Surface-emitting vacuum-deposited organic light emitting device

We demonstrate a novel surface emitting, organic inverted LED (OILED) with a cathode as the bottom contact. This device differs from previously demonstrated surface emitting OLEDs in that it consists entirely of vacuum-deposited molecular organic materials, and contains a crystalline organic layer that protects the underlying hole conducting material from damage incurred during sputter deposition ofthe ITO anode. The OILED can be grown on any smooth surface to which the cathode adheres, such as the drain contact of an n-channel polySi transistor used in active matrix displays. The OILED I-V characteristics and EL spectra are similar to those of conventional OLEDs, while the operating voltage is higher and efficiency somewhat decreased, indicating the need for further optimization of device contacts. Using a semitransparent cathode in the OILED structure grown on a transparent substrate results in a transparent OILED (TOILED), functionally similar to the TOLED structure.