Kaiqi Ye

Luminescent chromism of boron diketonate crystals: distinct responses to different stresses.

However, the phenomenon that organic solids simultaneously exhibit ML responded to compressing (isotropic pressure), grinding (anisotropic pressure), and smashing (tensile force) has not yet been reported. In this work, we present a model which combines three ML into a luminescent organic molecule. The luminescent chromism of the crystalline sample responding to different mechanical stimuli has been experimentally elucidated in detail. These fi ndings refl ect the signifi cance of scientifi c defi nition and careful classifi cation on mechanoluminescence. The title boron-containing compound 1 is a novel molecule which can be easily synthesized in a high yield (Scheme S1, Supporting Information). The absorption and emission properties of 1 have been carefully investigated and shown in Figure S1 (Supporting Information). The HOMO and LUMO distributions are donated separately by phenylboron moiety and ligand part, respectively. Therefore, intramolecular change transfer is suggested from phenylboron to ligand which has been confi rmed by the strong solvent-polarity-dependent fl uorescent spectra. Solution diffusion of 1 from CH 2 Cl 2 to hexane produces block orange crystals ( 1OC ) with high quality and suitable size for X-ray diffraction analyses. Red crystals (1RC) with rod-like shape appear occasionally among orange ones and they rapidly turn into opaque when taken out from solution. The instability of 1RC is due to that CH 2 Cl 2 molecules are embodied in the crystalline lattice. Therefore, the red crystal is sealed in a capillary for X-ray data collection. The polymorphs 1OC and 1RC display orange and red emissions ( Figure 2 a−d), respectively, which are greatly redshifted compared with that of solution sample. The emission spectrum of crystals 1OC shows a main band peaked at 585 nm with a strong shoulder located around about 610 nm and that of 1RC displays only one broad band centered at 605 (Figure S3, Supporting Information), indicating that this organic material shows polymorph-dependent Mechanoluminescence (ML) is a luminescent chromism induced by mechanical stimuli such as smashing, grinding, and compressing, etc. [ 1,2 ] Luminescent organic materials with ML have attracted signifi cant attention in the past decades due to their potential applications in sensors and memory devices. ML of π-conjugated organic materials induced by anisotropic pressure are mostly investigated and largely documented in literatures due to the fact that a convenient operation, ground by a spoon or mortar, can effectively perturb the molecular arrangements and hence lead to ML. [ 3–20 ] In sharp contrast, there are only a few reports that describe ML actualized by isotropic compression because strict operating conditions are required for high-pressure measurement. [ 21–25 ] Organic crystals are very fragile and can be easily broken into pieces when they are scratched or picked. The freshly formed surfaces may display changed luminescence if the breach perturbs molecular arrangements of the cracks. However, this interesting ML has not yet attracted considerable attention probably due to the fact that molecules with such emission behaviors are very limited. [ 26 ]

Oxygen sensing materials based on mesoporous silica MCM-41 and Pt( ii )– porphyrin complexes

The preparation and properties of luminescent oxygen sensing materials based on two Pt(II)–porphyrin complexes: platinum meso-tetrakis(4-N-methylpyridyl)porphyrin (PtTMPyP4+) and platinum meso-tetrakis(4-N-pyridyl)porphyrin (PtTPyP) assembled in mesoporous silica (MCM-41) are described. The luminescence of Pt(II)–porphyrin/MCM-41 assembly materials can be extremely quenched by molecular oxygen with good sensitivity (I0/I100 > 7) and rapid response times ( 50). Even when the concentration of oxygen is 1%, the luminescence intensity of PtTMPyP4+/MCM-41 (20 mg g−1) can be quenched by 83.33%.

