Stability of hole-selective self-assembled monolayers in inverted perovskite solar cells

Inverted p-i-n perovskite solar cells (PSCs) based on self-assembled monolayers (SAMs) as hole-selective layers (HSLs) have produced potential record efficiencies of more than 26% by tuning work function, dipole, and passivation defects. However, the stability of the SAM molecules, the stability of the molecular anchoring conformation, and the impact on the stability of subsequent PSCs have not been clearly elucidated. In this review, we systematically discussed the intrinsic connection between the molecular conformation (including anchoring groups, spacer groups, and terminal groups) and the stability of SAMs. Sequentially, the research progress of SAMs as HSLs in improving the stability of PSCs is summarized, including photostability, thermal stability, ion migration, and residual stress. Finally, we look forward to the shortcomings and possible challenges of using SAMs as HSLs for inverted PSCs.