Multifunctional Molecule Modification toward Efficient Carbon‐Based All‐Inorganic CsPbIBr2 Perovskite Solar Cells

Abstract Favorable stability is a big challenge for the commercialization of perovskite solar cells, and all‐inorganic perovskite semiconductors have attracted much attention due to their excellent performance in this field. In reality, the poor stability is mainly due to the high‐density defects in the perovskite films, which provide a channel for charge nonradiative recombination and ion migration. In this work, a multifunctional aminoguanidine hemisulfate (AG HSUL) is introduced into the CsPbIBr 2 perovskite layer to achieve defect passivation. Guanidine cations (GA + ) can form strong hydrogen bonds with under‐coordinated halogen ions to stabilize the crystal lattice; the nitrogen atom in the amino group can form a complex with the under‐coordinated lead ion; inorganic acids and ions can not only compensate for halogen anion vacancies, but also combine with lead clusters or capped lead ions to reduce defect density. The synergistic effect of anions and cations can effectively passivate the defects, and an energy conversion efficiency of 10.10% is obtained at the optimal concentration of modification. In addition, carbon electrodes are used instead of metal electrodes, which greatly reduces the cost. The results provide a new idea for the development of efficient all‐inorganic CsPbIBr 2 perovskite solar cells.