Tremendous efforts have been devoted to develop efficient deep blue organic light-emitting diodes (OLEDs) materials with CIE y < 0.10 (Commission International de L’Eclairage (CIE)) and match the National Television System Committee (NTSC) standard blue CIE (x, y) coordinates of (0.14, 0.08) for display applications. However, deep blue fluorescent materials with an external quantum efficiency (EQE) over 5% are still rare. Herein, we report a phenanthroimidazole–sulfone hybrid donor–acceptor (D–A) molecule with efficient deep blue emission. D–A structure molecular design has been proven to be an effective strategy to obtain high electroluminescence (EL) efficiency. In general, charge transfer (CT) exciton formed between donor and acceptor is a weak coulomb bonded hole–electron pair and is favorable for the spin flip that can turn triplet excitons into singlet ones. However, the photoluminescence quantum yield (PLQY) of CT exciton is usually very low. On the other hand, a locally excited (LE) state normally possesses high PLQY owing to the almost overlapped orbital distributions. Hence, a highly mixed or hybrid local and charge transfer (HLCT) excited state would be ideal to simultaneously achieve both a large fraction of singlet formation and a high PLQY and eventually achieve high EL efficiency. On the basis of such concept, phenanthroimidazole is chosen as a weak donor and sulfone as a moderate acceptor to construct a D–A type molecule named as PMSO. The PMSO exhibits HLCT excited state properties. The doped device shows deep blue electroluminescence with an emission peak of 445 nm and CIE (0.152, 0.077). The maximum external quantum efficiency (EQE) is 6.8% with small efficiency roll-off. The device performance is among the best results of deep blue OLEDs reported so far.

Organic light‐emitting diodes (OLEDs) can promise flexible, light weight, energy conservation, and many other advantages for next‐generation display and lighting applications. However, achieving efficient blue electroluminescence still remains a challenge. Though both phosphorescent and thermally activated delayed fluorescence materials can realize high‐efficiency via effective triplet utilization, they need to be doped into appropriate host materials and often suffer from certain degree of efficiency roll‐off. Therefore, developing efficient blue‐emitting materials suitable for nondoped device with little efficiency roll‐off is of great significance in terms of practical applications. Herein, a phenanthroimidazole−anthracene blue‐emitting material is reported that can attain high efficiency at high luminescence in nondoped OLEDs. The maximum external quantum efficiency (EQE) of nondoped device is 9.44% which is acquired at the luminescence of 1000 cd m−2. The EQE is still as high as 8.09% even the luminescence reaches 10 000 cd m−2. The maximum luminescence is ≈57 000 cd m−2. The electroluminescence (EL) spectrum shows an emission peak of 470 nm and the Commission International de L'Eclairage (CIE) coordinates is (0.14, 0.19) at the voltage of 7 V. To the best of the knowledge, this is among the best results of nondoped blue EL devices.

A meta-linked donor–acceptor (D–A) structure was utilized to achieve high-efficiency and colour-purity near ultraviolet (NUV) in organic light-emitting diodes (OLEDs).

7521wileyonlinelibrary.com in realistic point of view owing to their low cost, non-involving of poor reproducibility of the optimum doping level, and concise control in device fabrication required for metal-complexed phosphorescent materials. [ 4 ] In principle, red fl uorescent emission comes from a narrow bandgap. To date, fl uorophores with narrow bandgap either have extended π conjugation or possess polar donor-acceptor (D-A) architectures. [ 5 ] The latter one has been proved to be a very promising way to effectively extend the emission to long wavelength. In addition, D-A system is also benefi cial to the recombination of carriers because the modifi cation of low highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels will effectively lower the injection barriers for electrons and holes in OLEDs. [ 6 ] More importantly, the electron fl ip can take place since the charge transfer (CT) excitons formed between the donor and acceptor is a weak Coulomb hole-electron pair, which would facilitate a large fraction of singlet excitons formation under electrical charge injection. [ 7 ] However, a major shortcoming of D-A compound is that the spatially separated HOMO-LUMO orbitals always result in the forbidden electronic transition, which usually leads to the low photoluminescence quantum effi ciency. [ 1d , 5 ] In contrast, the fl uorophores with local excited (LE) states are generally reported to acquire high photoluminescence quantum effi ciency; however, such fl uorophores generally exhibit low singlet exciton yields originated from the forbidden spin fl ip from triplet state to singlet state and their electroluminescent internal quantum effi ciencies are limited to ≈25%. [ 8 ] Recently, materials based on new principle, such as hybridized local and charge transfer (HLCT) with excitons that undergo a reverse intersystem crossing process (RISC) along the high-lying CT channel, has emerged to reach a compromise of LE and CT states to break through the 25% upper limit of η s . [ 9 ] Unlike many D-A compounds suffering from the low efficiency originated from CT effects, these materials benefi t from the large dipole moment of the CT state and a certain degree of orbital overlap of the LE state, which is a promising way to endow the material with a high photoluminescence quantum effi ciency as well as a large singlet exciton yield. Highly Effi cient Solid-State Near-Infrared Emitting Material Based on Triphenylamine and Diphenylfumaronitrile with an EQE of 2.58% in Nondoped Organic Light-Emitting DiodeXiao Han , Qing Bai , Liang Yao , Haichao Liu , Yu Gao , Jinyu Li , Liqun Liu , Yulong Liu , Xiaoxiao Li , Ping Lu , * and Bing Yang The development of effi cient near-infrared (NIR) emitting material is of current focus. Donor-acceptor (D-A) architecture has been proved to be an effective strategy to obtain narrow energy gap. Herein, a D-A-type NIR fl uorescent compound 2,3-bis(4′-(diphenylamino)-[1,1′-biphenyl]-4-yl) fumaronitrile (TPATCN) is synthesized and full...

