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Metal halide perovskite quantum dots (QDs) and polymer composite films have witnessed extensive investigation in flexible optoelectronic devices, while the unsatisfactory environmental and mechanical properties of the composite films set substantial limitations for practical applications. Herein, highly luminescent perovskite QDs-polymer composite films (QPFs) are fabricated with remarkable environmental and mechanical stabilities by incorporation of perovskite QDs into fluoroelastomer polymeric matrix. The stretchable QPFs show excellent self-healing ability with micron-and centimeter-scale cracks healed in dozens of minutes and hours, respectively, due to the strong dipole-dipole interaction between the CF bonds of fluoroelastomer. After careful optimization of QDs ratios, a flat and smooth film morphology is achieved with a uniform distribution of QDs, which promotes good optical properties with a long PL lifetime of 1213.75 ns and high photoluminescence quantum yields up to 96.1%, and super environmental and mechanical stability These merits of QPFs enable their practical applications in flexible white light-emitting devices and wide color gamut displays with 124% of standard National Television Standards Committee and 96% of Recommendation 2020, respectively, exhibiting vivid pictures with high saturations for the object colors, indicating great potential toward practical applications.

In this article, two novel microstrip band-stop filters using the gradually variational stepped impedance hairpin resonator with DGS or not are presented. By using the gradually variational stepped impedance hairpin resonator, the filters have remarkable advantages, such as compact size, simple structure, and high selectivity. Two band-stop filters are designed, fabricated, and measured. The measurement results show good agreement with the simulation ones. ACKNOWLEDGMENTSThis work was supported by National Natural Science Foundation of China under Grant 61171051. The authors would like to thank the persons in Agilent Open Laboratory in Beijing, for their technical assistance. ABSTRACT: This article addresses the physical realization of crosscoupled waveguide filters based on electromagnetic (EM) simulations. For this design procedure, the filter structure is simulated by successively adding one resonator at a time. The desired filter response is achieved without the need of a global optimisation on all the mechanical dimensions within an EM simulator. This reduces the design time required for a crosscoupled waveguide filter and allows the possibility of building high-order waveguide filters with complex crosscouplings. A sixth order X-band dual-band filter with a center frequency of 10 GHz and a fractional bandwidth of 1% is designed using this procedure and presented here as an example. Excellent agreement between simulation results and theoretical results from coupling matrix verifies the proposed approach. THE DESIGN OF WAVEGUIDE FILTERS BASED ON CROSS-COUPLED RESONATORS

perovskite has exhibited great potential to be an ideal luminescent material for perovskite light-emitting diodes (PeLEDs). However, the loworder phases (especially n = 1 phase) and the inevitable defects result in massive nonradiative recombination and poor emission efficiency. Herein, a multifunctional molecule of tetrabutylammonium dihydrogen phosphate (TDP) is introduced to simultaneously suppress the low-n phase, passivate the defects, and increase the exciton binding energy of the quasi-2D perovskite for massive radiative recombination and thus high emission efficiency. The multifunctional roles of TDP are realized by the synergistic effects of tetrabutylammonium cation and dihydrogen phosphate anion, both of which show strong interaction with the lead bromide octahedron of the perovskite. As a result, the TDP-incorporated perovskite films show a great enhancement of the emission efficiency with a remarkable increase in photoluminescence quantum yield (PLQY) from 34.6 to 96.9% at the wavelength of 522 nm. The strengthened radiative recombination promotes efficient emission efficiency with over 2.5-fold improvement in external quantum efficiency (EQE) and current efficiency (CE) from 3.27% and 10.83 cd A −1 to 9.25% and 28.35 cd A −1 , respectively, as well as high brightness with over 37% enhancement from 12713 to 17536 cd m −2 . Consequently, this work contributes to an efficient approach to employ a multifunctional molecule for highly emissive quasi-2D perovskites and enhanced quasi-2D PeLED performances.

Multi‐shelled ZnSeTe/ZnSe/ZnS quantum dots (QDs) have served as a promising eco‐friendly emitter for blue quantum dot light‐emitting diodes (QLEDs). While extensive studies have concentrated on the optimization of the shell species and thickness of the multi‐shelled QDs to raise the QLED electroluminescent performance, very few reports focus on the QD surface states involving ligand and defect modulations which are essential for high‐performance QLEDs. Herein, the strategy of bromide decoration is theoretically and practically demonstrated to simultaneously diminish the QD surface defects by passivating the unsaturated Zn for strengthened carrier radiative recombination and removing the superabundant oleic acid through ligand exchange for efficient carrier transport. As a result, the merits of bromide decoration benefit a large increase in photoluminescence quantum yield (PLQY) from 39.7% to 86.2% at the wavelength of 443 nm, as well as a great enhancement of the device performance with over sevenfold improvement in external quantum efficiency (EQE) from 0.74% to 5.46% and a distinct decrease in turn‐on voltage from 6.7 to 5.9 V. Consequently, this work contributes an effective approach of the multi‐shelled QD surface decoration toward enhanced QLED performance.