Adaptive O 2 Activation on a Molecular Platform: Promoting Spiro‐OMeTAD Doping for High Efficiency Carbon‐Based Perovskite Solar Cells

ABSTRACT The 2,2’,7,7’‐tetrakis[N, N‐di(4‐methoxyphenyl)amino]‐9,9’‐spirobifluorene (Spiro‐OMeTAD), a widely used hole transport material in perovskite solar cells (PSCs), heavily relies on p‐doping for improving its electrical properties, which is typically achieved through ambient O 2 oxidation. Nevertheless, as a result of the inherent inertness of O 2 toward Spiro‐OMeTAD oxidation, the doping level of Spiro‐OMeTAD remains constrained. In this study, we introduce an effective approach to enhance the doping level of Spiro‐OMeTAD employing the single Ti atoms on carbon nanohorns (CNH) as a molecular platform to activate O 2 , in turn facilitating the oxidation of Spiro‐OMeTAD. The charge transfer between the Ti 1 ‐O 5 moieties and CNH, resulting from strong metal‐support interaction (SMSI), enhances O 2 chemisorption, weakens the O─O bond, and promotes O 2 dissociation, thereby effectively activating O 2 molecules for the oxidation of Spiro‐OMeTAD. Such sufficient oxidation effectively boosts the doping level of Spiro‐OMeTAD, consequently improving its electrical conductivity. Furthermore, the work function of Spiro‐OMeTAD is also well‐modulated, aligning its energy levels more effectively with the carbon electrode. This strategy significantly minimizes energy loss in charge transfer, allowing carbon‐based PSCs to attain a power conversion efficiency (PCE) of 23.85% (certified at 22.85%). Remarkably, the device retains 96.2% of its initial value after 1000 h of continuous illumination.