Method of fabricating electrodes

#The present invention relates to the field of organic semiconductor devices, and more particularly to transparent electrodes used in such devices.

#Opto-electronic devices that make use of organic materials are becoming increasingly desirable for a number of reasons. Many of the materials used to make such devices are relatively inexpensive, so organic opto-electronic devices have the potential for cost advantages over inorganic devices. In addition, the inherent properties of organic materials, such as their flexibility, may make them well suited for particular applications such as fabrication on a flexible substrate. Examples of organic opto-electronic devices include organic light emitting devices (OLEDs), organic phototransistors, organic photovoltaic cells, and organic photodetectors. For OLEDs, the organic materials have performance advantages over conventional materials. For example, the wavelength at which an organic emissive layer emits light may generally be readily tuned with appropriate dopants, while it may be more difficult to tune inorganic emissive materials. As used herein, the term “organic material” includes polymers as wells as small molecule organic materials that may be used to fabricate organic opto-electronic devices.

#OLEDs makes use of thin organic films that emit light when voltage is applied across the device. OLEDs are becoming an increasingly popular technology for applications such as flat panel displays, illumination, and backlighting. OLED configurations include double heterostructure, single heterostructure, and single layer, and a wide variety of organic materials may be used to fabricate OLEDs. Several OLED materials and configurations are described in U.S. Pat. No. 5,707,745, which is incorporated herein by reference in its entirety.

#FIG. 1 shows a top-emitting organic light emitting device having a transparent multi-layer top electrode through which light may be emitted.

#FIG. 2 shows a top-emitting organic light emitting device having a transparent multi-layer top electrode, having a structure different from that of FIG. 1, through which light may be emitted.

#FIG. 3 shows a top-emitting organic light emitting device having a transparent multi-layer top electrode, having a structure different from that of FIGS. 1 and 2, through which light may be emitted.

#In an embodiment of the invention, a multi-layer transparent cathode structure is provided. The structure includes a layer of conductive oxide, such as indium tin oxide (ITO), zinc indium tin oxide, or aluminum zinc oxide. The structure may also include an electron injection layer that enhances the injection of electrons from the cathode into the organic layers of the device. The structure may also include an organic buffer layer that protects underlying organic layers during the subsequent deposition of ITO. The structure may also include a conductive layer that enhances the injection of electrons from the ITO layer into other layers of the electrode.

#FIG. 1 shows a top-emitting organic light emitting device 100 having a transparent multi-layer top electrode 140 through which light may be emitted. Device 100 is disposed over substrate 110, and includes a bottom electrode 120, an organic operative layer 130, and a top electrode 140, deposited in that sequence over substrate 110. Top electrode 140 further includes an electron injection layer 150, an organic buffer layer 160, a conducting layer 170, and a transparent conductive oxide layer 180, deposited in that sequence over organic operative layer 130.

#Substrate 110 may be made of any conventional substrate material. Glass, plastic, metal foil, and ceramic substrates are known to the art. Substrate 110 may be rigid or flexible. Substrate 110 may be transparent or opaque. Substrate 110 may be a semiconductor such as silicon, which may facilitate the fabrication of circuitry connected to device 100 onn substrate 110.