The ternary strategy, introducing a third component into a binary blend, opens a simple and promising avenue to improve the power conversion efficiency (PCE) of organic solar cells (OSCs). The judicious selection of an appropriate third component, without sacrificing the photocurrent and voltage output of the OSC, is of significant importance in ternary devices. Herein, highly efficient OSCs fabricated using a ternary approach are demonstrated, wherein a novel non‐fullerene acceptor L8‐BO‐F is designed and incorporated into the PM6:BTP‐eC9 blend. The three components show complementary absorption spectra and cascade energy alignment. L8‐BO‐F and BTP‐eC9 are found to form a homogeneous mixed phase, which improves the molecular packing of both the donor and acceptor materials, and optimizes the ternary blend morphology. Moreover, the addition of L8‐BO‐F into the binary blend suppresses the non‐radiative recombination, thus leading to a reduced voltage loss. Consequently, concurrent increases in open‐circuit voltage, short‐circuit current, and fill factor are realized, resulting in an unprecedented PCE of 18.66% (certified value of 18.2%), which represents the highest efficiency values reported for both single‐junction and tandem OSCs so far.

Organic solar cells (OSCs) technology is regarded as one of the most promising sustainable and green energy sources for their promise as environmentally friendly and easily printable devices. [1-6] In recent years, bulk-heterojunction (BHJ) OSCs Organic solar cells (OSCs) have made rapid progress in terms of their development as a sustainable energy source. However, record-breaking devices have not shown compatibility with large-scale production via solution processing in particular due to the use of halogenated environment-threatening solvents. Here, slot-die fabrication with processing involving hydrocarbon-based solvents is used to realize highly efficient and environmentally friendly OSCs. Highly compatible slot-die coating with roll-to-roll processing using halogenated (chlorobenzene (CB)) and hydrocarbon solvents (1,2,4-trimethylbenzene (TMB) and ortho-xylene (o-XY)) is used to fabricate photo active films. Controlled solution and substrate temperatures enable similar aggregation states in the solution and similar kinetics processes during film formation. The optimized blend film nanostructures for different solvents in the highly efficient PM6:Y6 blend is adopted to show a similar morphology, which results in device efficiencies of 15.2%, 15.4%, and 15.6% for CB, TMB, and o-XY solvents. This approach is successfully extended to other donor-acceptor combinations to demonstrate the excellent universality of this method. The results combine a method to optimize the aggregation state and film formation kinetics with the fabrication of OSCs with environmentally friendly solvents by slot-die coating, which is a critical finding for the future development of OSCs in terms of their scalable production and high-performance.

During the past decade, solution-processed bulk-heterojunction (BHJ) organic solar cells (OSCs) have made great strides and power conversion efficiencies (PCEs) over 16% have been achieved. [1-6] However, the PCEs of top-performing

Ternary strategy has been proved to be an efficient approach to improve the power conversion efficiency (PCE) of organic solar cells (OSCs). However, little attention has been paid to deriving...

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