Dual‐Interface Engineered 2D/3D/2D Heterojunctions for Stable Inverted FACsPbI ₃ Perovskite Solar Cells

Defects at surfaces and grain boundaries of perovskite films are major sources of nonradiative recombination and inefficient charge transport, limiting the power conversion efficiency (PCE) and stability of inverted perovskite solar cells (IPSCs). Methylammonium (MA)‐free perovskites (e.g., Cs 0.05 FA 0.95 PbI 3 ) offer improved thermal stability but face challenges, including poor crystallinity and high defect density due to uncontrolled crystallization kinetics. In this work, we have developed a dual‐interface passivation strategy to address these issues. Guided by density functional theory (DFT) calculations, 2‐aminoindene‐2‐carboxylate hydrochloride (2‐AI‐2‐CMEH) was incorporated into the perovskite precursor solution to regulate the crystallization process and form a 2D/3D heterostructure at the buried interface, enhancing hole‐transport layer contact and bulk defect passivation. Subsequently, 2‐thienylethylammonium chloride (TEACl) was applied to construct a 3D/2D heterojunction at the top interface, optimizing the energy level alignment and improving the electron extraction by reducing trap‐state density. The optimized IPSCs achieved an improved PCE of 23.57%, a significant increase from the control device (19.26%), with an open‐circuit voltage ( V OC ) of 1.116 V and a fill factor (FF) of 82.89%. This dual‐interface engineering approach effectively suppresses nonradiative recombination and enhances charge transport, providing a pathway for the high‐efficiency and stable MA‐free perovskite photovoltaics.