Cd-based 2D OIHPs. Notably, the optimized B-EACC:Mn2+ exhibited a high quantum yield of 44.11%, an ultralong lifetime of up to 378 ms, and excellent stability against high temperatures and various solvents, surpassing most reported counterparts of 2D OIHPs. Moreover, the B-EACC:Mn2+ can be used as a red emitter for coating an ultraviolet light-emitting diode chip, exhibiting an observable afterglow to the naked eye for approximately 4 s. In addition, the B-EACC:Mn2+ demonstrates interesting characteristics under X-ray excitation, exhibiting X-ray response at radiation doses in the range of 34.75-278 µGy s-1. This work suggests the infinite possibility of doping guest ions to realize red RTP in 2D OIHPs, promoting the development of long-persistent phosphorescent emitters for multifunctional light-emitting applications.

Achieving narrowband emissions with tunable colors for multiple resonance-thermally activated delayed fluorescence materials: effect of boron/nitrogen number and position.

The boron/nitrogen (B/N)-based multiple resonance-thermally activated delayed fluorescence (MR-TADF) materials with tunable colors have attracted widespread attention owing to their great potential in next-generation display, white lighting, and imaging applications. Numerous MR-TADF emitters with different B/N number and position have been reported to realize full-color narrowband emissions. To gain a better understanding of the effect of B/N number and position on the photo-electronic properties, geometric and electronic properties, Huang-Rhys factors and reorganization energies, charger transfer and absorption/emission properties were analyzed in detail to determine the structure-property relationship for the investigated molecules. The calculated results show that the molecules with para-atoms having the same electronic characteristics (para-B-π-B/para-N-π-N) exhibited smaller structural relaxations upon excitation, and the molecules with increased B/N atoms showed more obvious short-range charge transfer (SRCT) properties. Besides, the para-B-π-N and para-B-π-B/para-N-π-N substructures could reduce and enhance the donor and acceptor strengths, respectively, leading to tunable HOMO-LUMO gaps and emission colors. Such theoretical insights well rationalize the experimental results, revealing that the small reorganization energy and dominant SRCT property should be two key factors in realizing narrowband emissions of MR-TADF materials. These findings and understandings could give an in-depth insight into the structure-property relationship, providing molecular design strategies for the exploration of narrowband MR-TADF materials with tunable emission colors.

Resonance-Induced Stimuli-Responsive Capacity Modulation of Organic Ultralong Room Temperature Phosphorescence.

Organic ultralong room temperature phosphorescence (OURTP) materials having stimuli-responsive attributes have attracted great attention due to their great potential in a wide variety of advanced applications. It is of fundamental importance but challengeable to develop stimuli-responsive OURTP materials, especially such materials with modulated optoelectronic properties in a controlled manner probably due to the lack of an authentic construction approach. Here, we propose an effective strategy for OURTP materials with controllably regulated stimuli-responsive properties by engineering the resonance linkage between flexible chain and phosphor units. A quantitative parameter to demonstrate the stimuli-responsive capacity is also established by the responsivity rate constant. The designed OURTP materials demonstrate efficient photoactivated OURTP with lifetimes up to 724 ms and tunable responsivity rate constants ranging from 0.132 to 0.308 min-1 upon continuous UV irradiation. Moreover, the applications of stimuli-responsive resonance OURTP materials have been illustrated by the rewritable paper for snapshot and Morse code for multiple information encryption. Our works, which enable the accomplishment of OURTP materials capable of on-demand manipulated optical properties, demonstrate a viable design to explore smart OURTP materials, giving deep insights into the dynamically stimuli-responsive process.

Recent Advances on Host-Guest Material Systems toward Organic Room Temperature Phosphorescence.

The design and characterization of purely organic room-temperature phosphorescent (RTP) materials for optoelectronic applications is currently the focus of research in the field of organic electronics. Particularly, with the merits of preparation controllability and modulation flexibility, host-guest material systems are encouraging candidates that can prepare high-performance RTP materials. By regulating the interaction between host and guest molecules, it can effectively control the quantum efficiency, luminescent lifetime, and color of host-guest RTP materials, and even produce RTP emission with stimuli-responsive features, holding tremendous potential in diverse applications such as encryption and anti-counterfeiting, organic light-emitting diodes, sensing, optical recording, etc. Here a roundup of rapid achievement in construction strategies, molecule systems, and diversity of applications of host-guest material systems is outlined. Intrinsic correlations between the molecular properties and a survey of recent significant advances in the development of host-guest RTP materials divided into three systems including rigid matrix, exciplex, and sensitization are presented. Providing an insightful understanding of host-guest RTP materials and offering a promising platform for high throughput screening of RTP systems with inherent advantages of simple material preparation, low-cost, versatile resource, and controllably modulated properties for a wide range of applications is intended.

Constructing high-performance TADF polymers from non-TADF monomers: a computational investigation.

