Anomalously large interface charge in polarity-switchable photovoltaic devices indicates the large amount of mobile ions in organic–inorganic halide perovskites.
While perovskite light-emitting diodes typically made with high work function anodes and low work function cathodes have recently gained intense interests. Perovskite light-emitting devices with two high work function electrodes with interesting features are demonstrated here. Firstly, electroluminescence can be easily obtained from both forward and reverse biases. Secondly, the results of impedance spectroscopy indicate that the ionic conductivity in the iodide perovskite (CH3 NH3PbI3) is large with a value of approximate to 10(-8) S cm(-1). Thirdly, the shift of the emission spectrum in the mixed halide perovskite (CH3NH3PbI3-Br-x(x)) light-emitting devices indicates that I(-)ions are mobile in the perovskites. Fourthly, this work shows that the accumulated ions at the interfaces result in a large capacitance (approximate to 100 mu F cm(-2)). The above results conclusively prove that the organic-inorganic halide perovskites are solid electrolytes with mixed ionic and electronic conductivity and the light-emitting device is a light-emitting electrochemical cell. The work also suggests that the organic-inorganic halide perovskites are potential energy-storage materials, which may be applicable in the field of solid-state supercapacitors and batteries
Deep learning has achieved remarkable results in many computer vision tasks. Deep neural networks typically rely on large amounts of training data to avoid overfitting. However, labeled data for realworld applications may be limited. By improving the quantity and diversity of training data, data augmentation has become an inevitable part of deep learning model training with image data. As an effective way to improve the sufficiency and diversity of training data, data augmentation has become a necessary part of successful application of deep learning models on image data. In this paper, we systematically review different image data augmentation methods. We propose a taxonomy of reviewed methods and present the strengths and limitations of these methods. We also conduct extensive experiments with various data augmentation methods on three typical computer vision tasks, including semantic segmentation, image classification and object detection. Finally, we discuss current challenges faced by data augmentation and future research directions to put forward some useful research guidance.
C. Liang, Z. He, W. C. H. Choy, and co‐workers demonstrate on page 7226 a new type of perovskite device: perovskite light‐emitting electrochemical cells. Organic–inorganic halide perovskites used as solid electrolytes are shown to have an ionic conductivity comparable to polymer electrolytes, which is important for understanding the operation mechanisms and electrical properties of perovskite devices. This suggests future applications for perovskites in energy storage devices.
β-amino triphenylenes can be accessed via palladium catalyzed amination of the corresponding triflate using benzophenone imine. Transformation of amine 6 to benzoyl amide 18 is also straightforward and its wide mesophase range demonstrates that the new linkage supports columnar liquid crystal formation. Amine 6 also undergoes clean aerobic oxidation to give a new twinned structure linked through an electron-poor pyrazine ring. The new discotic liquid crystal motif contains donor and acceptor fragments, and is more oval in shape rather than disk-like. It forms a wide range columnar mesophase. Absorption spectra are strong and broad; emission is also broad and occurs with a Stokes shift of ca. 0.7 eV, indicative of charge-transfer character.Discotic liquid crystals have attracted considerable attention from both a theoretical and applications point of view.1 Two general classes of liquid crystal phase are formed from discshaped molecules. Columnar phases are formed when the individual molecules stack on top of each other and the lattice arrangement of the resulting columns defines the sub-class of mesophase.2 Columnar phases are important because the stacking arrangement provides π-overlap in one direction only, leading to 1D conduction of charge and/or energy.3 Nematic phases, 4 where the molecules retain orientational order only, are much rarer, but also find important applications, most notably as optical compensating films in LCDs.
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