Co-deposited inverted perovskite photovoltaics towards 27% efficiency via vertical redistribution of self-assembled-molecules and in-situ crosslinking

Co-deposited perovskite solar cells simplify the fabrication process, yet excessive aggregation of self-assembled molecules (SAMs) during crystallization leads to poor interfacial adhesion, thereby limiting performance and stability. This study designs an asymmetric SAM (PhBr-4PACz) with steric hindrance to mitigate self-aggregation by suppressing the face-to-face stacking of planar conjugated cores, thereby enriching the presence of co-deposited SAMs at the bottom interface with improved interfacial adhesion and coverage. Its deepened energy level by bromine group and observed p-type doping effect further promotes hole extraction and reduces non-radiative recombination. More importantly, 1-Allyl-3-vinylimidazolium chloride was introduced to seal grain boundaries by in-situ crosslinking to suppress the upward diffusion of SAMs under thermal stress and release residual stress. The optimized inverted devices based on this synergistic strategy achieved a certified power conversion efficiency (PCE) of 27.03% and retained over 96% of their initial efficiency after 2000 hours of continuous illumination at the maximum power point tracking (65 °C, ISOS-L-2). A certified PCE of 24.49% was also achieved for small-area flexible devices, showing the compatibility of this co-deposition process on different substrates. Co-deposited perovskite solar cells suffer from self-assemble monolayer (SAM) aggregation that weakens interfacial adhesion and limits performance. Zhuang et al. design an asymmetric SAM and a crosslinking additive to curb aggregation, enabling efficient, stable devices.