Photoluminescence (PL) efficiency and exciton utilization efficiency are two key parameters to harvest high-efficiency electroluminescence (EL) in organic light-emitting diodes (OLEDs). But it is not easy to simultaneously combine these two characteristics (high PL efficiency and high exciton utilization) into a fluorescent material. In this work, an efficient combination was achieved through two concepts of hybridized local and charge-transfer (CT) state (HLCT) and "hot exciton", in which the former is responsible for high PL efficiency while the latter contributes to high exciton utilization. On the basis of a tiny chemical modification in TPA-BZP, a green-light donor-acceptor molecule, we designed and synthesized CzP-BZP with this efficeient combination of high PL efficiency of η(PL) = 75% in the solid state and maximal exciton utilization efficiency up to 48% (especially, the internal quantum efficiency of η(IQE) = 35% substantially exceed 25% of spin statistics limit) in OLED. The nondoped OLED of CzP-BZP exhibited an excellent performance: a green emission with a CIE coordinate of (0.34, 0.60), a maximum current efficiency of 23.99 cd A(-1), and a maximum external quantum efficiency (EQE, η(EQE)) of 6.95%. This combined HLCT state and "hot exciton" strategy should be a practical way to design next-generation, low-cost, high-efficiency fluorescent OLED materials.

Distributed fiber-optic vibration sensors receive extensive investigation and play a significant role in the sensor panorama. Optical parameters such as light intensity, phase, polarization state, or light frequency will change when external vibration is applied on the sensing fiber. In this paper, various technologies of distributed fiber-optic vibration sensing are reviewed, from interferometric sensing technology, such as Sagnac, Mach–Zehnder, and Michelson, to backscattering-based sensing technology, such as phase-sensitive optical time domain reflectometer, polarization-optical time domain reflectometer, optical frequency domain reflectometer, as well as some combinations of interferometric and backscattering-based techniques. Their operation principles are presented and recent research efforts are also included. Finally, the applications of distributed fiber-optic vibration sensors are summarized, which mainly include structural health monitoring and perimeter security, etc. Overall, distributed fiber-optic vibration sensors possess the advantages of large-scale monitoring, good concealment, excellent flexibility, and immunity to electromagnetic interference, and thus show considerable potential for a variety of practical applications.

Superhydrophobic membranes are desirable for separation of water-in-oil emulsions, membrane distillation, and membrane condensation. However, the lack of large-scale manufacture methods of superhydrophobic membranes hampers their widespread applications. Here, a facile method of coaxial electrospinning is provided to manufacture superhydrophobic membranes for the ultrafast separation of waterin-oil emulsions. Under the high-voltage electric field, the polydimethylsiloxane (PDMS)-coated polyvinylidene fluoride (PVDF) nanofibers and PDMS microspheres with PVDF nanobulges were integrated together during the electrospinning process. Moreover, asymmetric composite membranes with selective layers are designed to reduce the resistance of the mass transfer. Consequently, the as-prepared asymmetric composite membrane exhibits an ultrafast permeance and excellent separation efficiency of about 99.6%, outperforming most of the state-of-the-art membranes reported previously. Most importantly, the membrane could be as large as 770 cm 2 , could be manufactured continuously, and could be easily enlarged further via tailoring the roller receptor, showing strong promise in the separation of water-in-oil emulsions.

This paper presents a practical microassembly process for three-dimensional (3-D) microelectrode arrays for recording and stimulation in the central nervous system (CNS). Orthogonal lead transfers between the micromachined two-dimensional probes and a cortical surface platform are formed by attaching gold beams on the probes to pads on the platform using wire-free ultrasonic bonding. The low-profile (150 microns) outrigger design of the probes allows the bonding of fully assembled high-density arrays. Micromachined assembly tools allow the formation of a full 3-D probe array within 30 min. Arrays having up to 8 x 16 shanks on 200-micron centers have been realized and used to record cortical single units successfully. Active 3-D probe arrays containing on-chip CMOS signal processing circuitry have also been created using the microassembly approach. In addition, a dynamic insertion technique has been explored to allow the implantation of high-density probe arrays into feline cortex at high-speed and with minimal traumatic injury.