Power conversion efficiency (PCE) of organic solar cells (OSCs) has crossed the 18% mark for OSCs, which are largely fabricated by spin-coating, and the optimal photoactive thickness is limited to 100 nm. To increase reproducibility of results with industrial roll-to-roll (R2R) processing, slot-die coating coupled with a ternary strategy for optimal performance of large-area, thick OSCs is used. Based on miscibility differences, a highly crystalline molecule, BTR-Cl, is incorporated, and the phase-separation kinetics of the D18:Y6 film is regulated. BTR-Cl provides an early liquid-liquid phase separation and early aggregation of Y6, which slightly improves the molecular crystallinity and vertical phase separation of the ternary blends, resulting in high PCEs of 17.2% and 15.5% for photoactive films with thicknesses of 110 and 300 nm, respectively. The ternary design strategy for large-area and thick films is further used to fabricate high-efficiency flexible devices, which promises reproducibility of the lab results from slot-die coating to industrial R2R manufacturing.
Keywords: roll-to-roll processing; slot-die coating; ternary organic solar cells; thick photoactive films.
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