In Situ Polymerized Organic Salt Interlayer for Enhanced Performance in Printable Mesoscopic Perovskite Solar Cells

, forming a cross-linked poly(ST) interfacial buffer layer at the junction with the perovskite. This polymer layer enhances interface mechanical strength via electrostatic interactions. Additionally, the flexible polymer side chains help to alleviate interfacial residual stress, while carboxylate groups effectively passivate defects, thereby minimizing non-radiative recombination at the buried interface. The combined effects result in p-MPSCs with improved performance, achieving a power conversion efficiency of 20.33% and demonstrating improved operational stability by retaining >92% of their initial efficiency after 600 h of continuous maximum power point tracking.