Organic light emitting diodes having transparent cathode structures

Abstract

Organic light emitting diodes having a transparent cathode structure is disclosed. The structure consists of a low work function metal in direct contact with the electron transport layer of the OLED covered by a layer of a wide bandgap semiconductor. Calcium is the preferred metal because of its relatively high optical transmissivity for a metal and because of its proven ability to form a good electron injecting contact to organic materials. ZnSe, ZnS or an alloy of these materials are the preferred semiconductors because of their good conductivity parallel to the direction of light emission, their ability to protect the underlying low work function metal and organic films and their transparency to the emitted light. Arrays of these diodes, appropriately wired, can be used to make a self-emissive display. When fabricated on a transparent substrate, such a display is at least partially transparent making it useful for heads-up display applications in airplanes and automobiles. Such a display can also be fabricated on an opaque substrate, such as silicon, in which previously fabricated devices and circuits can be used to drive the display.

Dependencies are inferred from the claim text.