The Application of <i>π</i> ‐Conjugated Multi‐Pyridyl Molecule for Mitigating Dual‐Interfacial Deficiencies in Inverted Perovskite Solar Cells

ABSTRACT Significant progress of inverted perovskite solar cells (PSCs) primarily focuses on mitigating the deficiencies of specific interface or individual layer via the incorporation of different modification materials, nevertheless, very few studies have utilized identical functional molecules to simultaneously address multi‐interfacial imperfections for the improvement of the device efficiency. Herein, a functional π ‐conjugated multi‐pyridyl molecule 2,6‐bis(3‐pyridyl)‐4‐(4‐pyridyl)pyridine (pytpy) as the modification material is integrated into perovskite/PTAA and PCBM/perovskite interfaces for the mitigation of interfacial deficiencies. Experimental and theoretical studies disclose that pyridyl group of pytpy and phenyl goup of PTAA (or PCBM) can be coupled via π–π interaction, and the N‐donor of pytpy as a Lewis base can interact with the uncoordinated Pb 2+ ion, which improve interfacial contact, optimize energy‐level alignment, passivate perovskite defects and adjust wettability of PTAA. As a result, the inverted PSCs with dual‐pytpy modification achieve an impressive power conversion efficiency (PCE) of 21.50% with an ultra‐low hysteresis index (HI) of 0.16% in contrast with the control device (PCE = 18.83% and HI = 1.16), and also indicate the dramatically enhanced stability. This work proposes a promising strategy for the improvement of the device performance and stability via a multi‐pyridyl molecule dual‐modification at the perovskite/PTAA and PCBM/perovskite interfaces.