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A deep-blue exciplex with thermally activated delayed fluorescence (TADF) at 444 nm enabled organic light-emitting diodes (OLEDs) with CIE coordinates of (0.152, 0.075) and EQE up to 4.83%, meanwhile, which can also serve as a co-host for wide color phosphorescent OLEDs.

A facile scenario is proposed to design DBA-type molecules with E(T2) > E(S1) ≥ 2E(T1), promising to realize 200% exciton utilization through a three-step mechanism for organic electroluminescence.

Singlet fission (SF), the conversion of one high-energy singlet to two low-energy triplets, provides the potential to increase the efficiency of photovoltaic devices. In the SF chromophores with C2h symmetry, exemplified by polyenes, singlet-to-triplet conversion generally involves a low-lying 21Ag dark state, which serves as either a multiexciton (ME) intermediate to promote the SF process or a parasitic trap state to shunt excited-state populations via internal conversion. This controversial behavior calls for a deep understanding of dark-state-related photophysics involving the higher-lying singlet state. However, the optical "dark" and "transient" nature of these dark states and strong correlation feature of double exciton species make their characterization and interpretation challenging from both experimental and computational perspectives. In the present work combining transient spectroscopy and multireference electronic structure calculations (XDW-CASPT2), we addressed a new photophysical model, i.e., a high-lying 31Ag dark-state-mediated ultrafast SF process in the benzodipyrrolidone (BDPP) skeleton. Such a 31Ag dark state with distinctive double excitation character, described as the ME state, could be populated from the initial 11Bu bright state on an ultrafast time scale given the quasi-degeneracy and intersection of the two electronic states. Furthermore, the suitable optical band gap and triplet energy, high triplet yield, and excellent photostability render BDPP a promising SF candidate for photovoltaic devices. These results not only enrich the arsenal of SF materials but also shed new insights into the understanding of dark-state-related photophysics, which could promote the development of new SF-active materials.

Two-dimensional (2D) cocrystals open a new way to get 2D functional materials via crystal engineering instead of molecular engineering. Here, large-area 2D cocrystals with length reaching several millimeters with strong near-infrared (NIR) absorption have been successfully designed and prepared. Driven by the intermolecular charge-transfer (CT) interactions, zinc tetraphenylporphyrin (donor) and C 60 (acceptor) self-assemble into a NIR cocrystals with absorption wavelength up to 1080 nm. By tailoring the growth solvents and processes, the cocrystal morphologies can be tuned from 1D nanowires, 2D nanosheets to large-area 2D cocrystal films with length reaching several millimeters. Impressively, due to the highly ordered donor-acceptor arrangement, the CT absorption in the 2D cocrystals is significantly enhanced and becomes comparable to singlet absorption. The uniform 2D cocrystals, with enhanced CT absorption in the NIR region, displays a high responsivity of 2424 mA/W to NIR light and a fast response time of 0.6 s. The excellent device performance can be attributed to the generation of long-lived free charge carriers as revealed by transient absorption spectroscopy and the optimization of device configuration. This work shows an example of controlled growth of 2D cocrystals for broadband photodetectors, which reveals the brilliant future of cocrystal films for high-performance electronics and paves their way towards large-scale, integrated, flexible, practical applications.

A small energy gap between charge transfer (CT) singlet and triplet states enables thermally activated delayed fluorescence (TADF). Nevertheless, the small oscillator strength associated with CT states and their long exciton lifetimes are detrimental to establishing a population inversion for stimulated emission (SE), hindering the application of a TADF material in organic lasers. Here, we demonstrated that a TADF molecule of sulfide-substituted difluoroboron derivatives can achieve stimulated emission in microcrystals by employing a new molecular design, in which an ultrafast reverse intersystem crossing (RISC) process was achieved between a hybrid locally excited CT (HLECT) singlet S1 and a high-lying triplet T2 (3HLECT) state. Femtosecond transient abaorption and time-reolved PL spectra reveal that the two states of S1 and T2 equilibrate within a time of 180 ps. In addition, the energetic spacing of ΔES1–T2 = 0.11 eV enables delayed fluorescence involving the T2 state at room temperature. Besides, the extremely fast exciton lifetime (0.31 μs) that decreases the probability of carrier annihilation, the HLECT singlet provides larger oscillator strength and therefore larger SE cross-section than those of the CT state. A multimode TADF laser was realized based on the good optical feedback (cavity quality factor Q ≈ 2000) provided by Fabry Perot (FP) microcrystal microcavity. Our results not only confirm that the high-lying Tn state plays a key role in the RISC process of TADF, but also provides a design of TADF gain materials.

