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

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.