In Situ Click Chemistry for Energy-Level-Tunable Mixed Self-Assembled Monolayers in Perovskite Solar Cells

Buried interfacial energy alignment critically affects the performance of the inverted PSCs. Achieving an ideal alignment remains challenging as reliable strategies for precisely tuning the electronic structures of individual SAMs are still elusive. Here, we develop an in-situ click chemistry strategy under mild conditions and with high intrinsic reactivity to construct mixed SAMs with tunable energy levels. By modulation of precursor ratios, molecular coupling and energy-level modulation occur simultaneously. This strategy mitigates steric hindrance and competitive adsorption in conventional blending, enabling seamless energy alignment (ΔE = ∼0.01 eV) and improved interfacial properties. Calculations indicate that reduced electron localization in SAMs from this strategy facilitates enhanced charge transport. Optoelectronic characterizations confirm that mixed-SAMs/perovskite interfaces enhance hole extraction and suppress interfacial nonradiative recombination. Using this strategy, PSCs achieve a PCE of 26.83% (certified: 26.46%) and maintain 93% of initial efficiency after 2,000 h (ISOS-L-2), demonstrating universality across various perovskite compositions.