Fluorinated Pyrimidine Bridged Buried Interface for Stable and Efficient Wide‐Bandgap Perovskite Solar Cells

Abstract The buried interface of wide‐bandgap (WBG) perovskite solar cells (PSCs) is crucial for effective charge transfer and device stability. In this study, 2,4‐diamino‐6‐fluoropyrimidine (DMFP) is incorporated into the perovskite layer to form a molecular bridge at the buried interface between the perovskite and MeO‐4PACZ. DMFP treatment reduces the agglomeration of MeO‐4PACZ, resulting in denser and more uniform self‐assembled monolayers (SAMs) by inducing favorable crystal orientation. In addition, the strong chemical interaction between DMFP and perovskite films significantly reduces defect state density and promotes the growth of high‐quality perovskite grains. Moreover, DMFP treatment effectively modulates the energy levels of perovskites, facilitating interfacial charge extraction. As a result, WBG PSCs treated with DMFP demonstrate a remarkable power conversion efficiency (PCE) of 21.96%, with an enhanced short‐circuit current density (J SC ) of 21.60 mA cm −2 and a high open‐circuit voltage (V OC ) of 1.23 V. The prepared WBG PSCs retain 95.5% of their initial efficiency after 1500 h of aging at a relative humidity of ≈30% in air, indicating excellent humidity stability. This study contributes to a deeper understanding of the perovskite buried interface and proposes a collaborative approach for developing high‐performance WBG PSCs.