A layering technique for achieving pinhole-free organic–inorganic halide perovskite thin films through the vapor–solid reaction

Abstract

Achieving a high-quality organic-inorganic halide perovskite film is essential for highly efficient and stable perovskite solar cells. To enhance the crystalline quality of perovskite thin films, various tactics have been explored to refine the crystal growth process, with a focus on additive engineering and post-treatment methods. Post-treatment, in particular, is recognized as a straightforward and potent approach to significantly improve the crystallinity of perovskite materials. Nevertheless, such post-treatment procedures, whether in solution or vapor phases, often result in an undesirable increase in grain size that leads to pinhole formation. Excessive treatment may result in the generation of larger voids between grains. These defects can lead to substantial charge recombination, impairing the performance of the final device, and this is especially problematic for devices with a large active area. In our research, we introduce an innovative layer-by-layer strategy to overcome the issue of pinholes and boost the overall quality of the film. Our findings suggest that by depositing successive perovskite layers using a vapor–solid reaction, the pinholes in the underlying layer can be effectively filled, resulting in a single, dense, and unified layer. Utilizing this technique, we have fabricated perovskite solar cells that exhibit a notable increase in power conversion efficiency, reaching 21.09%. This layering method presents a viable pathway for the production of large-area, pinhole-free perovskite thin films, which is crucial for advancing the field of perovskite solar cell technology.