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The use of dopant‐free hole transport layers (HTLs) is critical in stabilizing n‐i‐p perovskite solar cells (pero‐SCs). However, these HTL materials are often processed with toxic solvents, which is not ideal for industrial production. Upon substituting them with green solvents, a trade‐off emerges between maintaining the high crystallinity of the HTL materials and ensuring high solubility in the new solvents. In this paper, we designed a novel, linear, organic small molecule, BDT‐C8‐3O, by introducing an asymmetric polar oligo(ethylene glycol) side chain. This method not only overcomes the solubility limitations in green solvents but also enables stacking the conjugated main chains in two patterns, which further enhances crystallinity and hole mobility. As a result, the n‐i‐p pero‐SCs based on chlorobenzene‐ or green (natural compound) solvent 3‐methylcyclohexanone‐processed BDT‐C8‐3O HTL that without any dopant delivered world‐recorded power conversion efficiencies of 24.11 % (certified of 23.82 %) and 23.53 %, respectively. The devices also demonstrated remarkable operational and high‐temperature stabilities, maintaining over 84 % and 79.5 % of their initial efficiency for 2000 h, respectively. Encouragingly, dopant‐free BDT‐C8‐3O HTL exhibits significant advantages in large‐area fabrication, achieving state‐of‐the‐art PCEs exceeding 20 % for 5×5 cm2 modules (active area: 15.64 cm2), even when processed using green solvents. [ABSTRACT FROM AUTHOR]

The doped Spiro‐OMeTAD hole transport layer (HTL) formed using the lithium bis(trifluoromethane) sulfonimide salt and 4‐tert‐butylpyridine with phenethylammonium iodide surface treatment on a perovskite film has continuously dominated the record power conversion efficiencies (PCEs) of perovskite solar cells (pero‐SCs). However, unstable HTL compositions and iodide salts can cause severe device degradation. In this study, an HTL composition‐conditioning agent (CCA), Spiro‐BD‐2OEG, is designed, which contains a Spiro‐OMeTAD‐like backbone, functional pyridine units, and oligo (ethylene glycol) chains. This finely designed CCA presents good miscibility with Spiro‐OMeTAD and its dopants and acts as a conditioning agent through weak bond interactions. As a result, the CCA‐regulated HTL shows a pinhole‐free and smooth morphology with enhanced Spiro‐OMeTAD ordering and improves dopant stability. In addition, the gradient‐distributed CCA in the HTL can narrow the energy level offset with the valence band of the perovskite. The resultant pero‐SCs exhibit an excellent PCE of 24.19% without any interface treatment and weak size dependence. A remarkable PCE of 22.63% is obtained even for a 1.004‐cm2 device. Importantly, the strategy shows good universality and significantly promotes the long‐term stability of the pero‐SCs based on the classical doped Spiro‐OMeTAD. [ABSTRACT FROM AUTHOR]