Flexible ITO‐Free Organic Solar Modules Using Fully Roll‐to‐Roll Processable Top Illumination Design

Organic photovoltaics (OPVs) have reached above 20% Power Conversion Efficiency (PCE) in recent years. However, all state-of-the-art devices are fabricated using techniques that are largely unsuitable for industry-compatible Roll-to-Roll (R2R) coating methods. In this study, a hybrid approach that combines the advantages of R2R vacuum and solution coating methods for fabricating organic solar modules on glass and flexible polyethylene terephthalate (PET) in a top-illumination configuration is adopted. The opaque bottom electrodes are developed using R2R sputtering to achieve low sheet resistance and reduced surface roughness. The remaining layers in the devices, including top transparent Silver nanowire (AgNWs) anodes, are optimized using the R2R-compatible slot-die coating method at ambient conditions using greener solvents. The best devices on glass substrates achieved a PCE of 13.5%, using this ITO-free scalable OPV architecture. An equally impressive PCE of 12.5% is attained when the devices are scaled up to mini-modules with an active area of 12.8 cm2. Furthermore, six mini-modules on a PET substrate measuring 24 cm x 17 cm are developed, reaching PCE up to 11.5%, the highest reported in this category. This research highlights the potential for developing high-performance, cost-efficient, and mechanically adaptable ITO-free devices using industry-compatible methods.