Process in π-Conjugated Self-Assembled Monolayers for Inverted Perovskite Solar Cells

Self-assembled monolayers (SAMs) are emerging as mainstream and premier hole-selective contacts in inverted perovskite solar cells (PSCs), but their ultrathin monolithic architecture introduces critical challenges, including photothermal instability, susceptibility to desorption and the molecular agglomeration phenomenon, which stem from weak intermolecular interactions and low molecular weight. Among them, π-conjugated SAMs have evolved into the dominant paradigm for the self-assembled molecule design. By enhancing molecular rigidity and intermolecular interactions, most of the π-conjugated SAMs can facilitate ideal molecular packing and interfacial properties to alleviate the above-mentioned SAMs' issues. This review systematically categorizes the π-conjugated SAMs based on their structural component, derivative moieties, functional mechanisms, and highlights the representative works along their development. We believe this work will deepen the fundamental understanding of the relationship governing SAMs' π-conjugation design and their device performance, while providing guidance for the design of novel π-conjugated SAMs to develop efficient and stable inverted PSCs in the future.