Electron mobility of two fluorinated perylene diimide compounds was measured by the method of space-charge-limited current: one was N,N'-bisperfluorophenyl-3,4,9,10-perylenetetracarboxylic diimide (1), the other was N,N'-bis(1,1-dihydroperfluorooctyl)-3,4,9,10-perylenetetracarboxylic diimide (2). Electron mobility of compound 2 was found to be 1～2 orders of magnitude higher than that of compound 1. Through UV-Vis, XRD, SEM and AFM characterizations, the difference in electron mobility between 1 and 2 can be ascribed to the distinguished aggregate structures originated from different fluorinated substituents: for 1, the angle between the perylene nucleus ring and the perfluorophenyl ring is big, the planarity of perylene diimide molecule is disrupted, the steric hindrance of the rigid fluorinated phenyl ring is large, meaning that compound 1 molecules can not be stacked to crystallize by overlapping of neighboring perylene rings, and as a result, 1 molecules can be stacked randomly to yield an amorphous film, while in contrast, fluorinated terminal substituent of 2 is flexible zigzag alkyl chain with much smaller steric hindrance, so that 2 molecules can form a crystalline film through p-p interactions of successive perylene rings, which will favor electron transport by hopping between molecules.

Key words: electron mobility, perylene diimide, fluorination, aggregate structure