Thermally activated delayed fluorescence (TADF) polymers excelling in simple, low-cost and large-area solution process ability have attracted tremendous attention recently, but it remains a great challenge for the design of such materials due to the lack of reliable molecular construction guidelines. Here we perform a systematic computational investigation on the construction of TADF polymers from non-TADF monomers to elucidate the effects of polymerization sites, substituent positions and substituent types. The results indicate that the polymerization of 3,6-carbazole-based monomers with different substituents is efficient to build TADF polymers due to their facile π-conjugation extendability. Especially, polymers with para-phenyl-substituted monomers are promising in light of their separated frontier molecular orbitals for small ΔEST with favorable energy levels, bipolar charge transport properties and relatively strong absorption/emission intensity, which should be highly attractive for experimental investigations. These findings and insights are important in revealing the structure-property relation of TADF polymers made from non-TADF monomers with important clues for understanding the construction mechanism and molecular design principles of TADF polymers.

Corilagin attenuates osteoclastic osteolysis by enhancing HO-1 and inhibiting ROS.

Chinese herbal medicine has well-established therapeutic effects in various diseases. Corilagin (Cor), a gallic acid tannin in Phyllanthus niruri L., has anti-inflammatory and antioxidant effects in many diseases. However, its role in osteoclast-related bone diseases has not been determined. In vitro, bone marrow macrophages (BMMs) were extracted and isolated to differentiate into osteoclasts. The effects of Cor on osteoclast formation, bone resorption, and reactive oxygen species (ROS) production were performed. In addition, quantitative real-time polymerase chain reaction and western blot analysis were used to evaluate the effect of Cor on oxidative stress-related pathways, which are nuclear factors-κB ligand-receptor activator (RANKL) stimulates important downstream pathways. Furthermore, microcomputed tomography and bone histomorphometry were performed to analyze the therapeutic effect of Cor in mouse models of lipopolysaccharide (LPS)-mediated bone defects in vivo. Cor influenced the nuclear factor of activated T cells 1 (NFATc1) signaling pathway and reduced ROS in RANKL-treated osteoclasts, thereby inhibiting osteoclast formation and bone resorption. Moreover, Cor protected against LPS-mediated skull defects in vivo. In sum, our results confirm that Cor can inhibit osteoclastogenesis and intracellular oxidative stress. In addition, the inflammatory bone defect induced by LPS was also attenuated by Cor. Accordingly, Cor is a new candidate therapeutic agent for osteoclast-mediated osteolytic diseases.

Aircraft Landing Gear Retraction/Extension System Fault Diagnosis with 1-D Dilated Convolutional Neural Network.

The faults of the landing gear retraction/extension(R/E) system can result in the deterioration of an aircraft's maneuvering conditions; how to identify the faults of the landing gear R/E system has become a key issue for ensuring aircraft take-off and landing safety. In this paper, we aim to solve this problem by proposing the 1-D dilated convolutional neural network (1-DDCNN). Aiming at developing the limited feature information extraction and inaccurate diagnosis of the traditional 1-DCNN with a single feature, the 1-DDCNN selects multiple feature parameters to realize feature integration. The performance of the 1-DDCNN in feature extraction is explored. Importantly, using padding dilated convolution to multiply the receptive field of the convolution kernel, the 1-DDCNN can completely retain the feature information in the original signal. Experimental results demonstrated that the proposed method has high accuracy and robustness, which provides a novel idea for feature extraction and fault diagnosis of the landing gear R/E system.

An Organic Laser Based on Thermally Activated Delayed Fluorescence with Aggregation-Induced Emission and Local Excited State Characteristics.

The spatial separation between the highest occupied and the lowest unoccupied molecular orbitals (HOMO and LUMO) in thermally activated delayed fluorescent (TADF) molecules leads to charge transfer (CT) states, which degrade the oscillator strength of emission transition and sacrifices high solid-state photoluminescence quantum yield (PLQY), together limiting its application in organic solid-state lasers (OSSLs). Here, we demonstrated organic microwire lasers from TADF emitters that combine aggregation induced emission (AIE) and local excited (LE) state characteristics. The unique AIE and LE feature lead to a PLQY approaching 50 % and a high optical gain of 870 cm-1 for TADF microwires. The regenerated singlet excitons by reverse intersystem crossing (RISC) process are conducive to population inversion. As a result, we demonstrated microwire lasers around 465 nm with a low threshold of 3.74 µJ cm-2 . Therefore, our work provides insight to design TADF materials for OSSLs.

Facile Preparation of MoS2 Nanocomposites for Efficient Potassium-Ion Batteries by Grinding-Promoted Intercalation Exfoliation.

