Construction and mechanistic understanding of high-performance all-air-processed perovskite solar cells: Via mixed-cation engineering

All-air-processed perovskite solar cells (PSCs) have attracted increasing attention due to their low cost and simplified manufacturing processes. At present, there is a need to fabricate efficient and stable PSCs in the air. In this work, dense perovskite films with a large grain size and low trap-state density can be obtained, when 30% of formamidinium (FA+) is incorporated into methylammonium lead iodide (MAPbI3). The champion device with a planar architecture of FTO/SnO2/FA0.3MA0.7PbI3/Spiro-OMeTAD/Au achieves a maximum power conversion efficiency (PCE) of 19.50%, which is one of the highest efficiencies yet reported for all-air-processed PSCs. In addition, the unencapsulated device exhibits excellent long-term stability and remarkable thermal stability, retaining over 85% of its original PCE after storage in ambient atmosphere for 90 days (>2100 h) and over 84% efficiency after storage at 100 °C for 27 h without inert conditions. Furthermore, the mechanisms underlying the improved performance are revealed through powerful characterization techniques and density functional theory calculations. Our work provides a facile strategy for the development of a new generation of fully air-processed PSCs for commercialization.