Cl incorporation has been reported to be able to significantly increase the diffusion length of carriers in organo-lead halide perovskite thin films. However, due to the low solubility of PbCl₂, Cl incorporation has been rarely reported in a two-step process, which is capable of producing uniform organo-lead halide perovskite thin films. In this letter, we report a novel growth method that combines the two-step process and Cl incorporation. The Cl-incorporated organo-lead halide perovskite solar cell made from a two-step process demonstrated a power conversion efficiency of 10.5%, which is 27% higher than that without Cl incorporation. Further investigation was performed to explore the fundamentals of the enhancement. Kelvin probe force microscopy (KPFM) measurement revealed a larger band bending at grain boundaries with Cl incorporation, which brings the Fermi level of the bulk perovskite thin film closer to the center of the bandgap. As a result, a p–i–n type of junction is formed in the devices with Cl incorporation, which facilitates the charge carrier collection. Additional carrier lifetime measurements indicate that the electron lifetime in the perovskite thin film with Cl incorporation is longer, indicating reduced recombination in the devices with Cl incorporation.

It has been clinically proven that exoskeletons are effective self-training rehabilitation or daily living assistance devices for patients with hand dysfunctions. However, exoskeleton-assisted hand exercises with high degrees-of-freedom are considered as challenging tasks because the digit space, especially the thumb, cannot accommodate enough actuators. In this article, we report a tendon-driven soft hand exoskeleton with a hybrid configuration for thumb actuation. The soft hand exoskeleton system uses the least number of actuators to realize full degrees-of-freedom actuation for all digits. It is tested on a stroke patient with hemiplegia and a healthy subject. The experimental results show that the hand exoskeleton could assist the stroke patient to accomplish various training tasks, such as thumb encircling, grasping, pinching, releasing, and writing. It was found that digit trajectories and joint angle changes of the stroke patient were close to those of the healthy subject. Especially, the range of motion of the stroke patient shows significant improvement with the hand exoskeleton assistance compared to that without the hand exoskeleton assistance. The research in this article paves the way to develop fully actuated soft hand exoskeleton that can be eventually integrated with an electroencephalogram or electromyography for self-training rehabilitation or daily living assistance.

The single-pass scan Kelvin probe force microscopy (KPFM) in ambient condition has a few advantages over the dual-pass lift-up scan KPFM. For example, its spatial resolution is expected to be higher; and its topographical errors caused by electrostatic forces are minimized because electrostatic forces are actively suppressed during the simultaneous topographical and KPFM measurement. Because single-pass scan KPFM in ambient condition is relatively new, it received little attention in the literature so far. In this article, we discuss several major practical aspects of single-pass scan KPFM especially in ambient condition. First, we define the resolution using a point spread function. With this definition, we analyze the relation between the resolution and the scanning parameters such as tip apex radius and tip-surface distance. We further study the accuracy of KPFM based on the point spread function. Then, we analyze the sensitivity of KPFM under different operation modes. Finally, we investigate the crosstalk between the topographical image and the surface potential image and demonstrate the practical ways to minimize the crosstalk. These discussions not only help us to understand the single-pass scan KPFM but also provide practical guidance in using single-pass scan KPFM.