A novel tetraphenylsilane–phenanthroimidazole hybrid host material for highly efficient blue fluorescent, green and red phosphorescent OLEDs

A novel organosilane compound, bis(4-(1-phenylphenanthro[9,10-d]imidazol-2-yl)phenyl)diphenylsilane (Si(PPI)2), has been designed and synthesized. It has a high thermal decomposition temperature of 528 °C and is able to form an amorphous glass with a high glass-transition temperature of 178 °C. In addition, it possesses high singlet and triplet energies and displays efficient energy transfer to the selected blue fluorescent and green and red phosphorescent dopants when used as a host material. Electrochemical measurements and single-carrier devices indicate that Si(PPI)2 is a bipolar transport material, allowing the injection and transport of both electrons and holes. By using (Si(PPI)2) as a host, high-performance fluorescent blue (FB) and phosphorescent green (PG) and red (PR) OLEDs with a uniform and simple device configuration have been achieved. These OLEDs exhibit very high peak external quantum efficiency (EQE) and peak power efficiency (PE), i.e. 6.1% and 8.0 lm W−1 for FB, 19.2% and 51.1 lm W−1 for PG and 12.0% and 15.6 lm W−1 for PR. Moreover, the high-level EQE of 4.0, 19.1 and 10.6% and PE of 3.0, 41.6 and 7.5 lm W−1 can be maintained by FB, PG and PR, respectively, at the practical luminance of 100 cd m−2. Furthermore, the emission colors of these OLEDs remain almost unchanged within the whole range of driving voltages. Importantly, the blue OLED displays a pure blue emission (CIE: 0.18, 0.17).

Highly efficient phosphorescent OLEDs with host-independent and concentration-insensitive properties based on a bipolar iridium complex

A bipolar iridium complex, (ppy)2Ir(dipig), based on the ancillary ligand N,N′-diisopropyl-diisopropyl-guanidinate (dipig) with well-known cyclometalated (C^N) ligand ortho-(2-pyridyl)phenyl (ppy), is applicable in phosphorescent organic light-emitting diodes (PHOLEDs) as an efficient emitter, using easily available host materials and a simple device fabrication process. The corresponding PHOLEDs are dominated by an efficient direct-exciton-formation mechanism and show very high EL efficiency together with gratifying host- and doping-concentration-independent features. EL efficiency values of more than 93 lm W−1 for power efficiency (ηp) and 24% for external quantum efficiency (ηext) accompanied by little efficiency roll-off at high luminance are achieved in the (ppy)2Ir(dipig)-based devices by adopting the common materials 4,4′-bis(N-(1-naphthyl)-N-phenylamino)biphenyl (NPB) and 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI) as the host, with rather random concentration ranges of 8–15 wt% and 15–30 wt%, respectively. To the best of our knowledge, these values are the highest efficiencies ever reported for yellow PHOLEDs, and are even comparable with the highest levels for PHOLEDs in the scientific literature. Moreover, the ηp and ηext values of the non-doped device can reach 70 lm W−1 and 18% respectively. They are almost two times higher than those of the most efficient reported PHOLEDs based on a neat emitting layer (EML).

Deep‐Red to Near‐Infrared Thermally Activated Delayed Fluorescence in Organic Solid Films and Electroluminescent Devices

The design and synthesis of highly efficient deep red (DR) and near-infrared (NIR) organic emitting materials with characteristic of thermally activated delayed fluorescence (TADF) still remains a great challenge. A strategy was developed to construct TADF organic solid films with strong DR or NIR emission feature. The triphenylamine (TPA) and quinoxaline-6,7-dicarbonitrile (QCN) were employed as electron donor (D) and acceptor (A), respectively, to synthesize a TADF compound, TPA-QCN. The TPA-QCN molecule with orange-red emission in solution was employed as a dopant to prepare DR and NIR luminescent solid thin films. The high doped concentration and neat films exhibited efficient DR and NIR emissions, respectively. The highly efficient DR and NIR organic light-emitting devices (OLEDs) were fabricated by regulating TPA-QCN dopant concentration in the emitting layers.

A crystalline Cu–Sn–S framework for high-performance lithium storage

In order to address the increasing demands for clean energy, it is highly desirable to explore new electrode materials to improve the efficiency of lithium ion batteries (LIBs). In this work, we report the successful synthesis of a crystalline (H3O)2(enH2)Cu8Sn3S12 material via a surfactant-thermal strategy. The crystal structure analysis shows that the as-prepared chalcogenide has 3D interconnected channels occupied by disordered H2en2+ and H3O+. Taking advantage of porous structures and H2en2+ and H3O+ as stabilizers, (H3O)2(enH2)Cu8Sn3S12 has been explored as an anode material for lithium ion batteries. Our results exhibit a high capacity of 563 mA h g−1 at a current density of 0.1 A g−1 after 100 cycles. In addition, outstanding cycling properties are demonstrated with only 7.2% capacity loss from the 5th to 100th cycle. Our research could provide insight into the exploration of crystalline ternary thiostannate for lithium ion batteries in the future.

