CAREER: Understanding and Quantifying Ion Migration and Diffusion in Two-Dimensional Halide Perovskite Heterostructures

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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 roles. In this project, novel epitaxially grown 2D perovskite heterostructures, a microscopically well-defined diffusion couple, will be fabricated and used as a platform to probe ionic migration and diffusion. This project will establish a comprehensive family of lateral and vertical 2D halide perovskite heterostructures; quantify ionic diffusion and migration under different external stimuli; elucidate the ionic diffusion and migration mechanism; identify the most promising materials stabilization strategies; and finally demonstrate proof-of-concept devices with enhanced stability. The education objective of the project is to build an interdisciplinary materials science program at Purdue University that transcends traditional boundaries between science and engineering disciplines to educate our next-generation scientists and engineers. Specifically, new curriculum and new teaching methods that cut-across traditional boundaries for undergraduate and graduate education will be developed. Raising public awareness of materials science and semiconductors is another important objective of this project. Finally, an impactful global network of science and education through partnership with developing countries (e.g., Colombia and Indonesia) will be built.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.