Strong Coupling of NiOx and Self‐Assembled Molecules via Inserted Reductant for High‐Performance Inverted Perovskite Solar Cells

Abstract Self‐assembled molecules (SAMs) deposited on nickel oxide (NiO _x ) are the basis for achieving high‐performance inverted perovskite solar cells (PSCs). Unfortunately, the dissolution and redeposition of SAMs caused by the perovskite precursors leads to leaky monolayers, resulting in perovskite degradation and reduced stability. Here, a novel method is reported to realize strong coupling between NiO _x and SAMs via inserted reductant [9tris(2‐carboxyethyl)phosphine hydrochloride (TCEP)] for an integrated NiO _x ‐SAMs hole transport layer (HTL). TCEP reduces NiO _x and in situ forms C═O···Ni coordinated bond and O─H···O─Ni hydrogen bond, while its ‐COOH is connected with SAM's ‐PO(OH) ₂ by phosphonate and hydrogen bond, which improve the compactness of SAMs, thereby strengthening hole extraction and lowering interfacial non‐radiative recombination. Simulation calculations demonstrate that the HTL strongly coupled by TCEP has a stronger adsorption energy, significantly improving device long‐term stability. Therefore, the device based on integrated NiO _x ‐SAMs HTL obtains a substantial efficiency of 26.34%. The devices maintain an impressive 97.5% of their original efficiency after 1000 h of operation under 1‐sun illumination and 90.1% after 1000 h of thermal treatment at 85 °C in nitrogen atmosphere. This work offers new horizons for designing NiO _x ‐based HTLs with high SAMs coverage for high‐performance PSCs.