Beihang University

About: Beihang University is a education organization based out in Beijing, China. It is known for research contribution in the topics: Computer science & Control theory. The organization has 67002 authors who have published 73507 publications receiving 975691 citations. The organization is also known as: Beijing University of Aeronautics and Astronautics.

Recent Advances in Wide-Bandgap Photovoltaic Polymers

Abstract: The past decade has witnessed significant advances in the field of organic solar cells (OSCs). Ongoing improvements in the power conversion efficiency of OSCs have been achieved, which were mainly attributed to the design and synthesis of novel conjugated polymers with different architectures and functional moieties. Among various conjugated polymers, the development of wide-bandgap (WBG) polymers has received less attention than that of low-bandgap and medium-bandgap polymers. Here, we briefly summarize recent advances in WBG polymers and their applications in organic photovoltaic (PV) devices, such as tandem, ternary, and non-fullerene solar cells. Addtionally, we also dissuss the application of high open-circuit voltage tandem solar cells in PV-driven electrochemical water dissociation. We mainly focus on the molecular design strategies, the structure-property correlations, and the photovoltaic performance of these WBG polymers. Finally, we extract empirical regularities and provide invigorating perspectives on the future development of WBG photovoltaic materials.

Pearson's Principle Inspired Generalized Strategy for the Fabrication of Metal Hydroxide and Oxide Nanocages

Abstract: Designing a general route for rational synthesis of a series or families of nanomaterials for emerging applications has become more and more fascinating and vital in the view of nanoscience and nanotechnology. Herein, we explore a general strategy for fabricating uniform nanocages of metal hydroxides (MHs) and metal oxides (MOs). A template-assisted route inspired by Pearson’s hard and soft acid–base (HSAB) principle was employed for synthesizing MH nanocages via meticulous selection of the coordinating etchant as well as optimization of the reaction conditions. The concept of “coordinating etching” is successfully achieved in this work. This unique route shows potential in designing well-defined and high-quality MH nanocages with varying components, shell thicknesses, shapes, and sizes at room temperature. Consequently, porous MO nanocages can be obtained readily just through appropriate thermal treament of the respective MH nanocages. The overall strategy present in this work extends the application of ...

Facile synthesis of Li2S–polypyrrole composite structures for high-performance Li2S cathodes

Abstract: Li2S is an attractive prelithiated cathode material with a high theoretical capacity of 1166 mA h g−1, which is far above that of its transition metal oxide/phosphate counterparts. Here, we demonstrate facile, in situ synthesis of Li2S–polypyrrole composites for use as high-performance Li2S cathodes. The N atoms in polypyrrole were found to possess favorable Li–N interaction with Li2S, which enables polypyrrole to bind strongly onto and cover the surface of Li2S to constrain intermediate polysulfides during cycling. Polypyrrole, being a conducting polymer, also helps to facilitate electronic conduction. Using the Li2S–polypyrrole composites as a cathode material, we demonstrate a high discharge capacity of 785 mA h g−1 of Li2S (∼1126 mA h g−1 of S) with stable cycling over prolonged 400 charge/discharge cycles.

Adaptive Trajectory Tracking Control of a Fully Actuated Surface Vessel With Asymmetrically Constrained Input and Output

Abstract: This brief addresses the trajectory tracking control problem of a fully actuated surface vessel subjected to asymmetrically constrained input and output. The controller design process is based on the backstepping technique. An asymmetric time-varying barrier Lyapunov function is proposed to address the output constraint. To overcome the difficulty of nondifferentiable input saturation, a smooth hyperbolic tangent function is employed to approximate the asymmetric saturation function. A Nussbaum function is introduced to compensate for the saturation approximation and ensure the system stability. The command filters and auxiliary systems are integrated with the control law to avoid the complicated calculation of the derivative of the virtual control in backstepping. In addition, the bounds of uncertainties and disturbances are estimated and compensated with an adaptive algorithm. With the proposed control, the constraints will never be violated during operation, and all system states are bounded. Simulation results and comparisons with standard method illustrate the effectiveness and advantages of the proposed controller.

Optimized Fibril Network Morphology by Precise Side-Chain Engineering to Achieve High-Performance Bulk-Heterojunction Organic Solar Cells.

Abstract: A polymer fibril assembly can dictate the morphology framework, in forming a network structure, which is highly advantageous in bulk heterojunction (BHJ) organic solar cells (OSCs). A fundamental understanding of how to manipulate such a fibril assembly and its influence on the BHJ morphology and device performance is crucially important. Here, a series of donor-acceptor polymers, PBT1-O, PBT1-S, and PBT1-C, is used to systematically investigate the relationship between molecular structure, morphology, and photovoltaic performance. The subtle atom change in side chains is found to have profound effect on regulating electronic structure and self-assembly of conjugated polymers. Compared with PBT1-O and PBT1-S, PBT1-C-based OSCs show much higher photovoltaic performance with a record fill factor (FF) of 80.5%, due to the formation of optimal interpenetrating network morphology. Such a fibril network strategy is further extended to nonfullerene OSCs using a small-molecular acceptor, which shows a high efficiency of 12.7% and an FF of 78.5%. The results indicate the formation of well-defined fibrillar structure is a promising approach to achieving a favorable morphology in BHJ OSCs.