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/SnO2/perovskite/spiro-OMeTAD/Ag via a combination of R2R microgravure printing and slot-die coating under ambient conditions with a relative humidity of approximate to 40%. A mixture of isopropanol and water is used to dilute an as-purchased SnO2 colloid solution and modify the contact between the electron-transport layer (ETL) and substrate, leading to a smooth morphology of the R2R-printed ETL SnO2 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 SnO2 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.