Electrochemical stripping features of graphite and its products characterization

A stable dispersion in mixed solvent of water and N,N-dimethyl formamide (DMF) of graphene was synthesized by one-step electrochemical approach. Here we demonstrate about electrochemical stripping graphite to prepare graphene influence by different electrolytes. The physical and chemical properties of the stripping product had been characterized by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), UV-Vis spectrophotometer (UV-Vis), Scanning electron microscopy (SEM), Transmission Electron Microscope (TEM) . The characteristic results of XRD showed that it could improve the efficiency of graphite stripping when H₂SO₄ was used as electrolyte mother liquid and amount of HNO₃ was doped in electrolyte; XPS and FTIR results indicate that the electrochemical stripping products preserve the intrinsic structure of graphene. The results of SEM and TEM shown that the surface morphology of the as-prepared graphene was folded lamellar structure and have good transparency;its thickness varies from 0.8 nm to a few nanometers.     

Reducing Hysteresis and Enhancing Performance of Perovskite Solar Cells Using Low‐Temperature Processed Y‐Doped SnO2 Nanosheets as Electron Selective Layers

Despite the rapid increase of efficiency, perovskite solar cells (PSCs) still face some challenges, one of which is the current–voltage hysteresis. Herein, it is reported that yttrium‐doped tin dioxide (Y‐SnO₂) electron selective layer (ESL) synthesized by an in situ hydrothermal growth process at 95 °C can significantly reduce the hysteresis and improve the performance of PSCs. Comparison studies reveal two main effects of Y doping of SnO₂ ESLs: (1) it promotes the formation of well‐aligned and more homogeneous distribution of SnO₂ nanosheet arrays (NSAs), which allows better perovskite infiltration, better contacts of perovskite with SnO₂ nanosheets, and improves electron transfer from perovskite to ESL; (2) it enlarges the band gap and upshifts the band energy levels, resulting in better energy level alignment with perovskite and reduced charge recombination at NSA/perovskite interfaces. As a result, PSCs using Y‐SnO₂ NSA ESLs exhibit much less hysteresis and better performance compared with the cells using pristine SnO₂ NSA ESLs. The champion cell using Y‐SnO₂ NSA ESL achieves a photovoltaic conversion efficiency of 17.29% (16.97%) when measured under reverse (forward) voltage scanning and a steady‐state efficiency of 16.25%. The results suggest that low‐temperature hydrothermal‐synthesized Y‐SnO₂ NSA is a promising ESL for fabricating efficient and hysteresis‐less PSC.     

浅谈屏蔽盒校准问题

自从无线电通信和电报通信问世以来,电磁环境已成为人类生存环境中不可或缺的组成部分。一些有意的和非有意的源所产生的电磁能量会对它们周围很多电气与电子设备产生干扰,影响它们正常工作。在手机进行研发、生产、维修的过程中,需要对手机进行功率准确度及灵敏度方面进行测试,如果受到外界其他干扰源的干扰,很容易导致手机性能测试的不准确。为了保证手机测试的过程中不受其他外界干扰,普遍使用屏蔽盒来有效地屏蔽外界电磁辐射对手机测试过程中产生的种种影响。屏蔽效能是屏蔽盒性能好坏的一项重要指标参数,如何去测量屏蔽盒的屏蔽效能就显得尤为重要。本文通过研究屏蔽效能测量的方法和原理,提出合理的测量方法。     

Patterning of Discotic Liquid Crystals with Tunable Molecular Orientation for Electronic Applications

The large‐area formation of functional micropatterns with liquid crystals is of great significance for diversified applications in interdisciplinary fields. Meanwhile, the control of molecular alignment in the patterns is fundamental and prerequisite for the adequate exploitation of their photoelectric properties. However, it would be extremely complicated and challenging for discotic liquid crystals (DLCs) to achieve the goal, because they are insensitive to external fields and surface chemistry. Herein, a simple method of patterning and aligning DLCs on flat substrates is disclosed through precise control of the formation and dewetting of the capillary liquid bridges, within which the DLC molecules are confined. Large‐area uniform alignment occurs spontaneously due to directional shearing force when the solvent is slowly evaporated and programmable patterns could be directly generated on desired substrates. Moreover, the in‐plane column direction of DLCs is tunable by slightly tailoring their chemical structures which changes their self‐assembly behaviors in liquid bridges. The patterned DLCs show molecular orientation–dependent charge transport properties and are promising for templating self‐assembly of other materials. The study provides a facile method for manipulation of the macroscopic patterns and microscopic molecular orientation which opens up new opportunities for electronic applications of DLCs.