Recently, the light-emitting diode (LED) has been considered as an energy-saving and environment-friendly lighting technology，which is ten times more energy efficient than conventional incandescent lights. As an emerging photoelectric material,...

Perovskite light-emitting diodes (PeLEDs) have attracted considerable attention due to their low cost, high efficiency and narrowband emission. However, poor operational lifetime limits their practical application and the degradation mechanism is not yet clear. Herein, the effect of typical phenylalkylamine and alkylamine ligands on optoelectrical properties and operational stability of cesium/methylammonium lead bromide PeLEDs were systematically investigated. The phenylethylamine (PEA) modified PeLED shows a champion maximum external quantum efficiency (EQE) of 9.35%, which is much better than that of phenylmethylamine (PMA) and phenylbutylamine (PBA) modified devices. For alkylamine-based devices, the maximum EQEs gradually rise from 2.72 to 6.33% and 6.66% as increase of alkyl chain length. PEA modified device exhibits the best half-lifetime of 114 min and alkylamine-based devices exhibit almost equal T 50 of approximately 20 min. X-ray diffraction measurements show that the dominant diffraction peaks of pervoskite films disappear or shift and scanning electron microscope detected that many pinholes appeared in perovskite films after operation. Combining with the results of X-ray photoelectron spectroscopy, we conclude that the recrystallization of perovskite occurred during the operation causes the film change in morphology and crystallinity, ultimately result in the degradation of PeLEDs.

A series of phosphinecarbonylpalladium and -nickel catalysts bearing various substituents on the ligand backbone were prepared, characterized, and used in ethylene polymerization and copolymerization with polar monomers. The Pd and Ni catalysts can achieve high activities as well as high polymer molecular weights in both ethylene polymerization and copolymerization with polar monomers. The electron-donating group from the carbonyl side can effectively increase the polymer molecular weights. Utilization of a cyclic backbone structure can increase the catalytic activities at the expense of the polymer molecular weights. Moreover, installation of a pyridyl moiety in the ligand backbone can enable Lewis acid responsiveness and can enhance the polymerization activities. These results suggest the importance of the ligand backbone for the properties of catalysts in ethylene polymerization and copolymerization reactions.

Fast development of cutting-edge areas including aviation and space, new energy, electrical and electronics industries asks for increasing requirements on heat resistant dielectric polymer nanocomposites with high dielectric constant (D K). This review focuses on recent research progress of thermally resistant polymer nanocomposites with high D K , which consists of four parts. In the first two parts, high D K nanocomposites based on thermally resistant thermoplastics and thermosetting resins are introduced, and then the effect of temperature on the dielectric properties of nanocomposites is discussed in the third part. In the last part, summary and future perspectives were provided.

Direct intramolecular aminoboration of sulfonamidoallenes was realized using BCl 3 as a boron source. The reactions benefited from the interaction between BCl 3 and sulfonamides and provided a variety of borylvinyl heterocycles in good isolated yields. When chiral substrates were involved in the reactions, high stereoselectivity was observed, as can be ascertained by singlecrystal X-ray diffraction experiments. Derivatization of the thus-obtained borylvinyl compounds proceeded readily, and different functionalities could be obtained via oxidation, halogenation, and Suzuki coupling reactions.

In quasi-two-dimensional (quasi-2D) perovskite films, carriers transport in the cascade structural systems involving various quantum wells (QWs) n, but their efficiency is limited by the severe nonradiative recombination within plentiful n = 1, 2, 3 domains induced by traditional ammonium bromide passivation. Here, we fabricate the quasi-2D films with the elimination of n = 1, 2, 3 domains by introducing the ionic liquid n-butylamine acetate (BAAc) instead of n-butylamine hydrobromide (BABr), which increases the photoluminescence quantum yield (PLQY) and lowers the surface roughness of films. Due to the anion exchange between BAAc and methylamine hydrobromide (MABr), BAAc exhibits a sole passivation effect on methylamine-based perovskites. As a result, the ionic liquid-derived perovskite light-emitting diodes (PeLEDs) display blue emission at 479 nm and show significantly improved performance on external quantum efficiency (EQE) and luminance. Our finding provides insights into the passivating effect of ionic liquid on quasi-2D perovskites and will benefit fabricating PeLEDs with enhanced performance.

No abstract

Thiourea and urea catalysts have received much attention in the field of ring-opening polymerization. In the (thio)urea/alkoxide catalytic system, sidearm groups can influence the catalytic performance of the organocatalyst moiety. In this work, a series of (thio)ureas bearing 2-, 3-and 4-pyridyl moieties were designed and synthesized. The (thio)ureas bearing a 2-pyridyl group exhibited much higher catalytic activities than the (thio)ureas bearing 3-or 4-pyridyl groups, suggesting a sidearm effect. Both crystal data and computational studies indicated that 2-pyridyl can form an intramolecular hydrogen bond with the NH moiety, resulting in a Brønsted base/Lewis acid bifunctional catalytic system. Furthermore, the catalyst was stimuli-responsive in Lewis acid/base-modulated ring-opening polymerization. Coordination between the Lewis acid BEt 3 and the catalyst was found to terminate the polymerization. Subsequently, the coordinated species was cleaved using the Lewis base bicyclo[2.2.2]-1,-4-diazaoctane, resulting in the reactivation of the catalyst.