Hexylammonium Iodide Derived Two-Dimensional Perovskite as Interfacial Passivation Layer in Efficient Two-Dimensional/Three-Dimensional Perovskite Solar Cells.

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.