Rigid Symmetric Aromatic Dithiourea Passivation with Strong Intrinsic Dipole for 21.72%‐Efficient SnO 2 ‐Based Inorganic Perovskite Solar Cells

ABSTRACT CsPbI 3‐x Br x inorganic perovskite solar cells (IPSCs) exhibit excellent intrinsic thermal stability and optoelectronic properties, showing great potential for tandem and space photovoltaics. Nevertheless, iodide oxidation and migration induce undercoordinated Pb 2 + defects that act as non‐radiative recombination centers and deteriorate device performance. Herein, we rationally designed a rigid symmetric aromatic molecule, N,N''‐1,4‐phenylene bisthiourea (1,4‐PBTU), as an effective top‐surface passivator. Its strong intrinsic dipole stabilizes iodide ions against oxidation, while hydrogen bonding suppresses iodide migration. Dual thiourea moieties offer four coordination sites for robust multidentate chelation with undercoordinated Pb 2 + , greatly lowering defect density. The rigid backbone inhibits molecular migration and desorption for long‐term passivation. Furthermore, hydrophobic phenyl skeletons coupled with bisthiourea redox centers realize dual‐mode protection of the perovskite via physical isolation and chemical reduction. Consequently, the optimized SnO 2 ‐based CsPbI 3‐x Br x IPSCs deliver a champion efficiency of 21.72%, the highest value among SnO 2 ‐based counterparts to date. Unencapsulated devices retain over 95% of their initial efficiency after 1200 h under N 2 , and still maintain above 90% after 800 h at 65°C. Impressively, 1,4‐PBTU also exhibits superior performance to traditional organic ammonium passivators. This work offers a universal guideline for designing rigid conjugated polydentate passivators with strong intrinsic dipoles.