Synthetic routes for heteroatom-containing polycyclic aromatic hydrocarbons (H-PAHs) with alkyl and aryl substitution are demonstrated. Three H-PAHs, including heteroatom-containing rubicenes (H-rubicenes), angular-benzothiophenes (ABTs), and indenothiophene (IDTs) were successfully synthesized by two key steps, including polysubstituted olefin formation and cyclization. Specifically, ABT and H-rubicenes were comprehensively investigated by single-crystal X-ray diffraction, NMR spectroscopy, UV-vis absorption, cyclic voltammetry, transient absorption, and single-crystal OFET measurements.

Sub-picosecond hole transfer has been recently observed in several narrow band gap nonfullerene small-molecule acceptor (NFA)-based binary blended organic solar cell (OSC) systems operating with ne...

Quaternary blended organic solar cells utilize four blended material components (one donor plus three acceptors, two donors and two acceptors, or three donors plus one acceptor) as the active layer materials. The use of four material components allows us to have more material selections and more mechanism choices to improve the photon-to-electron conversion efficiency. In this contribution, we present a new case of quaternary material system, that shows 17.1% efficiency obtained by adding IDIC and PC71BM as the guest acceptors of the host binary of PM6:Y6. The lowest unoccupied molecular orbital (LUMO) levels of IDIC and PC71BM are both higher than that of Y6, which is one reason to obtain increased open-circuit voltage ( V oc) in the quaternary device. Upon introduction of IDIC and PC71BM as the acceptor guests, the hole and electron mobilities are both increased, which contributes to the increased short-circuit current-density ( J sc). Effects of the weight ratios of the three acceptor components are investigated, which demonstrates that the increased hole and electron mobilities, the accelerated hole-transfer, and the reduced monomolecular recombination are the factors contributing to the increased J sc and fill-factor. This case of quaternary device demonstrates the applicability of the quaternary strategy in increasing the device functions and hence the efficiencies in the field of organic photovoltaic cells.

Singlet fission (SF) holds the potential to boost the maximum power conversion efficiency of photovoltaic devices. Internal conversion (IC) has been considered as one of the major competitive deactivation pathways to transform excitation energy into heat. Now, using time-resolved spectroscopy and theoretical calculation, it is demonstrated that, instead of a conventional IC pathway, an unexpected intramolecular singlet fission (iSF) process is responsible for excited state deactivation in isoindigo derivatives. The 1 TT state could form at ultrafast rate and nearly quantitatively in solution. In solid films, the slipped stacked intermolecular packing of a thiophene-functionalized derivative leads to efficient triplet pair separation, giving rise to an overall triplet yield of 181 %. This work not only enriches the pool of iSF-capable materials, but also contributes to a better understanding of the iSF mechanism, which could be relevant for designing new SF sensitizers.

Organic solid-state lasers (OSSLs) have been paid great attention due to their ease-of-fabrication, low cost and tailor-made molecular tunability. Optical gain materials of OSSLs are currently focused on fluorescent materials, which can bring only 25% exciton utilization for future current-injection OSSLs due to spin statics under electrical excitation. While thermally active delayed fluorescent (TADF) materials can obtain a theoretical 100% internal quantum efficiency by harvesting triplet excitons. However, OSSLs based on TADF materials remain largely unexplored yet. Here, we report the first TADF-based OSSL from whispering-gallery mode microring resonator arrays fabricated by a confined solution-growth method. The newly designed TADF emitter of carbozyl borondifluoride curcuminoid derivative, namely, CAZ-A, when doped into a host matrix of 4,4′-bis(N-carbazolyl)-1,10-biphenyl (CBP), reaches the highest gain-coefficient of 640 cm–1 at 4 wt %. These MRs with well-controlled sizes and uniform geometries c...

Salt stress is one of the major abiotic stress which severely limits plant growth and reduces crop productivity across the world. In the present study, the effects of exogenous pyridoxal-5-phosphate (vitamin B6, VB6) on seedling growth and development of wheat under salt stress were investigated. The results showed that exogenous application of pyridoxal-5-phosphate (VB6) significantly increased the RWC, biomass, the concentration of photosynthetic pigments, proline, the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), together with decreasing the content of Malondiadehyde (MDA) and hydrogen peroxide (H2O2) in wheat leaves under salt stress. Meanwhile, the transcript level of P5CR, P5CS, SOD, TaSOS1 and TaSOS4 were also up-regulated after treatment with pyridoxal-5-phosphate. VB6 acts as a signal in regulating the activities of plant antioxidant enzymes and SOS pathway to improve resistance to salt stress. The current study results may give an insight into the regulatory roles of VB6 in improving salt stress and VB6 could be an easily and effective method to improve salt-stress tolerance to wheat in the field condition. It is urgency to understand the molecular mechanism of VB6 to enhance the salt tolerance of wheat in the next work.

