Super ‐Hydrophilic SAMs via Chlorine Substituted All‐Hydrophilic Molecule Modification for Monolithic Perovskite‐Silicon Tandem Solar Cells

Abstract Self‐assembled monolayers (SAMs) have emerged as highly promising hole transport layers for inverted perovskite solar cells, owing to their low parasitic absorption and effective charge extraction. However, their inherent strong hydrophobicity often inhibits the quality and uniformity of perovskite films and induces defects at the buried interface. In this study, a chlorine‐substituted all‐hydrophilic molecule is introduced to modify the buried interface. Such decoration transforms the hydrophobic SAM into a super‐hydrophilic surface, significantly enhancing the quality and uniformity of perovskite films. This chlorine‐substituted molecule exhibits a strong coordination with lead ions and effectively passivates defects at the buried interface of perovskite films. As a result, the single‐junction wide‐bandgap (1.67 eV) perovskite solar cell achieves a power conversion efficiency of 23.97%, the highest value achieved for MeO‐2PACz‐based devices. Furthermore, the perovskite‐silicon tandem solar cell reaches an efficiency of 31.12%. Additionally, the applicability of chlorine‐functionalized all‐hydrophilic molecule at the buried interface modification is demonstrated to various SAMs (4PADCB, 2PACz and Me‐4PACz) and narrower‐ or wider‐bandgap (1.61, 1.68, and 1.72 eV) perovskite solar cells. This work presents a promising strategy to overcome the challenges associated with SAM‐based perovskite solar cells, paving the way for further performance advancement.