Suppressing Halide Segregation via Pyridine‐Derivative Isomers Enables Efficient 1.68 eV Bandgap Perovskite Solar Cells

Abstract Light‐induced phase segregation is one of the main issues restricting the efficiency and stability of wide‐bandgap perovskite solar cells (WBG PSCs). Small organic molecules with abundant functional groups can passivate various defects, and therefore suppress the ionic migration channels for phase segregation. Herein, a series of pyridine‐derivative isomers containing amino and carboxyl are applied to modify the perovskite surface. The amino, carboxyl, and N‐terminal of pyridine in all of these molecules can interact with undercoordinated Pb²⁺ through coordination bonds and suppress halide ions migration via hydrogen bonding. Among them, the 5‐amino‐3‐pyridine carboxyl acid (APA‐3) treated devices win the champion performance, enabling an efficiency of 22.35% (certified 22.17%) using the 1.68 eV perovskite, which represents one of the highest values for WBG‐PSCs. This is believed to be due to the more symmetric spatial distribution of the three functional groups of APA‐3, which provides a better passivation effect independent of the molecular arrangement orientation. Therefore, the APA‐3 passivated perovskite shows the slightest halide segregation, the lowest defect density, and the least nonradiative recombination. Moreover, the APA‐3 passivated device retains 90% of the initial efficiency after 985 h of operation at the maximum power point, representing the robust durability of WBG‐PSCs under working conditions.