Transparent organic light emitting devices

We report the demonstration of transparent organic light emitting devices (OLEDs) which are ∼70% transparent throughout the visible spectrum when switched off, and emit light from both sides with a total external quantum efficiency of ∼0.1% when turned on. The devices are Alq3-based single heterostructure OLEDs grown on an ITO-coated glass substrate with a top electrode composed of a very thin layer of Mg–Ag and an overlaying ITO film. The top electrode is both electron injecting and transparent. The transparent OLEDs are expected to be useful in high-resolution full-color displays, as well as for helmet-mounted, windshield-mounted, or other ‘‘head-up’’ display applications.