Get it white: color-tunable AC/DC OLEDs

Organic light-emitting diodes (OLEDs) have gained considerable attention because of their use of inherently flexible materials and their compatibility with facile roll-to-roll and printing processes. In addition to high efficiency, flexibility and transparency, reliable color tunability of solid state light sources is a desirable feature in the lighting and display industry. Here, we demonstrate a device concept for highly efficient organic light-emitting devices whose emission color can be easily adjusted from deep-blue through cold-white and warm-white to saturated yellow. Our approach exploits the different polarities of the positive and negative half-cycles of an alternating current (AC) driving signal to independently address a fluorescent blue emission unit and a phosphorescent yellow emission unit which are vertically stacked on top of each other. The electrode design is optimized for simple fabrication and driving and allows for two-terminal operation by a single source. The presented concept for color-tunable OLEDs is compatible with application requirements and versatile in terms of emitter combinations.