Lin Zhu

Abstract Solution-processed metal halide perovskites have been recognized as one of the most promising semiconductors, with applications in light-emitting diodes (LEDs), solar cells and lasers. Various additives have been widely used in perovskite precursor solutions, aiming to improve the formed perovskite film quality through passivating defects and controlling the crystallinity. The additive’s role of defect passivation has been intensively investigated, while a deep understanding of how additives influence the crystallization process of perovskites is lacking. Here, we reveal a general additive-assisted crystal formation pathway for FAPbI 3 perovskite with vertical orientation, by tracking the chemical interaction in the precursor solution and crystallographic evolution during the film formation process. The resulting understanding motivates us to use a new additive with multi-functional groups, 2-(2-(2-Aminoethoxy)ethoxy)acetic acid, which can facilitate the orientated growth of perovskite and passivate defects, leading to perovskite layer with high crystallinity and low defect density and thereby record-high performance NIR perovskite LEDs (~800 nm emission peak, a peak external quantum efficiency of 22.2% with enhanced stability).

A simple and low-cost technique for the preparation of silicon-oil-infused polydimethylsiloxane (PDMS) coatings with different silicon oil contents have been developed and studied. This material is designed for ice-phobic applications, and thus a high hydrophobic property of PDMS is maintained by avoiding any polar groups such as C═O and OH in the structure. Therefore, the polymer main chain was attached with vinyl and Si-H groups to obtain a cross-linking capability, meanwhile to ensure a nonpolar chemical structure. Its ice-phobic property has been investigated in terms of ice adhesion strength (tensile and shear), water contact angle, icing dynamics using high-speed photography and morphology using TEM, SEM and AFM. The prepared coating surface shows a low surface energy and very low ice adhesion strength of 50 kPa, only about 3% of the value on a bare aluminum (Al) surface. In the silicon oil infused PDMS coatings, the low surface energy of the silicon oil and PDMS, and the high mobility of silicon oil played an important role on the ice-phobic property. Both of these factors offer the surface a large water contact angle and hence a small contact area, leading to the formation of a loose ice layer. In addition, the oil infused polymer structure significantly reduces the contact area of the ice with solid substrate since the ice mostly contacts with the mobile oil. This leads to a very weak interaction between the substrate and ice, consequently significantly reduces the ice adhesion strength on the surface. Therefore, such material could be a good candidate for ice-phobic coatings on which the accumulated ice may be easily removed by a nature force, such as wind, gravity, and vibration.

Muscles and joints make highly coordinated motion, which can be partly mimicked to drive robots or facilitate activities. However, most cases primarily employ actuators enabling simple deformations. Therefore, a mature artificial motor system requires many actuators assembled with jointed structures to accomplish complex motions, posing limitations and challenges to the fabrication, integration, and applicability of the system. Here, a holistic artificial muscle with integrated light-addressable nodes, using one-step laser printing from a bilayer structure of poly(methyl methacrylate) and graphene oxide compounded with gold nanorods (AuNRs), is reported. Utilizing the synergistic effect of the AuNRs with high plasmonic property and wavelength-selectivity as well as graphene with good flexibility and thermal conductivity, the artificial muscle can implement full-function motility without further integration, which is reconfigurable through wavelength-sensitive light activation. A biomimetic robot and artificial hand are demonstrated, showcasing functionalized control, which is desirable for various applications, from soft robotics to human assists.