Processing Friendly Slot-die Cast Non-Fullerene Organic Solar Cells with Optimized Morphology

摘要： The power conversion efficiencies (PCEs) of spin-coated organic solar cells (OSCs) have increased rapidly in recent years. However, spin-coating shows poor reproducibility for large-scale production. Slot-die coating, a lab-scale version of roll-to-roll fabrication, has been considered as the most suitable technique for the production of future large-area commercial devices. For this, highly efficient slot-die fabricated devices are required to approach the performance of spin cast OSCs. We present here, a non-fullerene OSC device utilizing PBDB-T:i-IEICO-4F blend, fabricated by slot-die coating without post treatment in the ambient conditions. Device showed an impressive PCE of 12.5%, which is one of the highest reported performance for slot-die coated OSC devices. Compared to spin-coated and blade-coated films with optimized thermal annealing time, the films fabricated by slot-die coating (without any treatment) exhibit not only the highest degree of crystallinity and face-on orientation, but also the smallest domain size and the purest phase, towards enhanced and balanced carrier mobilities. An enhanced excited state charge generation has been attributed from transient charge kinetics using ultrafast spectroscopic signatures. Optimized slot-die coated devices exhibit excellent tolerance for increased thickness of photoactive layer, attributing to favorable molecular packing. We used slot-die coating as one simple fabrication technique, being capable of yielding highly efficient OSCs.