This study presents an efficient all-small-molecule organic solar cell (ASM-OSC) processed with non-halogen solvent, achieving high power conversion efficiencies (PCEs) of 15.0% in binary devices and 16.1% in ternary devices under thermal annealing. The key innovation is the design of a small molecule donor, BM-ClEH, which utilizes intramolecular chlorine-sulfur non-covalent interactions to enhance molecular pre-aggregation in tetrahydrofuran (THF), leading to improved micromorphology and exciton dissociation. In contrast, BM-HEH, without such interactions, shows poor pre-aggregation and low PCE due to disordered π-π stacking and phase separation. The study highlights the importance of strong aggregation properties in SMDs for efficient non-halogen solvent-processed ASM-OSCs. The research addresses the challenge of replacing halogen solvents in OSC processing, which are toxic and energy-intensive. Non-halogen solvents like THF are explored for their compatibility with SMDs, but their effectiveness depends on the molecular design of SMDs. BM-ClEH, with a longer alkyl chain on the rhodamine group, exhibits good solubility in THF and maintains strong aggregation properties, enabling stable pre-aggregation and favorable film-forming morphology. This results in enhanced charge transport and reduced recombination in the active layer, leading to higher PCEs. The study also investigates the impact of different solvents on the molecular packing and charge transport properties of SMDs and acceptors. THF processing leads to weaker π-π stacking compared to chloroform (CF), but BM-ClEH's strong aggregation property compensates for this, maintaining good film morphology. The use of thermal annealing (TA) and solvent vapor annealing (SVA) further enhances the performance of THF-processed devices by improving molecular ordering and interfacial interactions. The ternary device incorporating B1 as a guest donor significantly improves the PCE of THF-processed ASM-OSCs, achieving 16.1% under TA. This demonstrates the potential of non-halogen solvent processing for high-performance ASM-OSCs, with BM-ClEH-based devices showing competitive PCEs compared to those using halogen solvents. The study provides valuable insights into the design of SMDs with strong aggregation properties for efficient non-halogen solvent-processed OSCs.This study presents an efficient all-small-molecule organic solar cell (ASM-OSC) processed with non-halogen solvent, achieving high power conversion efficiencies (PCEs) of 15.0% in binary devices and 16.1% in ternary devices under thermal annealing. The key innovation is the design of a small molecule donor, BM-ClEH, which utilizes intramolecular chlorine-sulfur non-covalent interactions to enhance molecular pre-aggregation in tetrahydrofuran (THF), leading to improved micromorphology and exciton dissociation. In contrast, BM-HEH, without such interactions, shows poor pre-aggregation and low PCE due to disordered π-π stacking and phase separation. The study highlights the importance of strong aggregation properties in SMDs for efficient non-halogen solvent-processed ASM-OSCs. The research addresses the challenge of replacing halogen solvents in OSC processing, which are toxic and energy-intensive. Non-halogen solvents like THF are explored for their compatibility with SMDs, but their effectiveness depends on the molecular design of SMDs. BM-ClEH, with a longer alkyl chain on the rhodamine group, exhibits good solubility in THF and maintains strong aggregation properties, enabling stable pre-aggregation and favorable film-forming morphology. This results in enhanced charge transport and reduced recombination in the active layer, leading to higher PCEs. The study also investigates the impact of different solvents on the molecular packing and charge transport properties of SMDs and acceptors. THF processing leads to weaker π-π stacking compared to chloroform (CF), but BM-ClEH's strong aggregation property compensates for this, maintaining good film morphology. The use of thermal annealing (TA) and solvent vapor annealing (SVA) further enhances the performance of THF-processed devices by improving molecular ordering and interfacial interactions. The ternary device incorporating B1 as a guest donor significantly improves the PCE of THF-processed ASM-OSCs, achieving 16.1% under TA. This demonstrates the potential of non-halogen solvent processing for high-performance ASM-OSCs, with BM-ClEH-based devices showing competitive PCEs compared to those using halogen solvents. The study provides valuable insights into the design of SMDs with strong aggregation properties for efficient non-halogen solvent-processed OSCs.