Preparation method of electroluminescent device, electroluminescent device and display device

The invention discloses a preparation method of an electroluminescent device, the electroluminescent device and a display device, and the method comprises the steps: carrying out the secondary thermal annealing treatment of a functional layer of the electroluminescent device, thereby removing the internal stress of the functional layer, improving the problem that the functional layer is liable to crack, and improving the yield and photoelectric performance of the device. 本申请公开了一种电致发光器件的制备方法、电致发光器件及显示装置，通过将电致发光器件的功能层进行二次热退火处理，从而去除功能层的内应力，改善功能层容易开裂的问题，提升器件的成品率和光电性能。