Constructing All‐Inorganic Perovskite/Fluoride Nanocomposites for Efficient and Ultra‐Stable Perovskite Solar Cells

Abstract Organic‐inorganic hybrid perovskite solar cells (PSCs) have rapidly developed over the past decade and have achieved the latest certified power conversion efficiency (PCE) up to 25.5%. However, unsatisfactory long‐term operational stability for these hybrid PSCs remains a huge obstacle to further development and commercialization. Herein, a unique hetero‐structured CsPbI₃/CaF₂ perovskite/fluoride nanocomposites (PFNCs) is fabricated via a newly developed facile two‐step hetero‐epitaxial growth strategy to deliver efficient and ultra‐stable PSCs. After being incorporated into the crystal lattice of α‐phase CsPbI₃ perovskite, the cubic‐phase CaF₂ in the resultant CsPbI₃/CaF₂ PFNCs can not only passivate the intrinsic defects of CsPbI₃ perovskite itself but also effectively suppress the notorious ion migration in hybrid perovskite Cs_0.05FA_0.81MA_0.14PbI_2.55Br_0.45 (CsFAMA) thin‐films of PSCs. As such, the CsFAMA PSC devices based on CsPbI₃/CaF₂‐deposited perovskite thin‐film achieve a mean PCE of 20.45%, in sharp contrast to 19.33% of the control devices without deposition. Specifically, the CsPbI₃/CaF₂‐deposited PSC retains 85% of its original PCE after 1000 h continuous operation at the maximum power point under AM 1.5G solar light, far better than those of the control and CsPbI₃‐deposited PSCs with a device T₈₅ lifetime of 315 and 125 h, respectively.