Influence of the number and type of the electron-withdrawing groups of the benzene substituted perylene diimide at the imide position on the optoelectronic performance in the solution/solid

It is generally believed that the photoelectric properties of perylene diimide derivatives are more dependent on the substituent groups at the perylene core than on amine-position substituents. Here, we focus on the relations between the amine-position substituents' features, material state, and the perylene diimide's photoelectric properties. Three perylene diimide derivatives were designed. Their amine-position substituents are 2,3,5,6- fluorobenzene (FFPDI), 2,3,4,5,6-fluorobenzene (BFPDI) and 2,3,5,6-fluorine, 4-trifluoromethyl-benzene (TFPDI), respectively. BFPDI is more affected by solvation than the other two PDIs based on the normalized UV spectrum and enthalpy change caused by solvent. In dilute solution, these PDIs show similar spectra features in absorption and emission, TFPDI film shows the characteristic absorption of H-type aggregates, and other PDIs films show the characteristic absorption of J-type aggregates. The different stacking modes of PDIs result in the difference in the film's electronic structure and carrier mobility. It indicates that increasing the steric hindrance and reducing the number of F atoms have similar effects in solid or solution conditions; however, the appropriate increase in steric hindrance is more beneficial to improve the solvent resistance of the material and enhance the intermolecular dipole interaction in the solid state.