The present invention relates to a molecular self-assembled n-type organic semiconductor crystal material. A structural formula of the molecule for self-assembly is selected from a structural formula I; R1 is a substituted alkyl group, a substituent is alkyl group, a substituted position is one of the front nitrogen atoms adjacent to nitrogen atom; or R1 is a linear alkyl group terminally substituted by dialkylamino group; and the n-type organic semiconductor crystal material is two-dimensional monolayer film structure. The application creatively provides a method for preparing the n-type semiconductor crystal material by imide derivative self-assembly. The method is simple and easy to operate; the n-type semiconductor crystal material provided by the invention has high electron mobility; and the prepared photoelectron devices and solar cells have higher efficiency.