Molecular Engineering of Spiro‐OMeTAD for Durable and Efficient Perovskite Photovoltaics

In n‐i‐p structured perovskite solar cells, π‐conjugated small‐molecule spiro‐methoxydiarylamine (spiro‐OMeTAD) serves as the state‐of‐the‐art hole‐transporting material, whose performance relies heavily on doping with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 4‐tert‐butylpyridine (tBP). Nevertheless, the facile migration of Li + cations and the severe thermal volatilization of tBP under operational conditions inevitably degrade device longevity. To circumvent these bottlenecks, perfluorobutanesulfonamide (PFBSA) is introduced into spiro‐OMeTAD as a multifunctional additive, which enables simultaneous interactions with Li + and tBP. The Lewis‐basic sulfonyl oxygen moieties of PFBSA coordinate with Lewis‐acidic Li + to suppress ion migration; meanwhile, the amino groups of PFBSA form robust hydrogen bonds with the pyridyl moiety of tBP, restraining its thermal escape at elevated temperatures. Moreover, PFBSA facilitates the dissociation of TFSI − anions, accelerates the oxidation of spiro‐OMeTAD, and elevates film hole mobility. The liberated TFSI − further triggers the generation of spiro‐OMeTAD ·+ , realizing efficient p‐type doping. Benefiting from the multifunctional regulation of PFBSA, the devices achieve improved humidity and thermal stability, delivering a power conversion efficiency of 26.05%. This work establishes a molecular‐level synergistic strategy for spiro‐OMeTAD, offering a facile and versatile route to fabricate stable and high‐efficiency perovskite photovoltaics.