Molecular Engineering of Multi-Site Small-Molecule Chelation for Highly Efficient and Stable n-i-p Perovskite Solar Cells.

Abstract

Li-TFSI-doped Spiro-OMeTAD is the benchmark hole-transporting material for high-performance n-i-p perovskite solar cells (PSCs). Yet its intrinsic instability, arising from Li+ migration, has long been regarded as an inevitable trade-off for achieving high efficiency. Despite extensive efforts, no alternative dopant system has yet fully matched the Li-TFSI/t-BP system in simultaneously achieving high doping efficiency and well-established processability. Instead, these alternatives often sacrifice efficiency for improved stability, or they are hampered by synthetic complexity that precludes large-scale application. Here we design a multifunctional small-molecule chelator, TPABT3, with multiple coordination sites to immobilize Li+ ions and stabilize doped Spiro-OMeTAD. This molecule concurrently suppresses ion migration, induces ordered molecular packing, and enhances p-type doping efficiency, while optimizing energy-level alignment at the perovskite/HTL interface. The resulting two-step-fabricated FAPbI3 devices deliver an outstanding power conversion efficiency of 26.03% with negligible hysteresis. Moreover, the PSCs retain over 90% of their initial efficiency after 1000 h under ISOS-L-1 aging conditions. This work establishes multi-site molecular chelation as an effective, generalizable strategy for achieving highly efficient and stable n-i-p perovskite photovoltaics.

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