Hot Hydrocarbon‐Solvent Slot‐Die Coating Enables High‐Efficiency Organic Solar Cells with Temperature‐Dependent Aggregation Behavior

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 photoactive 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. Highly efficient temperature‐dependent‐aggregation polymer‐based organic solar cells are fabricated by hot slot‐die coating with hydrocarbon solvents. Power conversion efficiencies of 15.2%, 15.4%, and 15.6% are obtained when chlorobenzene, 1,2,4‐trimethylbenzene (TMB), and ortho‐xylene are used, respectively.