High-performance and moisture-stable perovskite solar cells with a 2D modified layer via introducing high dipole moment cation
Recently, perovskite solar cells (PSCs) have represented a significant breakthrough due to their excellent photoelectric properties. However, short lifetime and poor moisture stability make it difficult for PSCs to achieve further application. Here, we have introduced a fluorinated ammonium salt (2, 2, 2-triﬂuoroethylamine hydroiodide, FEAI) with high dipole moment to grow a 2D modified layer ((FEA)2PbI4) at the interface of perovskite/HTL. Due to the electronegativity of FEA+, the 2D modified layer brings about effective passivation effect, leading to reduced interface defect site and suppressed nonradiative recombination. Moreover, the remarkable hydrophobicity of 2D modified layer can provide a protection of 3D perovskite from moisture erosion but not at the expense of efficiency. As a result, based on (FAPbI3)0.85(MAPbBr3)0.15, the FEAI-modified PSCs obtained high power conversion efficiency (PCE) of 19.24%, with an open-circuit voltage (Voc) of 1.08 V, a short circuit current density (Jsc) of 22.65 mA cm-2 and a fill factor (FF) of 78%. After aging under the relative humidity of 50± 5% for 60 days, the modified PSCs retain 88% initial PCE. Our work provides a valuable strategy to prepare a 2D perovskite modified layer with high dipole moment cation for high-performance PSCs with superior moisture stability.