Highly Efficient and Stable Perovskite Solar Cells Using an Effective Chelate-Assisted Defect Passivation Strategy

Perovskite solar cells are sensitive to subtle changes in atmospheric conditions, resulting in problems such as the collapse of the perovskite structure and sharp drops in efficiency. Internal defects are also a big obstacle for high-quality polycrystalline perovskites. At present, it is difficult to control the density of the trapping sites. By using the bidentate chelating agent thenoyltrifluoroacetone (ttfa), the crystallization kinetics, grain sizes, and crystal defect of Cs-, methylammonium-, and formamidinium-based perovskite materials can be to effectively controlled through a nucleation and growth process for the preparation of perovskite crystals. Crystalline-state tuning during the crystallization process to obtain better quality perovskite thin films can be achieved with no additional operation, which is suitable for the needs of modern industrial production and management. The chelating agent can effectively passivate the defects in perovskite films, leading to a low defect density and a long charge carrier lifetime. As a result, the ttfa-passivated perovskite solar cell demonstrated a high power conversion efficiency of 19.70 % with superior stability retention of 64 % of the initial power conversion efficiency after two weeks unencapsulated storage in an adverse atmosphere with approximately 50 % relative humidity.