Hybrid organic-inorganic GaN LED based color downconversion for displays

Abstract

The availability of small short wavelength III-N light sources have opened up new possibilities for applications involving color conversion. As a new application, we consider the hybrid organic-inorganic structure which consists of a GaN based LED emitting in the blue to uv coupled with an organic thin film with high fluorescence efficiency. Upon operation, the organic film absorbs the electroluminescence and emits in the green to red, resulting in color down conversion. Such a hybrid device is simple and has potential application as units for small full color pixelated displays for mobile applications. An array of identical GaN light emitters may be used as a substrate for deposition and patterning of appropriate emissive organic layers to form a full color display. Advantages over fully organic displays is that the electrical transport is confined to the robust GaN part, since organic films have poor electrical transport properties and degrade under electrical operation due to moisture. Advantages over fully semiconductor based displays is that different LEDs emitting different wavelengths do not have to be pieced together: the GaN LED is used as a skeleton to which an appropriate organic layer is simply added for the desired color. We demonstrate the operation of such hybrid LED units and discuss applicability for displays.