Synergistic Crystallization and Passivation by a Single Molecular Additive for High‐Performance Perovskite Solar Cells

Abstract With its power conversion efficiency surpassing those of all other thin‐film solar cells only a few years after its invention, the perovskite solar cell has become a superstar. Controlling the intermediate phase of crystallization is a key to obtaining high‐quality perovskite films. Herein, a single molecule additive, N,N‐dimethylimidodicarbonimidic diamide hydroiodide (DIAI), is incorporated into the perovskite precursor to eliminate the influence of intermediate phases. By taking advantage of the interaction of DIAI and dimethyl sulfoxide (DMSO), the intermediate phase FAI‐PbI₂‐DMSO complex is eliminated, and δ‐FAPbI₃ is entirely converted to the desired α‐FAPbI₃ during the crystallization step, resulting in enlarged grain size and improved crystalline quality. This is the first observation in the solution method that FAPbI₃ can be obtained without an intermediate phase for high‐performance perovskite solar cells. Furthermore, DIAI is effective at passivating surface defects, resulting in reduced defect density, increased carrier lifetime, and improved device efficiency and stability. The champion device achieves an efficiency of 24.13%. Furthermore, the bare device without any encapsulation maintains 94.1% of its initial efficiency after ambient exposure over 1000h. This work contributes a strategy of synergistic crystallization and passivation to directly form α‐FAPbI₃ from the precursor solution without the influence of intermediate impurities for high‐performance perovskite applications.