Photoelectrochemical (PEC) water splitting via semiconductors is an effective and feasible method for synthesizing renewable hydrogen (H2) fuels. In this study, β-In2S3 nanosheets were first grown on conductive glass. Then, we prepared P-doped β-In2S3 nanosheets with an amorphous InPOx overlayer via the incomplete phosphorization of pristine β-In2S3 nanosheets. When we used this material as photoanode in a PEC cell for water splitting, the photocurrent density drastically increased to 2.2 mA cm−2 at 1.23 V versus a reversible hydrogen electrode (vs. RHE). It enhanced 15 times as the pristine β-In2S3 nanosheets, which was only 0.15 mA cm−2 at 1.23 V vs. RHE (solar standard spectrum, 100 mW cm−2). The photoelectric conversion efficiency as high as 0.65% at a low potential of 0.81 V vs. RHE was achieved for the phosphorized β-In2S3 nanosheets. A series of experiments proved that the P-doping accelerated semiconductor charge-transport and the InPOx overlayer played cocatalyst role. We penetratingly investigated the pathway of charge transfer via femtosecond transient absorption. The results showed one pathway of charge transfer in pristine β-In2S3 photoanode. However, there were two pathways (core/shell coupling and shallow trap states) for charge transfer in the phosphorized β-In2S3 photoanode, which improved the performance of its PEC water oxidation.

In intramolecular SF (iSF), the strong coupling nature and confinement of diffusional separation of 1(TT) limits the extraction and harnessing of triplet energy. In order to investigate the possible 1(TT) separation and the role of molecular parameters on it, a series of iSF-capable dibenzopentalene derivatives (DBPs) have been synthesized and their photoinduced dynamics are monitored. iSF takes place in DBPs, accompanied by consecutive 1(TT) separation in polycrystalline film with almost 100% yield. It is suggested the strong intermolecular coupling provided by the closely packing configuration in the film facilitates the disentanglement of correlated 1(TT). Highly efficient triplet pair separation to yield free triplets makes one step forward for utilizing triplet energy from iSF materials for further optoelectronic applications.

We have proposed a facile strategy to achieve large triple gap by manipulating the aromaticity and the transition properties of the low-lying excited states, then theoretically designed and experimentally verified a series of donor-bridge-acceptor based on partially conjugated five-membered rings with high aromaticity in T1 state to meet the harsh energy conditions required for hot exciton materials and for singlet fission materials.

Stimulated emission depletion (STED) nanoscopy plays a key role in achieving sub-50 nm high spatial resolution for subcellular live-cell imaging. To avoid re-excitation, the STED wavelength has to be tuned at the red tail of the emission spectrum of fluorescent probes, leading to high depletion laser power that might damage the cell viability and functionality. Herein, with the highly emissive silica-coated core-shell organic nanoparticles (CSONPs) enabling a giant Stokes shift of 150 nm, ultralow power STED is achieved by shifting the STED wavelength to the emission maximum at 660 nm. The stimulated emission cross section is increased by ∼20-fold compared to that at the emission red tail. The measured saturation intensity and lateral resolution of our CSONP are 0.0085 MW cm-2 and 25 nm, respectively. More importantly, long-term (>3 min) dynamic super-resolution imaging of the lysosomal fusion-fission processes in living cells is performed with a resolution of 37 nm.

The exploitation of singlet fission (SF) in photovoltaic devices is restricted by the limited number of SF materials available and the conflicting requirement of intermolecular interactions to satisfy both efficient SF and subsequent triplet extraction. Intramolecular SF (iSF) represents an emerging alternative and may prove simpler to implement in devices. On account of the excellent chemical structure tunability and solution processability, conjugated polymers have emerged as promising candidates for iSF materials despite being largely underexplored. It remains a significant challenge to develop SF-capable conjugated polymers and achieve efficient dissociation of the formed triplet pairs simultaneously. In this contribution, we present a new iSF material in a

