In Situ Investigations of Al/Perovskite Interfacial Structures.

Interfacial properties of perovskite layers and metal electrodes play a crucial role in device performance and long-term stability of perovskite solar cells. In this work, we performed a comprehensive study of the interfacial structures and ion migration at the interface of a CHNHPbI perovskite layer and an Al electrode using in situ synchrotron radiation photoemission spectroscopy measurements. It was found that the Al electrode can react with the perovskite layers, leading to the formation of aluminum iodide species and the bonding between Al and N, as well as the reduction of Pb ions to metallic Pb species at the interface.

Formic acid adsorption and decomposition on clean and atomic oxygen pre-covered Cu(100) surfaces.

Formic acid adsorption and decomposition on clean Cu(100) and two atomic oxygen pre-covered Cu(100) surfaces have been studied using surface science techniques including scanning tunneling microscopy, low-energy electron diffraction, x-ray photoelectron spectroscopy, and infrared reflection-absorption spectroscopy. The two atomic oxygen pre-covered Cu(100) surfaces include an O-(22 ×2)R45° Cu(100) surface and an oxygen modified Cu(100) surface with a local O-c(2 × 2) structure. The results show that the O-(22 ×2)R45° Cu(100) surface is inert to the formic acid adsorption at 300 K.

Supramolecular Tessellations at Surfaces by Vertex Design.

Assembly and tessellation of organic species at surfaces are important for the design of advanced materials, particularly for the development of spontaneous self-assemblies of supramolecular systems of increasing complexity. However, there are few examples where the ability to steer the system between supramolecular tessellations has been achieved. Here, we demonstrate a series of steps to reduce and then restore molecular symmetry; those variations impact vertex symmetry and thus generate a series of tessellations that reflect the molecular symmetry.