Microstructures and Grain Boundaries of Halide Perovskite Thin Films

Halide perovskite (HP) thin films used in various applications are ubiquitously polycrystalline and have a microstructure comprising grains and grain boundaries (GBs) where those grains meet. The microstructures of HP thin films have been found to have profound effects on the properties, performance, and stability of the resulting devices. Therefore, it is very important to study HP thin-film microstructures and their evolution based on sound materials science principles for making meaningful scientific and technological progress in HP thin films and resulting devices. Here, we first discuss the characteristics of microstructures in HP thin films, followed by the genesis and evolution of those microstructures. Next, examples of microstructural effects on the stability and performance of HP thin films and devices are presented and analyzed critically. Finally, an outlook is introduced on future research directions involving HP thin-film microstructures and GBs that will enable perovskite solar cells, and other HP-based devices reach their full potential.