Improved compactness of self-assembled monolayers through Coulomb interaction enables highly efficient and stable perovskite solar cells

The deposition of compact self-assembled monolayers (SAMs) presents a significant challenge in the field of inverted perovskite solar cells (PSCs). In this study, we propose a strategy to enhance the compactness of SAMs by strengthening the interactions between SAM molecules and the substrate. Specifically, lithium hydroxide is incorporated into SAM solutions to modify the charge distribution within the SAM molecules. Theoretical simulations indicate a substantial increase in Coulomb interactions among the SAM molecules and the NiO substrate, facilitating the formation of more compact SAM layers under optimized conditions. Experimental results demonstrate that the enhanced compactness significantly improves carrier transport across the SAM layers, resulting in an increase in the champion efficiency of inverted PSCs from 26.0% to 27.3% (with a certified steady-state efficiency of 27.3%). Furthermore, the devices exhibit exceptional operational stability, retaining 94.5% and 93.3% of their initial efficiency after continuous exposure to solar light for 2000 hours at 65°C and 1000 hours at 85°C, respectively, in accordance with the ISOS-L-3 protocol.