Modulated π‐Bridge of Thioxothiazolidine Derivatives for Passivating Bilateral Interfaces and Grain Boundaries in n‐i‐p Perovskite Solar Cells

Additive engineering has emerged as the predominant approach for enhancing the performance of perovskite solar cells (PSCs). Donor‐π‐acceptor (D‐π‐A) dyes with tailored configurations have proven to be a viable and effective strategy. In this study, we present two asymmetrical D‐π‐A dyes, designated as TZR and TNR. These dyes are designed and synthesized with identical hole‐ and electron‐transporting backbones but feature distinct π‐bridge groups. They are incorporated into the precursor solution of PbI2 to facilitate in‐situ passivation of both interfaces and grain boundaries (GBs) during the formation of the perovskite film. These dyes effectively penetrate both buried and upper interfaces, allowing for the passivation of defects originating from the GBs, and both interfaces. This significantly reduces defects while enhancing charge transport properties. Notably, the π‐bridge composed of benzo[1,2,5]‐ thiadiazole in TZR contains unpaired electrons from nitrogen and sulfur atoms. An impressive power conversion efficiency (PCE) of 25.11% is achieved. This performance significantly surpasses that of TNR‐based and pristine devices, achieving PCEs of 24.47% and 22.88%, respectively. Furthermore, we observed a significant improvement in the stability of the unencapsulated device, attributed to the exceptional hydrophobicity of the D‐π‐A dyes. This study offers valuable insights into achieving high‐performance PSCs through careful molecular design.