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Organic–inorganic hybrid halide perovskite materials have attracted enormous interest in recent years due to their excellent photovoltaic properties, which are strongly limited by their instability. Solar cells based on the inorganic perovskite materials have been developed rapidly and exhibit excellent stability. The crystalline quality and composition of the perovskite layer play the key role in the efficiency of solar cells. Among the various film deposition techniques, pulsed laser deposition has the distinctive advantages of preparation of thin films of high crystalline quality and close duplication of the composition of the targets. In the work, we applied pulsed laser deposition to prepare a CsPbBr3 thin film that displays good stability in a high-humidity environment. Single crystalline CsPbBr3 powders were grown first by a solution method to prepare the target. The CsPbBr3 plasma produced by focused pulsed laser can permeate into the mesoporous TiO2 layer and distribute uniformly inside. The thickness of mesoporous TiO2 and CsPbBr3 layers has a critical influence on device performance. The device with optimization of the layer thickness can achieve the highest power conversion efficiency of 6.3%.

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Tuning the Fermi level (EF) in Bi2Te3 topological-insulator (TI) films is demonstrated on controlling the temperature of growth with molecular-beam epitaxy (MBE).

Ultrathin bilayers (BLs) of bismuth have been predicated to be a two-dimensional (2D) topological insulator. Here we report on a new route to manufacture the high-quality Bi bilayers from a 3D topological insulator, a top-down approach to prepare large-area and well-ordered Bi(111) BL with deliberate hydrogen etching on epitaxial Bi2Se3 films. With scanning tunneling microscopy (STM) and X-ray photoelectron spectra (XPS) in situ, we confirm that the removal of Se from the top of a quintuple layer (QL) is the key factor, leading to a uniform formation of Bi(111) BL in the van der Waals gap between the first and second QL of Bi2Se3. The angle resolved photoemission spectroscopy (ARPES) in situ and complementary density functional theory (DFT) calculations show a giant Rashba splitting with a coupling constant of 4.5 eV Å in the Bi(111) BL on Bi2Se3. Moreover, the thickness of Bi BLs can be tuned by the amount of hydrogen exposure. Our ARPES and DFT study indicated that the Bi hole-like bands increase with increasing the Bi BL thickness. The selective hydrogen etching is a promising route to produce a uniform ultrathin 2D topological insulator (TI) that is useful for fundamental investigations and applications in spintronics and valleytronics.

This paper presents the design, dynamic modeling and motion control of a novel cable-driven upper limb robotic exoskeleton for a rehabilitation exercising. The proposed four degree-of-freedom robotic exoskeleton, actuated by pneumatic artificial muscle actuators, is characterized by a safe, compact, and lightweight structure, complying with the motion of an upper limb as close as possible. In order to perform a passive rehabilitation exercise, the dynamic models were developed by the Lagrange formulation in terms of quasi coordinates combined with the virtual work principle, and then the adaptive fuzzy sliding mode control was designed for the rehabilitation trajectory control. Finally, rehabilitation experiments were conducted to validate the prototype of upper limb robotic exoskeleton and the controller design. INDEX TERMS Pneumatic artificial muscle, robotic exoskeleton, rehabilitation, adaptive fuzzy sliding mode control.

Adaptive optics techniques have been developed over the past half century and routinely used in large ground-based telescopes for more than 30 years. Although this technique has already been used in various applications, the basic setup and methods have not changed over the past 40 years. In recent years, with the rapid development of artificial intelligence, adaptive optics will be boosted dramatically. In this paper, the recent advances on almost all aspects of adaptive optics based on machine learning are summarized. The state-of-the-art performance of intelligent adaptive optics are reviewed. The potential advantages and deficiencies of intelligent adaptive optics are also discussed.