Efficient exfoliations of bulk molybdenum disulfide (MoS2 ) into few-layered nanosheets in pure phase are highly attractive because of the promising applications of the resulted 2D materials in diversified optoelectronic devices. Here, a new exfoliation method is presented to prepare semiconductive 2D hexagonal phase (2H phase) MoS2 -cellulose nanocrystal (CNC) nanocomposites using grinding-promoted intercalation exfoliation (GPIE). This method with facile grinding of the bulk MoS2 and CNC powder followed by conventional liquid-phase exfoliation in water can not only efficiently exfoliate 2H-MoS2 nanosheets, but also produce the 2H-MoS2 /CNC 2D nanocomposites simultaneously. Interestingly, the intercalated CNC sandwiched in MoS2 nanosheets increases the interlayer spacing of 2H-MoS2 , providing perfect conditions to accommodate the large-sized ions. Therefore, these nanocomposites are good anode materials of potassium-ion batteries (KIBs), showing a high reversible capacity of 203 mAh g-1 at 200 mA g-1 after 300 cycles, a good reversible capacity of 114 mAh g-1 at 500 mA g-1 , and a low decay of 0.02% per cycle over 1500 cycles. With these impressive KIB performances, this efficient GPIE method will open up a new avenue to prepare pure-phase MoS2 and promising 2D nanocomposites for high-performance device applications.

Simultaneously Enhancing Efficiency and Stability of Perovskite Solar Cells Through Crystal Cross-Linking Using Fluorophenylboronic Acid.

Organic-inorganic metal halide perovskites are regarded as one of the most promising candidates in the photovoltaic field, but simultaneous realization of high efficiency and long-term stability is still challenging. Here, a one-step solution-processing strategy is demonstrated for preparing efficient and stable inverted methylammonium lead iodide (MAPbI3 ) perovskite solar cells (PSCs) by incorporating a series of organic molecule dopants of fluorophenylboronic acids (F-PBAs) into perovskite films. Studies have shown that the F-PBA dopant acts as a cross-linker between neighboring perovskite grains through hydrogen bonds and coordination bonds between F-PBA and perovskite structures, yielding high-quality perovskite crystalline films with both improved crystallinity and reduced defect densities. Benefiting from the repaired grain boundaries of MAPbI3 with the organic cross-linker, the inverted PSCs exhibit a remarkably enhanced performance from 16.4% to approximately 20%. Meanwhile, the F-PBA doped devices exhibit enhanced moisture/thermal/light stability, and specially retain 80% of their initial power conversion efficiencies after more than two weeks under AM 1.5G one-sun illumination. This work highlights the impressive advantages of the perovskite crystal cross-linking strategy using organic molecules with strong intermolecular interactions, providing an efficient route to prepare high-performance and stable planar PSCs.

Phosphine Sulfide-Based Bipolar Host Materials for Blue Phosphorescent Organic Light-Emitting Diodes.

Three phosphine sulfide-based bipolar host materials, vizCzPhPS, DCzPhPS, and TCzPhPS, were facilely prepared through a one-pot synthesis in excellent yields. The developed hosts exhibit superior thermal stabilities with the decomposition temperatures (Td) all exceeding 350 °C and the melting temperatures (Tm) over 200 °C. In addition, their triplet energy (ET) levels are estimated to be higher than 3.0 eV, illustrating that they are applicable to serve as hosts for blue phosphorescent organic light-emitting diodes (PhOLEDs). The maxima luminance, current efficiency (CE), power efficiency (PE), and external quantum efficiency (EQE) of 17,223 cd m-2, 36.7 cd A-1, 37.5 lm W-1, and 17.5% are achieved for the blue PhOLEDs hosted by CzPhPS. The PhOLEDs based on DCzPhPS and TCzPhPS show inferior device performance than that of CzPhPS, which might be ascribed to the deteriorated charge transporting balance as the increased number of the constructed carbazole units in DCzPhPS and TCzPhPS molecules would enhance the hole-transporting ability of the devices to a large extent. Our study demonstrates that the bipolar hosts derived from phosphine sulfide have enormous potential applications in blue PhOLEDs, and the quantity of donors should be well controlled to exploit highly efficient phosphine sulfide-based hosts.

Modulating Tri-Mode Emission for Single-Component White Organic Afterglow.

Achieving single-component white organic afterglow remains a great challenge owing to the difficulties in simultaneously supporting long-lived emissions from varied excited states of a molecule for complementary afterglow. Here, an extraordinary tri-mode emission from the radiative decays of singlet (S1 ), triplet (T1 ), and stabilized triplet (T1 * ) excited states was proposed to afford white afterglow through modulating the singlet-triplet splitting energy (ΔEST ) and exciton trapping depth (ETD ). Low-lying T1 * for yellow afterglow was constructed by H-aggregation engineering with large ETD and trace isomer doping, while high-lying T1 and S1 for blue afterglow with thermally activated emission feature were realized by reducing ΔEST through donor-acceptor molecular design. Therefore, the single-component white afterglow with high efficiency of 14.1 % and a lifetime of 0.61 s was achieved by rationally regulating the afterglow intensity ratios of complementary emissions from S1 , T1 , and T1 *.