Pathways to Upscaling Highly Efficient Organic Solar Cells Using Green Solvents: A Study on Device Photophysics in...

As the rise of nonfullerene acceptors (NFA) has allowed lab-scale organic solar cells (OSC) to reach 20% efficiency, translating these devices into roll-to-roll compatible fabrication still poses many challenges for researchers. Among these are the use of green solvent solubility for large-scale manufacture, roll-to-roll compatible fabrication, and, not least, information on charge carrier dynamics in each upscaling step, to further understand the gap in performance. In this work, the reproducibility of champion devices using slot-die coating with 14% power conversion efficiency (PCE) is demonstrated, under the condition that the optimal thickness is maintained. It is further shown that for the donor:acceptor (D:A) blend PM6:Y12, the processing solvent has a more significant impact on charge carrier dynamics compared to the deposition technique. It is found that the devices processed with o-xylene feature a 40% decrease in the bimolecular recombination coefficient compared to those processed with CB, as well as a 70% increase in effective mobility. Finally, it is highlighted that blade-coating yields devices with similar carrier dynamics to slot-die coating, making it the optimal choice for lab-scale optimization with no significant loss in translation toward up-scale.