Organic room-temperature phosphorescence (ORTP) has been demonstrated successfully in solids. In contrast, solution-phase ORTP is rarely achieved, because the T1 → S0 phosphorescence is too slow to compete against nonradiative decay and the oxygen-quenching effect. Here, we reported that suppression of Kasha's rule is a strategy to achieve solution-phase ORTP from the high-lying T2 state by spatially separating T2 and T1 on different parts of the molecule (CzCbDBT) composed of carbonyl (Cb), dibenzothiophene (DBT), and carbazole moiety (Cz). On one hand, intersystem crossing (ISC) is much faster from S1 to T2 than that to T1, owing to the small energy-gap ΔES1-T2 and large spin-orbital coupling ξS1-T2. On the other hand, T2 → T1 internal conversion is inhibited owing to spatial separation, i.e., T2 on CbDBT and T1 on Cz, respectively. Also, combination of very fast radiative decay from T2 to S0 owing to large ξT2-S0, the efficient solution-phase ORTP emission from the T2 state was finally achieved.

Singlet fission (SF) materials hold the potential to increase the power conversion efficiency of solar cells by reducing the thermalization of high-energy excited states. The major hurdle in realizing this potential is the limited scope of SF-active materials with high fission efficiency, suitable energy levels, and sufficient chemical stability. Herein, using theoretical calculation and time-resolved spectroscopy, we developed a highly stable SF material based on dipyrrolonaphthyridinedione (DPND), a pyrrole-fused cross-conjugated skeleton with a distinctive adaptive aromaticity (dual aromaticity) character. The embedded pyrrole ring with 4

Metal-halide perovskites have long carrier diffusion lengths, low trap densities and high carrier mobilities, and are therefore of value in the development of photovoltaics and light-emitting diodes. However, the presence of thermally activated carriers in the materials leads to high noise levels, which limits their photodetection capabilities. Here, we show that ultrasensitive photodetectors can be created from single-crystalline nanowire arrays of layered metal-halide perovskites. A series of nanowires was fabricated in which layer-by-layer self-organization of insulating organic cations and conductive inorganic frameworks, along the nanowire length, creates high resistance in the interior of the crystals and high conductivity at the edges of the crystals. Using these structures, high-performance photodetection was achieved with responsivities exceeding 1.5 × 104 A W−1 and detectivities exceeding 7 × 1015 jones. Our state-of-the-art device performance originates from a combination of efficient free-carrier edge conduction and resistive hopping barriers in the layered perovskites. Photodetectors made from single-crystalline nanowire arrays of layered metal-halide perovskites exhibit detectivities of more than 7 × 1015 jones, due to a nanowire structure that combines high resistance in the interior of the crystals and high conductivity at the edges of the crystals.

Miniaturized nanowire nanolasers of 3D perovskites feature a high gain coefficient; however, room-temperature optical gain and nanowire lasers from 2D layered perovskites have not been reported to date. A biomimetic approach is presented to construct an artificial ligh-harvesting system in mixed multiple quantum wells (QWs) of 2D-RPPs of (BA)2 (FA)n-1 Pbn Br3n+1 , achieving room-temperature ASE and nanowire (NW) lasing. Owing to the improvement of flexible and deformable characteristics provided by organic BA cation layers, high-density large-area NW laser arrays were fabricated with high photostability. Well-controlled dimensions and uniform geometries enabled 2D-RPPs NWs functioning as high-quality Fabry-Perot (FP) lasers with almost identical optical modes, high quality (Q) factor (ca. 1800), and similarly low lasing thresholds.

A series of multi-branched compounds D1 – D3 combining a triphenylamine core with one, two or three benzylidene cyclopentylidene malononitrile branches, respectively, were synthesized. The linear photophysical property, photochemical stability, thermal stability, and nonlinear absorption under 1064 nm pulsed lasers with pulse durations in both nanosecond and femtosecond regimes of D1–D3 were investigated. The results showed that the main optical limiting mechanism of D1 – D3 under femtosecond pulses was two-photon absorption (2PA), but their excited state absorption (ESA) became the main contributor for their optical limiting behaviors under nanosecond pulses. Meanwhile, introducing a multi-branched structure has much stronger impact on the ESA spectrum of D3 than on its linear absorption spectrum compared with the monomer D1 . The largest ESA cross-section of D3 was the main contributor to its enhancement of effective 2PA in nanosecond regime. Combining with its best thermal and photochemical stability, the three-branched compound D3 was proved as a good optical limiting material for 1064 nm nanosecond pulsed lasers.

