Blue TADF Emitters Based on Indenocarbazole Derivatives with High Photoluminescence and Electroluminescence Efficiencies.

A series of blue thermally activated delayed fluorescence (TADF) emitters were designed and synthesized using 2,4,6-triphenyl-1,3,5-triazine as the acceptor unit and indenocarbazole derivatives as the electron-donating moiety. In contrast with other six-membered heterocycles, like phenothiazine, phenoxazine, and dihydroacridine, where the TADF efficiency is affected by the presence of different conformers, indenocarbazole derivatives do not show this effect. Therefore, InCz23FlTz, InCz23DPhTz, InCz23DMeTz, and InCz34DPhTz allow the investigation of the effect of different substituents and substitution positions on TADF properties, without the influence of different conformations. We have demonstrated that the substituted position on the carbazole and different substituents in the same position have clear influence on the donor character of indenocarbazole derivatives. Also, the color purity of blue emission and excited states could be adjusted by substituents and substituted position, and thus excellent blue emitters can be obtained. Besides, the four compounds show relatively small TADF contribution under optical excitation; however, excellent performances are obtained in the electroluminescent devices, especially with InCz34DPhTz, which shows a maximum external quantum efficiency of around 26%. In the end, we find an effective way to design high-efficiency blue TADF materials and deeply study the relation between the structure and property in indenocarbazole derivatives.

Radical-Based Organic Light-Emitting Diodes with Maximum External Quantum Efficiency of 10.6.

A new luminescent radical, tris-2,4,6-trichlorophenylmethyl-1,5-diazarcarbazole (TTM-DACz), was synthesized and characterized. The photoluminescence quantum yield of TTM-DACz in solid 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene matrix film (5 wt %) is as high as 57.0%. Organic light-emitting diodes (OLEDs) employing TTM-DACz as the emitter were fabricated. By rational design of the device structure and host-guest doping system, external quantum efficiency (EQE) of up to 10.6% of the optimized device with a red CIE chromaticity of (0.62, 0.36) was obtained, which is among the highest values for red OLEDs using nonphosphorescent materials as the emitters. This work will accelerate the development of luminescent radical materials for high-performance OLEDs.

Fabrication of high-performance MXene-based all-solid-state flexible microsupercapacitor based on a facile scratch method.

MXenes have emerged as promising electrode materials for microsupercapacitors (MSCs) owing to their high volumetric and areal capacitances. In addition to the development of novel electrode materials, fabrication of interdigital electrodes is another key to realize high-performance MSCs. Herein, we demonstrate the patterning of few-layered Ti3C2T x nanosheets on various substrates for MSCs by a facile, fast, and nearly zero-cost 'scratch' strategy. The fabricated Ti3C2T x -based all-solid-state MSC achieves a high areal capacitance of 25.5 mF cm-2, which benefits from the unique layered structure and high electrical conductivity of the electrode. The fabricated planar MSC also delivers good cycling stability and excellent flexibility. Moreover, our fabrication strategy can be readily extended to other composite films for MSCs and become potential micropower sources for miniaturized electronic devices.

Boosting Lithium Storage Properties of MOF Derivatives through a Wet-Spinning Assembled Fiber Strategy.

Graphene composite fibers are of great importance in constructing electrode materials with high flexibility and conductivity for energy storage and electronic devices. Integration of multifunctional metal-organic frameworks (MOFs) into graphene fiber scaffolds enables novel functions and enhanced physical/chemical properties. The close-packed and aligned graphene sheets along with the porous MOF-derived structures can achieve excellent lithium storage performance through synergetic effects. In this work, a facile and general strategy is demonstrated for the preparation of MOF/graphene oxide (GO) fibers, which serve as precursors for the subsequent preparation of porous metal oxide/reduced graphene oxide (rGO) composite fibers. The obtained composites, for example, porous Fe2 O3 /rGO and Co3 O4 /rGO fibers, possess unique features of MOF-derived porous structures and excellent electrical conductivity. When tested as anode materials for lithium-ion batteries in coin cells, the MOF/GO fiber-derived porous metal oxide/rGO composite fibers exhibited high specific capacity, excellent rate capability and cycling performance. Moreover, a flexible fiber battery was fabricated based on the Fe2 O3 /rGO composite fiber, which demonstrates its potential application for flexible electronic devices.