Molecular confinement for enhanced interfacial contact and performance in inverted perovskite solar cells

Self-assembled molecule (SAM) layers have significantly enhanced the efficiency of inverted perovskite solar cells (PSCs). However, SAM aggregation leads to non-uniform interfacial contact, limiting further improvements in efficiency and stability. Here we employ perfluoro-2-propoxypropanoic acid (PFA) to construct a molecular confinement structure on the surface of the NiOx substrate. This confinement structure enables uniform embedding of SAMs within the PFA sub-monolayer and prevents their vertical stacking. Together, PFA and SAM form a complete interlayer that enhances the interface contact and reduces defects between NiOx and perovskite. Moreover, PFA molecules in the confinement structure interact with the buried perovskite interface via hydrogen bonding and dipolar interaction, further stabilizing the structure. These enhancements enable PSCs to achieve an efficiency of 26.84% (certified value of 26.79%) with a high fill factor of 86.61%. And the device exhibits excellent operational stability, retaining 94.6% of its initial efficiency after 800 hours of 1-sun maximum power point tracking under the ISOS-L-1 protocol. Yang et al. report a molecular confinement strategy that regulates self-assembled monolayer packing and stabilizes buried interfaces in inverted perovskite solar cells, enabling a power conversion efficiency of 26.84% with an 86.6% fill factor.