Buried Interfacial Modification and Light Management for Self‐Assembled Molecules–Based Perovskite Solar Cells

For self‐assembled molecule (SAM)‐based inverted perovskite solar cell, the buried interface (SAM/perovskite interface) significantly determines the overall efficiency and stability of the device, which requires meticulous modulation. In this work, a series of phthalimide derivatives (namely 4‐(1,3‐dioxoisoindolin‐2‐yl)butan‐1‐ammonium iodide [DBAI], 2‐(1,3‐dioxoisoindolin‐2‐yl)ethan‐1‐ammonium iodide [DEAI], and 6‐(1,3‐dioxoisoindolin‐2‐yl)hexan‐1‐ammonium iodide [DHAI]) are developed as buried interfacial modification materials to improve the surface homogeneity, optimize perovskite morphology, and passivate defect sites. Among them, the DHAI with the longest alkyl chain outperforms the others, which is attributed to the steric and electronic effect of the molecular structure. Intriguingly, these interfacial modification materials can introduce ‘island‐like’ morphology on the hole‐selective layer, which significantly boosts the transmittance and perovskite absorption, resulting in substantially enhanced short‐circuit density and power conversion efficiency of 24.71%. These findings reveal the structure–property–performance relationship of these materials and propose a novel strategy for light management at the buried interface.