A Triphenylamine‐Functionalized Co‐Assembly Material for Record Efficiency Inverted CsPbI3 Perovskite Solar Cells

High quality distribution and surface modification of self‐assembled monolayer (SAM) is crucial for enhancing the efficiency and stability of p‐i‐n inverted perovskite solar cells (PSCs). In this work, a new co‐assembly material, 4‐(aminomethyl)‐N,N‐diphenylaniline iodide (TPAI), is developed to make SAMs orderly assembled. Density functional theory (DFT) calculation and sum frequency generation (SFG) characterization unveil that TPAI can bind with SAMs through π‐π interactions to effectively diminish SAMs aggregation and improve the orderly assembly of SAMs. In addition, Fourier transform infrared spectroscopy (FTIR), X‐ray photoelectron spectra (XPS), and scanning electron microscopy (SEM) characterizations confirm that the co‐assembly TPAI could bind with upward perovskite by –NH3 and Pb interaction for spreading the perovskite solution and improving the quality of perovskite film. The obtained favorable buried interface between SAMs and perovskite augmented hole extraction and transfer capability. Consequently, the TPAI‐treated CsPbI3 PSCs achieve a high VOC of 1.26 V, and a power conversion efficiency (PCE) of 21.60%, the highest reported PCE for inverted CsPbI3 PSCs, maintaining 96.71% initial PCE after tracking at maximum power point (MPP) for 1400 h.