π‐Conjugation and Hole–Electron Separation in Self‐Assembled Monolayers Enables Efficient Inverted Perovskite Solar Cells

ABSTRACT Self‐assembled monolayers (SAMs) have emerged as the material of choice for hole transport layers (HTLs) in inverted perovskite solar cells (PSCs), where their favourable interfacial contact with the perovskite active layer enables remarkable power conversion efficiency (PCE). However, commercially available carbazole‐phosphonic acid‐based SAMs with excessively long alkyl chain linkers exhibit compromised hole transport due to their insulating properties. Here, through a stepwise chemical modification of conjugated linkers and anchor groups, we investigate a series of SAMs with enhanced hole–electron delocalization of molecules. Among the molecules, MCz‐ICA featuring a unique conjugation‐extension structure comprising a phenyl ring and two vinylene units as the linker, along with a cyanoacetic acid anchor, exhibits a more favourable configuration. The enhanced orbital delocalization and hole–electron separation increase the molecular dipole moment, thereby improving the interfacial contact of both perovskite and NiO _x layers, which facilitates efficient hole extraction and suppresses non‐radiative recombination, and ultimately leads to an impressive PCE of 26.69% (certified 26.47%) of the p‐i‐n structured PSCs. Moreover, the device could maintain over 92.5% of its initial performance after 1000 h of continuous operation according to the ISOS‐L‐2I protocol.