Resilient 3D Cross‐Linked Conductive Carbon Dot Networks for Efficient Flexible Organic Solar Cells With Enhanced Photoelectrical‐Mechanical Stability

ABSTRACT To enable large‐area applications of flexible organic solar cells (OSCs), a novel electron transport layer (ETL) material with excellent high conductivity, outstanding bending performance, and good stability has been developed in this study. These characteristics make the material highly significant in enhancing the performance of flexible OSCs. Through synergistic hydrogen bonding and covalent interactions between the ─COOH/─OH groups on carbon dots (CDs) and the –NH 2 in polyethyleneimine (PEI), a dense three‐dimensional (3D) cross‐linked network is established. This network creates continuous conductive pathways, imparting the material with superior electrical conductivity and excellent thickness tolerance. Furthermore, nano‐sized CDs act as physical crosslinking points, effectively dissipating stress and significantly enhancing mechanical toughness and bend tolerance. As a result, flexible OSCs with this ETL achieve a PCE of 16.24% and retain 91.5% of their initial efficiency after 10,000 bending cycles at a radius of 5 mm, significantly outperforming PEI‐based (51.6%) counterparts, while also demonstrating excellent stability under ambient air and UV irradiation. Moreover, the CDs:PEI‐based flexible OSCs maintain good bending stability and structural integrity even under different bending radius. This solution‐processable material synergistically optimizes optoelectronic and mechanical properties, offering a robust interfacial solution for Roll‐to‐Roll manufacturing of flexible OSCs.