Molecularly Regulated Dynamic Interfaces in 3D/2D Perovskites Enabled by Functional Pyridinium Ionic Liquids

ABSTRACT Perovskite solar cells (PSCs) have rapidly approached the performance limits of established photovoltaic technologies, yet their long‐term operational stability remains a persistent bottleneck for real‐world deployment. By introducing 1‐butyl‐4‐methylpyridinium tetrafluoroborate (BMPyBF 4 ) as a molecular additive, the perovskite interface demonstrated simultaneous defect passivation and energetic reconfiguration, leading to markedly improved charge transport. At an optimal concentration (0.5 mmol%), BMPyBF 4 ‐incorporated PSCs achieve a remarkable open‐circuit voltage ( V OC ) of 1.18 V, a short‐circuit current density ( J SC ) of 24.37 mA/cm 2 , a fill factor (FF) of 82%, and a champion power conversion efficiency (PCE) of 23.6%, significantly outperforming the control device (21.7%) and a state‐of‐the‐art imidazolium‐based IL (BMIMBF 4 )‐doped device (22.6%). Transient absorption spectroscopy (TAS) measurements further corroborate these results by revealing modified carrier dynamics and suppressed recombination in BMPyBF 4 ‐treated films, consistent with improved interfacial charge dynamics. Furthermore, stability assessments demonstrate a profound impact of BMPyBF 4 ; while the reference device loses 33% of its initial efficiency after 500 h of operation, BMPyBF 4 ‐modified PSCs retain 99% of their initial performance even after 1000 h. Similar improvements are observed under thermal stress at 65°C. These findings position pyridinium ILs as multifunctional interfacial regulators capable of simultaneously controlling defect chemistry, charge transport, and device stability.