This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). Non-Technical Description: Halide perovskites semiconductors have recently attracted considerable attention for devices such as solar cells and light-emitting diodes. However, their poor stability results in devices with short lifetimes, precluding widespread use. One particular challenge is that movement of ions alters the electronic properties of perovskites. Thus, understanding ion transport is essential to solve the stability problem. The PI will develop novel structures from two-dimensional perovskites and quantify how ions diffuse and migrate under heat, light, and electrical bias. Understanding these fundamental questions will help researchers design perovskites with enhanced stability. This project also provides interdisciplinary training to undergraduate and graduate students. They will gain critical-thinking and problem-solving skills needed for careers in materials science, chemical and electrical engineering, and semiconductor technology. Technical Description: Accurately quantifying ion transport in halide perovskites is challenging. The current understanding is based primarily on conventional charge transport studies, where the contribution from electrons and co-movement of cations and anions is difficult to separate. Furthermore, ionic diffusion studies have been limited to polycrystalline thin films where grain boundaries and defects play critical rol