The development of metal-free organic room temperature phosphorescence (RTP) materials has attracted increasing attention because of their applications in sensors, biolabeling (imaging) agents and anticounterfeiting technology, but remains extremely challenging owing to the restricted spin-flip intersystem crossing (ISC) followed by low-yield phosphorescence that cannot compete with nonradiative relaxation processes. Here, we report a facile strategy to realize highly efficient RTP by doping iodo difluoroboron dibenzoylmethane (I-BF2dbm-R) derivatives into a rigid crystalline 4-iodobenzonitrile (Iph-C≡N) matrix. We found that halogen bonding between cyano group of Iph-C≡N matrix and iodine atom of I-BF2dbm-R dopant is formed in doped crystals, i.e., Iph-C≡N···I-BF2dbm-R, which not only suppresses nonradiative relaxation of triplets but also promotes the spin–orbit coupling (SOC). As a result, the doped crystals show intense RTP with an efficiency up to 62.3%. By varying the substituent group R in I-BF2dbm...

A new class of donor–acceptor heterodimers based on two singlet fission (SF)-active chromophores, i.e., pentacene (Pc) and perylenediimide (PDI), was developed to investigate the role of charge transfer (CT) state on the excitonic dynamics. The CT state is efficiently generated upon photoexcitation. However, the resulting CT state decays to different energy states depending on the energy levels of the CT state. It undergoes extremely rapid deactivation to the ground state in polar CH2Cl2, whereas it undergoes transformation to a Pc triplet in nonpolar toluene. The efficient triplet generation in toluene is not due to SF but CT-mediated intersystem crossing. In light of the energy landscape, it is suggested that the deep energy level of the CT state relative to that of the triplet pair state makes the CT state actually serve as a trap state that cannot undergoes an intramolecular singlet fission process. These results provide guidance for the design of SF materials and highlight the requisite for more wide...

A holographic display using tunable multi-stage gratings for angular multiplexing is proposed. Using a liquid crystal waveguide and cascaded gratings, it could continuously steer light in a large r...

Singlet fission (SF), in which one singlet exciton (S₁) splits into two triplets (T₁) on adjacent molecules through a correlated triplet-pair ¹(TT) state, requires precise but difficult tuning of exciton energetics and intermolecular electronic couplings in the solid state. Here we demonstrate anti-aromatic 4nπ dibenzopentalenes (DPs) as a new class of single-chromophore based intramolecular SF materials, which exhibit optically allowed S2 state with E(S₂) > 2E(T₁) and optically forbidden S₁ state. Ultrafast population transfer from high-lying S₂ state to ¹(TT) state was observed in monomeric solution of styryl-substituted DP (SDP) on sub-picosecond timescale. More importantly, we provide compelling evidence of exciton diffusion (ED) of ¹(TT) state to yield two individual long-lived triplets in SDP thin film. The overall triplet yield via iSF and subsequent triplet-pair diffusion can be as high as 142±10% in thin-film.

Singlet fission (SF), a spin-allowed multiexciton generation process, experienced renewed interest in the last decade due to its potential to increase the efficiency of photovoltaic devices. The hurdles now lie in the limited range of SF-capable materials and demanding morphology requirement for an efficient fission process. Although primary fission to yield triplet pair (1TT) can occur independently of film morphology in intramolecular singlet fission (iSF) materials, the separation of the 1TT state has been shown to be highly dependent on the packing motif and morphologies. In this work, we have demonstrated that both iSF and triplet pair separation processes took place irrelevant of molecular order and/or film morphology in a series of pentalene compounds. With the >180% fission efficiency, the suitable triplet energy levels, and the long lifetime of the triplet excitons, these iSF systems can be integrated into practical photovoltaic application.

Exosomes are endosome-derived extracellular vesicles that are released upon the fusion of multivesicular bodies with the plasma membrane. These vesicles contain proteins, lipids, and nucleic acids and are found in various human body fluids. Exosomes can transfer bioactive molecules to nearby or distant recipient cells, thereby affecting their function. Recently, exosomes have gained importance as a medium of communication between tumor cells. An increasing number of studies have found that non-coding RNAs in tumor cell-derived exosomes can regulate tumor microenvironments, inhibit immune cell function, promote the growth and invasion of tumor cells, and impart resistance to chemicals in tumor cells. In this review, we focus on the effects of exosomal long non-coding RNAs (lncRNAs) on tumors. As exosomes and their parent cells have similar biological characteristics and coated lncRNAs can exist stably in vivo without being degraded by RNases, exosomal lncRNAs have emerged as novel non-invasive tumor biomarkers for use in the early diagnosis and evaluation of prognosis of tumors. Advancements in the field have led to the development of a variety of techniques in exosomal non-coding RNA research. Currently, most methods include the separation and purification of exosomes, followed by RNA extraction, reverse transcription, and subsequent analyses; thus, these processes are very tedious and vulnerable to contamination and could lead to inaccurate and inconsistent results. Thus, there has been an increase in the development of detection methods for exosomal RNAs. Here, we discuss the existing research methods, their advantages and disadvantages, and a few new techniques.

