The invention provides an organic electroluminescent device which comprises a substrate, an
anode, a hole transmitting layer, an
electron blocking layer, a light emitting layer, a hole
blocking layer, an
electron transmitting layer and a
cathode, wherein the substrate, the
anode, the hole transmitting layer, the
electron blocking layer, the light emitting layer, the hole blocking layer, the electron transmitting layer and the
cathode are sequentially stacked. The light emitting layer comprises a red and green mixed light emitting layer, an
exciton blocking layer, a yellow light emitting layer and a
blue light emitting layer, wherein the red and green mixed light emitting layer, the
exciton blocking layer, the yellow light emitting layer and the
blue light emitting layer are sequentially stacked on the
electron blocking layer. The light emitting layer is a compound layer structure which is formed by sequentially stacking the red and green mixed light emitting layer, the
exciton blocking layer, the yellow light emitting layer and the
blue light emitting layer. The red and green mixed light emitting layer can expand an exciton composite region. The exciton blocking layer can control and regulate the
energy transfer between a blue light and a
green light. The combination of the red and green mixed light emitting layer, the yellow light emitting layer and the blue light emitting layer can acquire abundant spectra. The
color rendering index of the organic electroluminescent device is high. The invention further provides a preparation method of the organic electroluminescent device.