Cationic Polarity Facilitation with Tailored Aminopyridine Ligands for Bulkier Defect-Free and Air-Stable Perovskite Solar Cells

Abstract

Defective crystal framework in the bulk of formamidinium (FA)-dominant perovskite, combined with their inferior phase stability, mainly compromises efficiency reliability and environmental robustness in perovskite solar cells (PSCs). Here, 2,6bis(aminomethyl)pyridine (2,6-BAMPy) with strong passivation capability is exploited to construct defect-free perovskite absorber. 2,6-BAMPy effectively minimizes the volatilization of FA materials and suppresses the halide-related defects at the perovskite surface through its terminal ammonium groups. Unlike other aminopyridine derivatives, specific polarity facilitation by 2,6-BAMPy triggers desirable stable-one-type of amidinium cation upon reaction with conjugated FA + , providing rationality in bulkier perovskite optimization. Moreover, unique molecular geometry of 2,6-BAMPy energetically favors the formation of photoactive α-phase perovskite, effectively suppressing the unwanted intermediate phases throughout the crystallization process.As a consequence, the corresponding PSCs fabricated in open-air conditions deliver a champion efficiency of 24.16%. The encapsulated devices retain 91.2% of their initial performance after 2400 hours accelerated damp-heating measurements (85 °C and 85% relative humidity).