Robust Fully Screen‐Printed Perovskite Solar Cells Based on Synergistic Ostwald Ripening

Fully screen-printed process for low-cost manufacturing significantly enhances the commercial competitiveness of perovskite solar cells (PSCs). However, the controllable crystallization in screen-printed perovskite thin films using high-viscosity ionic liquids has been suggested to be difficult, which hampers further development of fully screen-printed perovskite devices in terms of application expansion and performance improvement. Here, we report a synergistic ripening strategy to fully control crystallization by employing methylamine propionate (MAPa) ionic liquid and water (H₂O, moisture in the air). We found that a reversible and sustainable ripening process was activated by integrating MAPa/H₂O in both externally and internally into perovskite crystals. MAPa effectively prevents the loss of organic salts and maintains the dispersion of Pb-I framework, preventing the perovskite component loss and decomposition. H₂O and organic salts trends to form hydration complexes, which lowers the energy barrier and enhances the reactivity of the humidity-induced Ostwald ripening reaction. These improvements allow the screen-printed perovskite thin films achieve controlled secondary growth and ion exchange, thereby reducing defects and optimizing energy level alignment. The resulting fully screen-printed PSCs exhibits a record power conversion efficiency of 19.47 % and an operational stability over 1,000 h with maintaining 91.6 % of the highest efficiency under continuous light stress at maximum power point.