In Situ Crosslinked Self-Assembled Monolayer as Processing Stable Hole Selective Contact in Perovskite Solar Cells

Self-assembled monolayers (SAMs) have demonstrated remarkable potential in advancing the efficiency and operational stability of p-i-n structured perovskite solar cells (PSCs) for scalable manufacturing. However, nonuniform surface coverage and weak interfacial adhesion of SAMs on substrates remain critical bottlenecks for further performance enhancement. The polar solvent processing steps during PSC device fabrication have been shown to induce desorption of weakly adsorbed SAM molecules. To address this, we developed a novel SAM material bearing in situ crosslinking moieties-4-(5,9-diallyl-7H-dibenzo[c,g]carbazol-7-yl)butyl phosphonic acid (4PADCB-V)-which undergoes rapid polymerization upon UV irradiation. The crosslinked SAM (crs-4PADCB-V) retained structural integrity upon polar solvent exposure, mitigating interfacial defect formation while enhancing charge carrier transport properties and improving perovskite film crystallinity. Consequently, crs-4PADCB-V-based devices achieved a champion power conversion efficiency (PCE) of 26.46% (certified efficiency of 25.96%) and retained 91% of initial efficiency after 1000 h of maximum power point (MPP) tracking under continuous illumination.