High-performance and moisture-stable perovskite solar cells with a 2D modified layer via introducing a high dipole moment cation

Abstract

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 a 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 an effective passivation effect, leading to reduced interface defect sites and suppressed nonradiative recombination. Moreover, the remarkable hydrophobicity of the 2D modified layer can provide 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 showed a high power conversion efficiency (PCE) of 19.24%, with an open-circuit voltage (V_oc) of 1.08 V, a short circuit current density (J_sc) of 22.65 mA cm⁻² and a fill factor (FF) of 78%. After aging under a relative humidity of 50 ± 5% for 60 days, the modified PSCs retain 88% of their initial PCE. Our work provides a valuable strategy to prepare a 2D perovskite modified layer with a high dipole moment cation for high-performance PSCs with superior moisture stability.