Organic light emitting devices (OLED) with the structure of ITO / TPD / Alq 3 / ZnO / Al were prepared by vacuum thermal evaporation method. By establishing multi-layer structure model, we discussed the influence of Alq 3 deposition thickness and ZnO buffer layer on the photoelectric performance of the device, got the relationship of current density and work voltage. The results show that ZnO buffer layer can produce additional dipole energy and reduce the electronic potential barrier of

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... , its best thickness is 3 nm, too thin or too thick will increase the driving voltage, block carriers injected. When the thickness of Alq 3 film is 50 nm, the photoelectric performance is best, current density reaches 100 mA/cm 2 , the increase of Alq 3 thickness will make the electronics through the layer become scarce, affect the compound with holes. The results provide theoretical guidance to optimize the design and increase the performance of OLED.