Towards upscaling of organic photovoltaics using non-fullerene acceptors

Herein, we present our current efforts on fundamental research towards large area organic photovoltaic devices using nonfullerene acceptors (NFAs). First, we present a short review of the main highlights of the state-of-the art in large-area organic solar cells (OSCs) coating. We then present our guidelines to prepare OSCs in an environmentally friendly way from the synthesis of the organic compounds to the choice of the solvent for the coating solutions and the actual OSCs coating. As a starting point, we paired a perylene diimide (PDI) acceptor, PDI₂-EH, to the donor polymer PBDB-T to compare spin-coated and slot-die coated OSC devices. Considering the poor solubility of this bulk-heterojunction system in non-halogenated solvents, we focused our efforts to slot-die coat the soluble PDI₂-EH acceptor on glass and polyethylene terephthalate (PET) substrates from non-halogenated solvents such as toluene, o-xylenes and anisole. We also explored the influence of different UV/ozone treatments for cleaning the PET substrates. Overall, this study presents practical considerations for laying foundations to proceed with an environmentally responsible upscale of OSC coatings.