The present invention discloses an organic electroluminescent device, and the device comprises a light emitting layer comprising a main material and dye, wherein the doping mass concentration of the dye in the light emitting layer is 1% - 60%. At least one of the dye and the main material has the compound which has the structure shown in the formula I (shown in the description), wherein at most two of R1-R5 are H, and the others are electron-donating groups. The light emitting layer employs a brand-new thermal activation delay fluorescent material, and the single triplet energy level of the material is less than 0.3eV. The material can effectively emit delayed fluorescence, and is high in photoluminescence efficiency. Meanwhile, the material is good in stability, so a high-efficiency and long-service-life thermal activation delay fluorescent device can be obtained.