Efficient CsPbBr3 Perovskite Light-Emitting Diodes via Novel Multi-Step Ligand Exchange Strategy Based on Zwitterionic Molecules.

Perovskite nanocrystals have absorbed increasing interest, especially in the field of optoelectronics, owing to their unique characteristics, including their tunable luminescence range, robust solution processability, facile synthesis, and so on. However, in practice, due to the inherent instability of the traditional long-chain insulating ligands surrounding perovskite quantum dots (PeQDs), the performance of the as-fabricated QLED is relatively disappointing. Herein, the zwitterion 3-(decyldimethylammonio)propanesulfonate (DLPS) with the capability of double passivating perovskite quantum dots could effectively replace the original long-chain ligand simply through a multistep post-treatment strategy to finally inhibit the formation of defects. It was indicated from theexperimental results that the DLPS, as one type of ligand with the bimolecular ion, was very adavntageous in replacing long-chain ligands and further suppressing the formation of defects. Finally, the perovskite quantum dots with greatly enhanced PLQY as high as 98% were effectively achieved. Additionally, the colloidal stability of the corresponding PeQDs has been significantly enhanced, and a transparent colloidal solution was obtained after 45 days under ambient conditions. Finally, the as-fabricated QLEDs based on the ligand-exchanged PeQDs exhibited a maximum brightness of 9464 cd/m2 and an EQE of 12.17%.

Superstructure MOF as a framework to composite MoS2 with rGO for Li/Na-ion battery storage with high-performance and stability.

Metal sulfides, one kind of electrode material with very high theoretical capacity, have been widely studied for use in lithium and sodium ion batteries. However, there are some problems hindering their applications in electrodes, such as low conductivity and volume expansion. The MOF introduces metals with different coordination strengths into an existing MOF structure, which improves the performance of the electrode to a certain extent. In this paper, Fe/Zn bimetallic MOF rod-like superstructure was prepared based on Ostwald theory. Accompanied by sulfuration, the MOF was effectively combined with MoS2 and GO, and the objective materials Fe7S8-C/ZnS-C@MoS2/rGO composites were successfully prepared. The MOF material provides a good frame and an efficient electron transport path, while the robust rGO wall effectively inhibits the pulverization of materials during the lithium/sodium intercalation/escalation courses. This particular material exhibited excellent cycling and rate capability performance when used in Li/Na-ion batteries. When used in Li-batteries, the electrode material delivered a specific capacity of 1598.3 mA h g-1 at 0.1 A g-1 and remained at 1196.7 mA h g-1 even after about 100 cycles and further exhibited a specific capacity of 368.68 mA h g-1 at the current rate of 5 A g-1 even after 1000 cycles, respectively. As for sodium batteries, these electrode materials exhibited an initial reversible capacity of 1053.6 mA h g-1 at 0.1 A g-1 and the reversible capacity was still as high as 592.2 mA h g-1 after 200 cycles. It is perhaps that this composite material with its particular architecture and composition is greatly beneficial for electron transfer and Li/Na ion diffusion. In the repeated physicochemical/nutrifying process, the appropriate distance between adjacent MOFs is of great help in preventing volume changes and thus improving the electrochemical performance.