The excited-state intramolecular proton transfer (ESIPT) process provides a real four-level system, which forms the working basis of many laser dyes in solutions but remains largely unexplored in the solid-state gain medium. Herein, we modulated the keto* and enol* emissions by switching the intramolecular hydrogen-bond to the intermolecular hydrogen-bond in the solid-state for tuning the emission colors of ESIPT-microcrystal lasers. Both model compounds of 2′-hydroxychalcone derivatives of M1 and M2 exhibit very similar dual enol* and keto* emissions in the aprotic solvents, typical for ESIPT-active molecules. When aggregated into hexagonal-plate microcrystals (HPMCs), the intramolecular hydrogen-bond ensures the photoinduced proton tautomerization from enol* to keto* tautomers, resulting in intense red fluorescence of M1 HPMCs at 647 nm from the keto* form. In sharp contrast, the introduction of an extra hydroxyl group into M2 leads to the formation of an intermolecular hydrogen bond between two adjacent molecules, which suppresses the ESIPT process in the solid-state and therefore leads to intense green emission of M2 HPMCs at 537 nm from the enol* form. The solid-state photoluminescence efficiencies of HPMCs of M1 and M2 are as high as 42% and 51%, respectively. Moreover, well-faceted HPMCs of both M1 and M2 can function as whispering-gallery mode microresonators, enabling microlasers with very low laser thresholds of 10.8 μJ cm−2 for red-emissive M1-HPMCs and 9.4 μJ cm−2 for green emissive M2-HPMCs.

Although graphene has unique electronic and optical properties, its application in photodetectors is still limited due to its low optical absorption. In this work, graphene was first functionalized with diketopyrrolopyrrole derivatives (TDPP, TTDPP) to enhance the light absorption of hybrid systems. The morphology, optical absorption and photoluminescence properties were investigated in order to elucidate the interaction between the graphene and diketopyrrolopyrrole derivatives. The time-resolved fluorescence data verified the occurrence of the interface charge transfer between TDPP or TTDPP molecules and graphene in the hybrids. Visible-light photodetectors based on TTDPP/RGO hybrids exhibit a maximum photoresponsivity of 34.2 A W−1 and the on/off ratio is 282. We conclude that the high photoresponse is consistent with the efficient charge-transfer process occurring at the interface between TTDPP and graphene. 2D-graphene here serves not only as a superior supporting matrix for anchoring the sensitizer molecules but also as an excellent electron mediator to adjust electron transfer. Our research paves the way to build high-performance optoelectronic devices based on 2D graphene and organic compounds.

Zero-dimensional (0D) perovskite Cs4PbBr6 has been speculated to be an efficient solid-state emitter, exhibiting strong luminescense on achieving quantum confinement. Although several groups have reported strong green luminescence from Cs4PbBr6 powders and nanocrystals, doubts that the origin of luminescence comes from Cs4PbBr6 itself or CsPbBr3 impurities have been a point of controversy in recent investigations. Herein, we developed a facile one-step solution self-assembly method to synthesize pure zero-dimensional rhombohedral Cs4PbBr6 micro-disks (MDs) with a high PLQY of 52% ± 5% and photoluminescence full-width at half maximum (FWHM) of 16.8 nm. The obtained rhombohedral MDs were high quality single-crystalline as demonstrated by XRD and SAED patterns. We demonstrated that Cs4PbBr6 MDs and CsPbBr3 MDs were phase-separated from each other and the strong green emission comes from Cs4PbBr6. Power and temperature dependence spectra evidenced that the observed strong green luminescence of pure Cs4PbBr6 MDs originated from direct exciton recombination in the isolated octahedra with a large binding energy of 303.9 meV. Significantly, isolated PbBr64− octahedra separated by a Cs+ ion insert in the crystal lattice is beneficial to maintaining the structural stability, depicting superior thermal and anion exchange stability. Our study provides an efficient approach to obtain high quality single-crystalline Cs4PbBr6 MDs with highly efficient luminescence and stability for further optoelectronic applications.

