Strengthening Doped Spiro‐OMeTAD With Organic Synthesis Intermediates (1‐Hexylimidazole) Toward Efficient and Stable Perovskite Solar Cells

Abstract The stability of n‐i‐p perovskite solar cells is fundamentally constrained by the Spiro‐OMeTAD hole transport layer (HTL), which relies on LiTFSI doping for enhanced electrical conductivity and tBP incorporation to solubilize LiTFSI. However, the inherent volatility of tBP compromises its long‐term Li+ chelation capacity, resulting in Li+ aggregation and subsequent hydration‐driven formation of hydrophilic pores, which propagate moisture infiltration pathways, exacerbating perovskite film instability. To address this limitation, a novel ionic chelator, 1‐hexylimidazole (HD), is developed as a tBP alternative. HD's superior dipole moment (4.50 D vs tBP's 2.87 D) and enhanced Li+ chelation capability enable persistent Li+ coordination, suppressing ion migration, agglomeration, and pore nucleation. The HD‐modified HTL exhibits improved morphological uniformity, compactness, and interfacial compatibility with both the perovskite layer and counter electrode. Furthermore, the refined energy‐level alignment at the perovskite/HTL interface contributes to an increase in open‐circuit voltage. HD‐regulated CsFAMA‐based and FA‐based devices achieve power conversion efficiencies of 23.21% and 26.04% (the highest value in dopant engineering for Spiro‐OMeTAD‐based devices to date), with a 23.62% efficiency demonstrated for 1 cm 2 active‐area devices. Remarkably, the optimized devices exhibit exceptional stability under low‐humidity (<10% RH), thermal (85 °C), and continuous illumination (AM 1.5G) conditions, underscore their viability for commercialization.