Highly efficient and air-stable inverted organic light-emitting diode composed of inert materials

The feasibility of a highly efficient and air-stable organic light-emitting diode (OLED) was examined. A phosphorescent OLED not containing an air-sensitive material was fabricated by employing an inverted structure with an air-stable electron injection layer. Efficient electron injection from the bottom cathode to the emitting layer was demonstrated from the fact that the device characteristics of the inverted OLED were almost the same as those of a conventional OLED. No dark spot formation was observed after 250 days in the inverted OLED encapsulated by a barrier film with a water vapor transmission rate of 10 −4 g m −2 day −1 .