We report the synthesis of penicillamine-protected Ag20 nanoclusters (NCs), with properties of high monodispersity, red fluorescence and water solubility. Full characterization of the Ag20 NCs is addressed, along with first-principles optimization calculations, revealing the chemical composition and structure of the as-prepared Ag NCs within a molecular formula [Ag20(DPA)18-H]−. Moreover, natural bond orbital (NBO) analysis demonstrates the charge-transfer interactions between the ligand and Ag atoms, and helps in understanding the origins of fluorescence of Ag20 NCs related to the ligand-to-metal charge transfer (LMCT) mechanism. Further, fluorescence chemosensing of the Ag20 NCs is demonstrated for tracing copper ions with high sensitivity and selectivity in aqueous solution.

A triazole-conjugated pyrene derivative (DTP) with strong two-photon absorption has been synthesized via CuAAC reaction. It can readily self-assemble into ultra-long 1D single-crystal nanowires by a one-step anti-solvent diffusion method, which exhibit exceptional two photon optical waveguides with low optical loss during light propagation. Single-particle spectroscopy of the nanowires clarifies that one short wavelength emission band results from the DTP monomer and the other longer wavelength band is responsible for the aggregate state of DTP. Moreover, DTP monomer and aggregate state emission peaks intensity of a single nanowire have opposite trends by changing the polarization of the incident light, owning to the two orthogonal optical transition dipoles. Besides, the excitation wavelength was changing from 760 nm to 850 nm, resulting in a red-shift of the maximum emission peak from 466 to 522 nm and the variation of the CIE coordinates from blue to green. This result may open up new perspectives in optoelectronic devices.

Photoinduced interfacial electron transfer plays a key role in photoactive organic/inorganic hybrid nanomaterials and remains elusive with regard to interfacial energy level alignment. In this study, n-type organic semiconductor 1,6,7,12-tetrachloro-3,4,9,10-Perylenetetracarboxylicdiimide (PDI) molecules bearing carboxylic acid groups at nitrogen positions were grafted onto the surface of the Zinc oxide (ZnO) nanoparticles, and then blended with p-type poly (3-hexylthiophene) P3HT. The addition of PDI facilitates the charge transfer process from P3HT to ZnO, which was characterized by steady-state spectroscopy and time-resolved fluorescence spectroscopy. High performance visible-light detector based on P3HT/PDI/ZnO has been fabricated. This provides guidelines for the construction of optoelectronic devices.

Solid state emissive materials with high quantum yields and tunable emissions are desirable for various applications. A new TPE derivative (1) with two carbazole moieties and two cyano groups is reported, which shows typical aggregation induced emission behavior. Four crystals 1a, 1b, 1c, and 1d are obtained after crystallization from N,N-dimethylformamid (DMF), trichloromethane (CHCl3 ), tetrahydrofuran (THF), and dichloromethane (CH2 Cl2 ), respectively. Crystal structural analyses reveal that (i) molecules of 1 co-crystallize with DMF, CHCl3 , THF, and CH2 Cl2 in 1a, 1b, 1c, and 1d, respectively, and (ii) conformations of 1 are different within 1a, 1b, 1c, and 1d, and compound 1 within crystal 1a adopts the most twisting conformation. Crystalline solids 1a, 1b, 1c, and 1d exhibit high emission quantum yields up to 0.65, but their emission colors are varied from blue to green. In comparison, the amorphous solid of 1 is yellow-emissive with emission maximum at 542 nm. Moreover, the blue- or green-emissive crystalline solids and the yellow-emissive amorphous solid can be inter-converted by the grinding of crystalline solids and exposure of the amorphous solid to vapors of appropriate solvents. It is also demonstrated that microrods of 1a, 1b, and 1d show typical optical waveguiding behavior.

Obtaining a large open-circuit voltage (VOC ) and high short-circuit current density (JSC ) simultaneously is important in improving power conversion efficiency (PCE) of organic photovoltaics. The ternary strategy with using a higher lowest unoccupied molecular orbital (LUMO) level nonfullerene acceptor (NFA) guest can achieve increased VOC , yet JSC is decreased or maintained, so it's still a challenge to offer increased VOC and JSC values concurrently via the newly presented VOC -increased ternary strategy. To overcome this issue, a new narrow bandgap NFA TT-S-4F is reported by introducing 3,6-dimethoxylthieno[3,2-b]thiophene (TT) as π-spacers to connect electron-rich core with terminal groups, so as to upshift the LUMO level and extend π-system. When adding 10% TT-S-4F into binary system based on PTB7-Th:IEICO-4F, the higher-LUMO-level of TT-S-4F, the increased charge mobilities, the reduced trap-assisted combination loss, and a finer nanofiber structure and increased phase separation size are obtained, which simultaneously promotes JSC , VOC , and fill factor (FF), thus obtaining an optimal PCE (12.5% vs 11.5%). This work illustrates that an extending conjugated backbone with large π-spacers and inclusion of alkylthiophenyl side-chains is a concept to synthesize NFA guests for use on the VOC -increased ternary strategy that enables to realize simultaneously increased JSC , VOC , and FF.