Morphology-dependent fluorescence ON/OFF of a beryllium complex: ACQ in amorphous solids, AEE in crystalline powders and the dark/bright fluorescence switch

Here we report a bis(2′-hydroxychalcone)beryllium complex Be(HC)2 that displays yellow fluorescence (λem = 557 nm; Φf = 0.10) in solution. Notably, the solution of this complex produces a non-emissive amorphous thin film (ACQ effect; fluorescent “OFF” state) but brightly emissive crystalline powders (AEE-active; fluorescent “ON” state) with deep red (λem = 678 nm; Φf = 0.27) or near infrared (λem = 700 nm; Φf = 0.20) emission colors and the fluorescent “ON” and “OFF” states can be smoothly transformed into each other by simple engineering processes: mechanical grinding and solvent fuming.

Red emissive diarylboron diketonate crystals: aggregation-induced color change and amplified spontaneous emission

Two novel diarylboron diketonates 1 and 2 were synthesized by the reaction of 1,3-diaryl-β-diketone with triphenylborane or fluorobis(pentafluorophenyl)borane. The synthesized boron-containing compounds exhibit intense greenish-blue or green emissions in solution but red fluorescence in crystals, showing an aggregation-induced colour change characteristic. Notably, the flake-like crystals of 1 and 2 show an evidently narrowed emission when irradiated by a pulsed laser beam and thus provide the first example of amplified spontaneous emission based on four-coordinate organoboron solids. This finding indicates the potential of four-coordinate boron species in organic solid lasing and thus may expand the application area of boron-containing materials.

CEE-active red/near-infrared fluorophores with triple-channel solid-state “ON/OFF” fluorescence switching

A class of beryllium complexes has been synthesized. These complexes display crystalline-enhanced emission (CEE) and exhibit morphology-dependent dark and bright red/NIR fluorescence. They show bright red/NIR emission in the crystalline form (λem: 635–700 nm; Φf: 0.27–0.40) and faint emission in the amorphous state. Their emission can be smoothly switched “ON” and “OFF” by simple grinding/solvent annealing processes. In addition, these complexes show interesting acid/base vapor induced fluorescence switching properties due to the amino groups of the ligands. Furthermore, the molecular packing modes of these complexes can be altered by heating and recovered by solvent annealing accompanied by fluorescence switching between dark and bright states. The first example of reversible triple-channel solid-state fluorescence “ON/OFF” switching realized through simple approaches of grinding/solvent annealing, acid/base vapor fuming, and heating/solvent annealing might have great significance on designing novel organic materials as chemical sensors.

Controllable Self‐Assembly of n‐Type Semiconductors to Microtubes and Highly Conductive Ultralong Microwires

www.MaterialsViews.com C O M M Controllable Self-Assembly of n-Type Semiconductors to Microtubes and Highly Conductive Ultralong Microwires U N IC By Xiaoyue Mu , Weifeng Song , Yu Zhang , Kaiqi Ye , Hongyu Zhang , * and Yue Wang * A IO N Increasing attention has been paid to one-dimensional (1D) organic semiconductor microstructures, for example microwires and microtubes. These highly ordered functional materials in their characteristic structures possess intriguing optical and electronic properties. [ 1 ] They are potential candidates as active components in a wide range of research fi elds including gas sensors, organic light-emitting diodes (OLEDs), organic fi eld effect transistors (OFETs), optical waveguide fi bers, photodetectors, and solar cells, etc. [ 2–7 ] The molecular packing in a highly organized 1D nanostructured semiconductor is a critical factor for its charge transport property. Recently, the self-assembly of π –conjugated molecules into 1D microor nanostructures has been widely studied, in which the molecules are well organized mainly through π – π stacking interactions. [ 8–10 ] The 1D alignment of π –conjugated molecules facilitates carrier transport hence improves the performance of optoelectronic devices. [ 11 ]