Composition‐Conditioning Agent for Doped Spiro‐OMeTAD to Realize Highly Efficient and Stable Perovskite Solar Cells

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-cm(2) 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.