Morphology Transformation Pathway of Block Copolymer-Directed Cooperative Self-Assembly of ZnO Hybrid Films Monitored In Situ during Slot-Die Coating

Cooperative self-assembly (co-assembly) of diblock copolymers (DBCs) and inorganic precursors that takes inspiration from the rich phase separation behavior of DBCs can enable the realization of a broad spectrum of functional nanostructures with the desired sizes. In a DBC assisted sol–gel chemistry approach with polystyrene-block-poly(ethylene oxide) and ZnO, hybrid films are formed with slot-die coating. Pure DBC films are printed as control. In situ grazing-incidence small-angle X-ray scattering measurements are performed to investigate the self-assembly and co-assembly process during the film formation. Combining complementary ex situ characterizations, several distinct regimes are differentiated to describe the morphological transformations from the initially solvent-dispersed to the ultimately solidified films. The comparison of the assembly pathway evidences that the key step in the establishment of the pure DBC film is the coalescence of spherical micelles toward cylindrical domains. Due to the presence of the phase-selective precursor, the formation of cylindrical aggregates in the solution is crucial for the structural development of the hybrid film. The pre-existing cylinders in the ink impede the domain growth of the hybrid film during the subsequent drying process. The precursor reduces the degree of order, prevents crystallization of the PEO block, and introduces additional length scales in the hybrid films.     

<Emphasis Type="Italic">In situ</Emphasis> grazing-incidence small-angle X-ray scattering observation of block-copolymer templated formation of magnetic nanodot arrays and their magnetic properties

The fabrication of bit-patterned media (BPM) is crucial for new types of hard disk drives.The development of methods for the production of BPM is progressing rapidly.Conventional lithography reaches the limit regarding lateral resolution,and new routes are needed.In this study,we mainly focus on the dependence of the size and shape of magnetic nanodots on the Ar+-ion etching duration,using silica dots as masks.Two-dimensional (2D) arrays of magnetic nanostructures are created using silica-filled diblock-copolymer micelles as templates.After the self-assembly of the micelles into 2D hexagonal arrays,the polymer shell is removed,and the SiO2 cores are utilized to transform the morphology into a (Co/Pt)2-multilayer via ion etching under normal incidence.The number of preparation steps is kept as low as possible to simplify the formation of the nanostructure arrays.High-resolution in situ grazing-incidence small-angle X-ray scattering (GISAXS) investigations are performed during the Ar+-ion etching to monitor and control the fabrication process.The in situ investigation provides information on how the etching conditions can be improved for further ex situ experiments.The GISAXS patterns are compared with simulations.We observe that the dots change in shape from cylindrical to conical during the etching process.The magnetic behavior is studied by utilizing the magneto-optic Kerr effect.The Co/Pt dots exhibit different magnetic behaviors depending on their size,interparticle distance,and etching time.They show ferromagnetism with an easy axis of magnetization perpendicular to the film.A systematic dependence of the coercivity on the dot size is observed.     

Critical Influence of Organic A′-Site Ligand Structure on 2D Perovskite Crystallization

Organic A′-site ligand structure plays a crucial role in the crystal growth of 2D perovskites, but the underlying mechanism has not been adequately understood. This problem is tackled by studying the influence of two isomeric A′-site ligands, linear-shaped n-butylammonium (n-BA⁺) and branched iso-butylammonium (iso-BA⁺), on 2D perovskites from precursor to device, with a combination of in situ grazing-incidence wide-angle X-ray scattering and density functional theory. It is found that branched iso-BA⁺, due to the lower aggregation enthalpies, tends to form large-size clusters in the precursor solution, which can act as pre-nucleation sites to expedite the crystallization of vertically oriented 2D perovskites. Furthermore, iso-BA⁺ is less likely to be incorporated into the MAPbI₃ lattice than n-BA⁺, suppressing the formation of unwanted multi-oriented perovskites. These findings well explain the better device performance of 2D perovskite solar cells based on iso-BA⁺ and elucidate the fundamental mechanism of ligand structural impact on 2D perovskite crystallization.     

