This study explores the development of all-small-molecule organic solar cells (ASM-OSCs) processed with non-halogen solvents, aiming to improve batch-to-batch reproducibility and commercial potential. The researchers designed and synthesized a small molecule donor, BM-CIEH, which exhibits strong aggregation properties due to intramolecular chlorine-sulfur non-covalent interactions, enhancing molecular pre-aggregation in tetrahydrofuran (THF) and resulting in improved micromorphology after film formation. THF-fabricated ASM-OSCs based on BM-CIEH:BO-4Cl achieved high power conversion efficiencies (PCEs) of 15.0% in binary devices and 16.1% in ternary devices under thermal annealing treatment. In contrast, a weakly aggregated BM-HEH showed poor performance under the same processing conditions due to disordered π-π stacking and indistinct phase separation. This work highlights the importance of strong aggregation properties in non-halogen solvent-processed ASM-OSCs and provides guidance for further development. The study also demonstrates the potential of BM-CIEH in different non-halogen solvents and its compatibility with various acceptor materials, showing promising results for commercial applications.This study explores the development of all-small-molecule organic solar cells (ASM-OSCs) processed with non-halogen solvents, aiming to improve batch-to-batch reproducibility and commercial potential. The researchers designed and synthesized a small molecule donor, BM-CIEH, which exhibits strong aggregation properties due to intramolecular chlorine-sulfur non-covalent interactions, enhancing molecular pre-aggregation in tetrahydrofuran (THF) and resulting in improved micromorphology after film formation. THF-fabricated ASM-OSCs based on BM-CIEH:BO-4Cl achieved high power conversion efficiencies (PCEs) of 15.0% in binary devices and 16.1% in ternary devices under thermal annealing treatment. In contrast, a weakly aggregated BM-HEH showed poor performance under the same processing conditions due to disordered π-π stacking and indistinct phase separation. This work highlights the importance of strong aggregation properties in non-halogen solvent-processed ASM-OSCs and provides guidance for further development. The study also demonstrates the potential of BM-CIEH in different non-halogen solvents and its compatibility with various acceptor materials, showing promising results for commercial applications.