A Triphenylamine‐Functionalized Co‐Assembly Material for Record Efficiency Inverted CsPbI 3 Perovskite Solar Cells

Abstract The precise regulation of self‐assembled monolayer (SAM) distribution and interfacial modification is pivotal for advancing the performance of p‐i‐n inverted perovskite solar cells (PSCs). Here, a new co‐assembly material, 4‐(aminomethyl)‐ N , N ‐diphenylaniline iodide (TPAI), is developed to make SAM orderly assembled. Density functional theory (DFT) calculation and sum frequency generation (SFG) spectroscopy reveal that TPAI binds with SAM via π‐π interactions, effectively suppressing SAM aggregation and enhancing the orderliness of self‐assembly. Further characterization by Fourier transform infrared spectroscopy (FTIR) and X‐ray photoelectron spectroscopy (XPS) demonstrates that ─NH 3 group in TPAI coordinates with undercoordinated Pb 2+ to passivate defects of cesium lead triiodide (CsPbI 3 ) film. The TPAI modification creates a defect‐minimized buried interface with optimized energy alignment, significantly improving hole extraction and transport kinetics. Consequently, the TPAI‐treated CsPbI 3 PSCs achieve a high power conversion efficiency (PCE) of 21.60%, the highest reported value for inverted CsPbI 3 PSCs, maintaining 96.71% initial PCE after tracking at maximum power point (MPP) for 1400 h. This work provides a molecular‐level strategy for interfacial engineering, advancing the development of efficient and durable perovskite photovoltaics.