Controlling Doping Preference of Spiro‐OMeTAD for Efficient and Stable Perovskite Solar Cells

ABSTRACT Organic–inorganic hybrid perovskite solar cells (PSCs) offer excellent optoelectronic properties and low‐cost fabrication. However, their commercialization is limited by the instability and slow oxidation of spiro‐OMeTAD induced by the hygroscopic Li‐TFSI and highly volatile tBP dopants. In this work, two commercially available pyridine derivatives, 4‐(dimethylamino)pyridine (DMAP) and 4‐(trifluoromethyl)pyridine (TFMP), are introduced to regulate the Li ⁺ –TFSI ^– environment and improve the doping behavior of spiro‐OMeTAD. Spectroscopic analyses reveal that DMAP strongly interacts with Li ⁺ but exhibits negligible interaction with TFSI ⁻ , thereby suppressing Li ⁺ –TFSI ⁻ dissociation and hindering oxidation. In contrast, the electron‐withdrawing TFMP promotes ion‐pair dissociation through electrostatic interactions with TFSI ⁻ , increasing the availability of free TFSI ⁻ required for efficient doping. As a result, TFMP‐treated spiro‐OMeTAD shows enhanced conductivity and an optimized work function, and TFMP also contributes to perovskite passivation through interactions with Pb ²⁺ . Consequently, PSCs incorporating TFMP achieve a champion power conversion efficiency of 25.92% and exhibit markedly improved operational durability. Notably, under continuous maximum power point tracking (MPPT) at 1‐sun illumination, TFMP‐treated devices retained over 91% of their initial efficiency after 1000 h. These results demonstrate that TFMP not only effectively regulates dopants and accelerates the doping process but also enables excellent long‐term and thermal stability compared to control devices.