Grain Boundary Sealing by Fluorinated Polyamide Acid to Enhance the Low-Pressure Stablility of Perovskite Solar Cells

Under low-pressure conditions, perovskite materials undergo accelerated degradation, initiating from irreversible decomposition at grain boundaries (GBs) and progressing to structural collapse. To address this challenge, we developed an in situ grain boundary sealing strategy using fluorinated polyamide acid (PIF). The PIF polymer undergoes in situ polymerization at GBs, forming an interpenetrating 3D polymer network within perovskite, blocking gas releasing pathways at GBs. The incorporation of PIF enhances the quality of perovskite, and PIF-incorporated perovskite solar cells (PSCs) achieve power conversion efficiencies of 25.28% and 24.42% on rigid and flexible substrates, respectively. PSCs incorporating PIF demonstrate outstanding mechanical stability and robust thermal cycling durability. The PCE degradation rate under 100 mW/cm 2 illumination at 0.02 MPa is reduced by approximately an order of magnitude after PIF incorporation. By further adapting an ITO top electrode and an external encapsulation, the PSCs exhibited a low PCE loss rate of 0.009%/h over 1140 h.