The Central Solenoid (CS) model coil, which is responsible for developing and verifying the larger-scale superconducting magnet technology of China Fusion Engineering Test Reactor (CFETR), has been designed and is currently being manufactured at ASIPP. The energy storage of the CS model coil is 407MJ, so a reliable quench protection system is needed to ensure the safety of the coil when a quench occurs. This paper describes the progress of the quench protection system. The two-stage commutating current technique is used to solve the difficulties that the breaker cannot directly break the high DC current. For the key components in the circuit, the prototype of the breaker was manufactured and the performance test was carried out. The engineering design and manufacture of the discharge resistor were carried out. An experimental study of the quench protection circuit was carried out to verify the feasibility of the design. Besides, the reliability of the quench protection control system is qualitatively analyzed based on the fault tree.

Photoinitiated interfacial electron transfer from organic semiconductors to inorganic ones is extremely important in organic/inorganic hybrid optoelectronic materials. Herein, we have prepared hybrid ZnO nanorods by grafting TDPP and TTDPP molecules through carboxyl acid groups. The steady-state spectroscopy results revealed that photoluminescence was subjected to severe quenching in the hybrid nanocomposites. Furthermore, time-resolved fluorescence and femtosecond transient absorption data verified the occurrence of the interface charge transfer between TDPP or TTDPP molecules and ZnO nanorods in the hybrid nanocomposites. The high performance UV-vis photodetector based on the TTDPP/ZnO hybrid have been fabricated with a photoresponsivity of 16.9 A W−1 and an on/off ratio as high as 104. The excellent visible-light photoresponse of the hybrid device can be attributed to the broadband absorption after the anchoring of the TTDPP compound on the surface of ZnO nanorods, the efficient cascade charge transfer process and the excellent capability of ZnO nanorods to provide direct and stable pathways for the transport of photogenerated electrons toward the collection electrode. This provides guidelines for the construction of organic/inorganic hybrids for optoelectronic applications.

Organic solid-state lasers (OSSLs) have been a topic of intensive investigations. Perylenediimide (PDI) derivatives are widely used in organic thin-film transistors and solar cells. However, OSSLs based on neat PDIs have not been achieved yet, owing to the formation of H-aggregates and excimer trap-states. Here, we demonstrated the first PDI-based OSSL from whispering-gallery mode (WGM) hexagonal microdisk (hMD) microcavity of N,N'-bis(1-ethylpropyl)-2,5,8,11-tetrakis(p-methyl-phenyl)-perylenediimide (mp-PDI) self-assembled from solution. Single-crystal data reveal that mp-PDI molecules stack into a loosely packed twisted brickstone arrangement, resulting in J-type aggregates that exhibit a solid-state photoluminescence (PL) efficiency φ15%. Moreover, we found that exciton-vibration coupling in J-aggregates leads to an exceptional ultrafast radiative decay, which reduces the exciton diffusion length, in turn, suppresses bimolecular exciton annihilation (bmEA) process. These spectral features, plus the optical feedback provided by WGM-hMD microcavity, enable the observation of multimode lasing as evidenced by nonlinear output, spectral narrowing, and temporal coherence of laser emission. With consideration of high carrier-mobility associated with PDIs, hMDs of mp-PDI are attractive candidates on the way to achieve electrically driven OSSL.

Hybrid fluorescent nanoparticles (NPs) capable of fluorescing near-infrared (NIR) light (centered ∼730 nm) upon excitation of 800 nm laser light were constructed. A new type of conjugated polymer with two-photon excited fluorescence (TPEF) feature, P-F8-DPSB, was used as the NIR-light harvesting component and the energy donor while a NIR fluorescent dye, DPA-PR-PDI, was used as the energy acceptor and the NIR-light emitting component for the construction of the fluorescent NPs. The hybrid NPs possess δ value up to 2.3 × 10(6) GM per particle upon excitation of 800 nm pulse laser. The excellent two-photon absorption (TPA) property of the conjugated polymer component, together with its high fluorescence quantum yield (ϕ) up to 45% and the efficient energy transfer from the conjugated polymer to NIR-emitting fluorophore with efficiency up to 90%, imparted the hybrid NPs with TPEF-based NIR-input-NIR-output fluorescence imaging ability with penetration depth up to 1200 μm. The practicability of the hybrid NPs for fluorescence imaging in Hela cells was validated.