Compound, electroluminescent device, preparation method of electroluminescent device and display device

The invention discloses a compound, an electroluminescent device, a preparation method of the electroluminescent device and a display device, the compound comprises Ar, a coumarin group and a linking group B for linking the Ar and the coumarin group, and the Ar is selected from a structural unit comprising aryl and/or heteroaryl; the preparation method of the electroluminescent device comprises the step of preparing a hole transport layer, in the process of preparing the hole transport layer, a hole transport material layer is prepared firstly, the material of the hole transport material layer comprises the compound, then the hole transport material layer is processed under a first illumination condition to enable the hole transport material to form a cross-linked structure, and the hole transport material layer is processed under a second illumination condition to form a cross-linked structure. And preparing an upper-layer functional film on one side of the hole transport material layer, and processing the h