Fully Screen‐Printed Perovskite Solar Cells with 17% Efficiency via Tailoring Confined Perovskite Crystallization within Mesoporous Layer

Abstract Using a screen‐printing techniques is thought to be a good candidate for simplified, cost‐effective, reliable, and scalable fabrication of fully printed perovskite solar cells (PSCs) for industrialization. Nevertheless, the screen‐printing of perovskite film has not been realized until recently. This group finished the work using ionic liquid methylamine acetate (MAAc) as pure solvent. However, the space‐confining effect during the perovskite crystallization in mesoporous impeded the escape of bottom MAAc molecules, which leads to the poor crystalline quality of the screen‐printed film. In this work, ionic liquid methylamine propionate (MAPa) with stronger coordination is introduced as a co‐solvent to promote the escape of MAAc molecules by forming the solvent volatilization channels in a confined mesoporous structure, which results in the complete MAAc volatilization and high filling degree of perovskite crystals inside the mesoporous structure. Also, MAPa promotes the vertical growth of perovskite crystals and coordinates with unbonded Pb 2+ on the perovskite surface, leading to efficient charge transport and interfacial band alignment of the screen‐printed film. Finally, fully screen‐printed PSCs yields a champion power conversion efficiency (PCE) of ≈17%, which is the record value for fully screen‐printed PSCs. Moreover, the unencapsulated device shows robust operational stability that maintains >85.3% of initial PCE (25%RH and 25 °C) under continuous illumination at the maximum power point after 250 h.