Defects locating within grain boundaries or on the film surface, especially organic cation vacancies and iodine vacancies, make the fabrication of perovskite solar cells (PSCs) with superior performance a challenge. Organic ammonium iodide is a promising candidate and has been frequently used to passivate these defects by forming two-dimensional (2D) perovskite. In this work, it is found that the chain length of organic ammonium iodide is a crucial factor on the defect passivation effect. Compared to butylammonium iodide, the hexylammonium iodide (HAI)-derived 2D perovskite is more efficient in decreasing interfacial defects, resulting in a notably enhanced photoluminescence lifetime and a more suppressed interfacial charge recombination process. As a consequence, the ultimate power conversion efficiency (PCE) has reached 20.62% (3D + HAI) as compared to 18.83% (3D). Moreover, the long-term durability of the corresponding PSCs against humidity and heat is simultaneously improved. This work once again demonstrates that the 2D/3D structure is promising for further improving the PCE and stability of PSCs.
Keywords: 2D/3D stacking structure; interfacial passivation; organic ammonium iodide; perovskite solar cell; stability.