Synergistic Passivation of Deep and Shallow Defects Enables High‐Efficiency and Stable Low‐Bromine 1.68 eV Bandgap Perovskite Solar Cells

ABSTRACT

The performance and operational stability of wide‐bandgap (WBG) perovskite solar cells (PSCs) are critically limited by voltage loss induced by non‐radiative recombination and halide phase segregation. Deep‐level defects act as dominant recombination centers for voltage loss, while shallow‐level halide vacancies trigger ion migration and halide vacancies trigger ion migration and phase segregation. Herein, we characterize deep‐level and shallow‐level defects via deep‐level transient spectroscopy and photoluminescence measurements, and introduce a high‐dipole zwitterionic additive, pyridinium propyl sulfobetaine (PPS), to simultaneously passivate these defects. PPS strongly coordinates with Pb ²⁺ ions to modulate perovskite crystallization, thereby improving film crystallinity and reducing PbI ₂ residues. Preferentially accumulating at the bottom interface, PPS passivates deep‐level defects through pyridinium and sulfonate functional groups to suppress non‐radiative recombination, while remedying shallow‐level defects to retard ion migration and boost photostability. The resulting reduction in defect density further suggests that these defects are likely enriched at the bottom interface. Enabled by an anti‐solvent‐free process, the 1.68 eV WBG PSC (8% bromine content) delivers an efficiency of 22.29%, (vs. 20.05% for the control) and retains 92.9% of its initial efficiency after 1000 h of maximum power point tracking. This work demonstrates a synergistic defect passivation strategy for high‐performance and stable WBG perovskite.