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

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 (BMPyBF4) 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%), BMPyBF4-incorporated PSCs achieve a remarkable open-circuit voltage (VOC) of 1.18 V, a short-circuit current density (JSC) of 24.37 mA/cm2, 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 (BMIMBF4)-doped device (22.6%). Transient absorption spectroscopy (TAS) measurements further corroborate these results by revealing modified carrier dynamics and suppressed recombination in BMPyBF4-treated films, consistent with improved interfacial charge dynamics. Furthermore, stability assessments demonstrate a profound impact of BMPyBF4; while the reference device loses 33% of its initial efficiency after 500 h of operation, BMPyBF4-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.