Thickness‐Insensitive Organic Solar Cells with 19.61% Efficiency Processed from All‐Hydrocarbon Solvent and Solid Additive

Abstract Organic solar cells (OSCs) have achieved power conversion efficiencies (PCEs) of >20%, although almost all top‐performance devices having a thin active layer of ≈100 nm and are being processed with environmentally harmful halogenated solvents/additives. However, attempting to fabricate OSCs with thick active layers from non‐halogenated solvents/additives normally leads to dramatically decreased PCEs, seriously restricting their industrialization. To overcome the above shortcomings, it is developed an all‐hydrocarbon‐based system combined with toluene solvent and fluorene (DBP) solid additive to process active layer (PM6:L8‐BO) thickness‐insensitive efficient OSCs. Owing to DBP having good planarity, excellent volatility, and stronger interaction with L8‐BO, its treated active layers exhibit ordered molecular packing, suitable phase separation, and enhanced charge transport, resulting in a superior PCE of 18.64%. Notably, using D18:BTP‐eC9 as the active layer, the OSCs achieve a record‐high PCE of 19.61% among the all‐hydrocarbon‐based system processed devices. Due to the increased crystallinity and optimized hierarchical morphology, the above OSCs show high thickness‐tolerance and provide an excellent PCE of ≈18% with a 300 nm active layer, ranking among the highest PCEs for the all‐hydrocarbon‐based system processed thick‐film devices. This work develop an all‐hydrocarbon‐based system to process active layers in an environmentally friendly way for thickness‐insensitive OSCs, with record‐high PCEs, toward future industrial production.