Natural Product Additive with Multifunctional Groups Enhancing the Efficiency and Stability of Perovskite Solar Cells

Perovskite solar cells (PSCs) are widely studied as the most promising photovoltaic technology, but their performance is sensitive to the morphology and the defect density of the perovskite films. Herein, additive engineering strategy is applied to further improve the film morphology and device performance by doping a small amount of natural product, D‐Aspartic acid (D‐2‐Aminobutanedioic acid, D‐Asp), into perovskite precursor solution. The modified device exhibits a greatly enhanced power conversion efficiency of 22.7%, which is unprecedented for PSCs doped with natural amino acids, and 3000 h stability in ambient air is achieved. Through systematical characterizations, it is concluded that D‐Asp could result in thicker film formation, outstanding perovskite film morphology, and reduced defect sites passivated by the multiple functional groups. The results prove that the performance and stability of the state‐of‐the‐art mixed ion PSCs with regular architecture could be effectively enhanced by D‐Asp. The minimum usage of the natural product as an additive is beneficial for the fabrication process and cost‐control in the industrialization of PSCs. This work also highlights the different passivating mechanisms for the molecules with multiple functional groups which are meaningful for materials design.