Highly Tunable Nanostructures in a Doubly pH-Responsive Pentablock Terpolymer in Solution and in Thin Films

Multiblock copolymers with charged blocks are complex systems that show great potential for enhancing the structural control of block copolymers. A pentablock terpolymer PMMA-b-PDMAEMA-b-P2VP-b-PDMAEMA-b-PMMA is investigated. It contains two types of midblocks, which are weak cationic polyelectrolytes, namely poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and poly(2-vinylpyridine) (P2VP). Furthermore, these are end-capped with short hydrophobic poly(methyl methacrylate) (PMMA) blocks in dilute aqueous solution and thin films. The self-assembly behavior depends on the degrees of ionization α of the P2VP and PDMAEMA blocks, which are altered in a wide range by varying the pH value. High degrees of ionization of both blocks prevent structure formation, whereas microphase-separated nanostructures form for a partially charged and uncharged state. While in solutions, the nanostructure formation is governed by the dependence of the P2VP block solubility of the and the flexibility of the PDMAEMA blocks on α, in thin films, the dependence of the segregation strength on α is key. Furthermore, the solution state plays a crucial role in the film formation during spin-coating. Overall, both the mixing behavior of the 3 types of blocks and the block sequence, governing the bridging behavior, result in strong variations of the nanostructures and their repeat distances.     

高效透射光栅谱仪的初步研究

描述了一种新型透射光栅谱仪的结构和初步的实验结果。该谱仪由掠入射前置光学系统和大面积透射光栅组成，初步实验表明有可能研制成高效、高分辨的透射光栅谱仪。     

Benzoyl side-chains push the open-circuit voltage of PCDTBT/PCBM solar cells beyond 1 V

The synthesis, characterization and solar cell performance of PCDTBT and its highly soluble analogue hexyl-PCDTBT with cross-conjugated benzoyl moieties at the carbazole comonomer are presented. Through the use of both model reactions and time-controlled microwave-assisted Suzuki polycondensation, the base-induced cleavage of the benzoyl group from the polymer backbone has been successfully suppressed. Compared to the commonly used symmetrically branched alkyl motif, the benzoyl substituent lowers the energy levels of PCDTBT as well as the band gap, and consequently increases energy of the charge transfer state in blends with PC₇₁BM. As a result, photovoltaic diodes with high-open circuit voltage of above 1 V are realized.     

应用边界元法模拟厅堂中座席低谷效应

座席低谷效应是坐席中声波为掠入射时声场在低频段出现的选择性吸收的现象，它会影响厅堂中低频声的听感。文章用边界元法模拟了坐席低谷效应，考查影响座席低谷效应的因素。计算结果表明了坐席低谷效应在座席不同位置处的变化情况。最后列举了一些降低座席低谷效应的办法。     

Enhancing Crystallization in Hybrid Perovskite Solar Cells Using Thermally Conductive 2D Boron Nitride Nanosheet Additive

Controlling crystallization and grain growth is crucial for realizing highly efficient hybrid perovskite solar cells (PSCs). In this work, enhanced PSC photovoltaic performance and stability by accelerating perovskite crystallization and grain growth via 2D hexagonal boron nitride (hBN) nanosheet additives incorporated into the active perovskite layer are demonstrated. In situ X-ray scattering and infrared thermal imaging during the perovskite annealing process revealed the highly thermally conductive hBN nanosheets promoted the phase conversion and grain growth in the perovskite layer by facilitating a more rapid and spatially uniform temperature rise within the perovskite film. Complementary structural, physicochemical, and electrical characterizations further showed that the hBN nanosheets formed a physical barrier at the perovskite grain boundaries and the interfaces with charge transport layers, passivating defects, and retarding ion migration. As a result, the power conversion efficiency of the PSC is improved from 17.4% to 19.8%, along with enhanced device stability, retaining ≈90% of the initial efficiency even after 500 h ambient air storage. The results not only highlight 2D hBN as an effective additive for PSCs but also suggest enhanced thermal transport as one of the pathways for improved PSC performance by 2D material additives in general.     

高重频声光调Q掠入射激光器的掠入射角度优化

为了实现了高重复频率声光调Q运转,通过分析掠入射激光器中的等效抽运光模式,对掠入射激光器的掠入射角度进行了优化,获得重复频率大于2MHz的声光调Q TEM00基模的实验输出.理论分析和实验结果表明,掠入射激光器存在一个优化的掠入射角度可以获得尽量小的抽运光模式横截面积,有利于激光器获得高增益和实现高重频运转.