“…Because reasonable solubility of PBI in solvent media is required for their application in organic solar cells, long alkyl side chains or bulk substituents at the imide positions of PBI, with little effect on the electronic and optical properties of molecules, have been extensively used to improve the solubility of PBI and to fine-tune the π–π stacking arrangement by introducing other interactions from the imide substituents. − In contrast, electronic properties of PBI are more sensitive to bulk substituents at the perylene core position, which usually results in a distorted π-conjugated plane and reduced π–π stacking as a result of the steric hindrance. , The aggregation of core-substituted PBI, driven by imide–imide H-bonding interactions and reduced π–π stacking as a result of the bulky core substituents has been reported to show outstanding fluorescent properties . For a given PBI, tuning the volume ratio of good/poor solvent is another important factor for controlling the nanoaggregation and supramolecular assembly process in bulk solution. − Good solvents, usually relatively polar aprotic and aromatic solvents (e.g., chloroform, toluene, etc. ), can solubilize PBI by solvating the extended π-conjugated structure, while poor solvents are mostly aliphatic and polar protic solvents [e.g., methanol (MeOH), heptane, etc.…”