Flexible Planar Heterojunction Perovskite Solar Cells Fabricated via Sequential Roll‐to‐Roll Microgravure Printing and Slot‐Die Coating Deposition

It is highly desirable to develop large‐scale, low‐cost fabrication processes for flexible perovskite solar cells ( f ‐PSCs) under ambient conditions for accelerating their potential commercialization. Roll‐to‐roll (R2R) printing technology enables high‐output manufacturing and is well suited for commercially processing f ‐PSCs. Herein, triple‐cation f ‐PSCs are developed with a planar heterojunction structure consisting of polyethylene‐2,6‐naphthalate/indium tin oxide/SnO 2 /perovskite/spiro‐OMeTAD/Ag via a combination of R2R microgravure printing and slot‐die coating under ambient conditions with a relative humidity of ≈40%. A mixture of isopropanol and water is used to dilute an as‐purchased SnO 2 colloid solution and modify the contact between the electron‐transport layer (ETL) and substrate, leading to a smooth morphology of the R2R‐printed ETL SnO 2 layer. Furthermore, suitable intrinsic organic salt additives and the N 2 gas blowing‐assisted process are introduced to effectively improve the crystallization of the perovskite, resulting in a high‐quality perovskite film via R2R. After the optimization, the f ‐PSCs based on the R2R‐printed ETL SnO 2 and the perovskite film under an ambient condition show a power conversion efficiency (PCE) of up to 10.56% and an average PCE of 9.97%. This study provides a potential strategy for commercially fabricating f ‐PSCs via a scalable and efficient R2R printing process.