An organic cationic salt, hexamethylenediamine diiodide (HDADI), is introduced into formamidinium tin iodide (FASnI 3 ) perovskite solar cells (PSCs) by consideration of amino group passivation of HDA 2+ to iodide of SnI 6 4− and assisted links of amino groups at both ends of HDA 2+ to the perovskite unit cell to form the Dion−Jacobson (DJ) layered two-dimensional (2D) perovskite. X-ray diffraction and grazing-incidence wide-angle Xray scattering characteristics exclude the formation of the DJ layered 2D perovskite. A decent power conversion efficiency (PCE) and stability are derived from the high-quality perovskite films with large coverage, high crystallinity, and disappeared pinholes as well as increased radiative recombination and a prolonged carrier lifetime, which are associated with the interaction of NH 3 + and SnI 6 4− octahedra via a hydrogen bond. The interaction not only neutralizes charged defects or dangling bonds of perovskites but also forms a shield to retard the oxidation of Sn 2+ to Sn 4+ and reduce Sn vacancies. Applications of the HDADI-treated FASnI 3 films into PSCs acquire a champion PCE of 7.6% and an outstanding long-term stability of over 550 h to retain 80% of the initial efficiency in a glovebox with a N 2 environment. This work may guide the design of highly stable and efficient Sn-based PSCs.

Additives with multiple functional groups are introduced to passivate defects in the perovskite film, yielding efficient and stable perovskite solar cells.

Manipulating perovskite crystallization to prepare high‐quality perovskite films is the key to achieving highly efficient and stable perovskite solar cells (PSCs). Here, a dynamic strategy is proposed to modulate perovskite crystallization using a resonance hole‐transporting material (HTM) capable of fast self‐adaptive tautomerization between multiple electronic states with neutral and charged resonance forms for mediating perovskite crystal growth and defect passivation in situ. This approach, based on resonance variation with self‐adaptive molecular interactions between the HTM and the perovskite, produces high‐quality perovskite films with smooth surface, oriented crystallization, and low charge recombination, leading to high‐performance inverted PSCs with power conversion efficiencies approaching 22% for small‐area devices (0.09 cm2) and up to 19.5% for large‐area devices (1.02 cm2). Also, remarkably high stability of the PSCs is observed, retaining over 90%, 88%, or 83% of the initial efficiencies in air with relative humidity of 40–50%, under continuous one‐sun illumination, or at 75 °C annealing for 1000 h without encapsulation.