In this study, the inorganic thin-film passivation layer was newly adopted to protect the organic layer from moisture and oxygen. Using the electron beam evaporation system, the various kinds of inorganic thin-films were deposited onto the organic layer and their interface properties between organic and inorganic layer were investigated. In this investigation, the MgO layer showed the most suitable properties, and based on this result, the time dependent emission properties were estimated for the OLED with and without passivation layer. In this experiment, we can see that the time-dependent emission properties of MgO passivated OLED had longer life-time compared to non-passivated OLED. Therefore, we can consider that the MgO thin film is one of the most suitable candidates for the thin-film passivation layer of OLED.