Situ growth of 2D/3D mixture perovskite interface layer by seed-mediated and solvent-assisted Ostwald ripening for stable and efficient photovoltaics
2D/3D mixed perovskite has been recognized as a very promising method to achieve high efficiency and good ambient stability simultaneously. In this work, we developed a seed-mediated and solvent-assisted Ostwald ripening method to form 2D PEA2PbI4 with gradient mixture in underlying 3D perovskite layer by two step depositions with DMF as additive. By our proposed method the reaction of PEAI with MAPbI3 seed grains preferably produce pure PEA2PbI4 with gradient cladding on 3D perovskite grains rather than traditional 2D/3D planner heterostructure perovskite. We demonstrate this type of perovskite has the better optical performance and stability simultaneously than traditional one. The devices made by our method exhibit an enhancement of 15.5% in average PCE compared with the PSCs with 2D/3D planar heterojunction perovskite. Besides, the PCE of the proposed cell without encapsulation remained above 88% of the original value, which is higher than 83% of the 2D/3D planar heterojunction PSCs after 15 days of storage in an air environment with 35%~55% humidity.