Regulating Electron-Density Distribution of Pyridine Derivative Passivators for Efficient Carbon-Based CsPbI_3-xBr_x...

CsPbI_3-xBr_x carbon-based all-inorganic perovskite solar cells (C-IPSCs) are promising due to their thermal stability, low cost, and suitable bandgap for tandem applications, yet their performance is limited by energy losses caused by charged defects at the perovskite surface. Herein, we report a molecular engineering strategy to enhance defect passivation by regulating the electron-density distribution of pyridine derivatives. In 4-amino-6-chloropicolinic acid (ACA), the electron-donating -NH₂ group enriches electron density at the passivation sites (pyridinic N and carboxyl O), strengthening coordination with undercoordinated Pb²⁺. The -NH₂ group of ACA interacts with I^- in the perovskite lattice via hydrogen bonding, suppressing ion migration and stabilizing the crystal lattice. Furthermore, ACA adsorption improves energy-level alignment at the interface, facilitating charge extraction. As a result, ACA-treated C-IPSCs achieve a champion power conversion efficiency of 15.84% with an open-circuit voltage of 1.19 V, significantly outperforming the control devices (13.11%, 1.10 V), with enhanced operational stability.