Defect‐Passivating and Dense Indolocarbazole‐Based Self‐Assembled Monolayers for Efficient Inverted Perovskite Solar Cells With over 26.1% Efficiency

ABSTRACT Self‐assembled monolayers (SAMs) are widely used in NiO _x ‐based inverted perovskite solar cells (PSCs). However, the poor wettability, low surface coverage, inhomogeneous distribution, and inadequate defect passivation capability of SAMs limit further improvements in the efficiency and stability of IPSCs. Herein, we have developed a series of indolocarbazole‐based SAMs, namely, D3PAICz‐1, M3PAICz‐1, D3PAICz‐2, and M3PAICz‐2. We systematically investigated how the nitrogen positions in indolocarbazole‐based SAMs and the anchoring group number synergistically influence device performance and stability. Among these SAMs, monophosphonate‐anchored M3PAICz‐1 demonstrates advantages in surface wettability, compactness, film uniformity, energy level alignment, hole extraction, and defect passivation. Consequently, the corresponding 1.55 eV bandgap PSCs achieved the highest power conversion efficiency (PCE) of 26.12% and excellent air stability. More interestingly, M3PAICz‐1 also endowed 1.68 eV wide‐bandgap (WBG) PSCs with an impressive efficiency of 22.19%, demonstrating its good universality as HTL. Our findings provide valuable insights for designing novel SAM molecules targeted at practical high‐performance PSCs.