New Stable Cathode Materials for OLEDs (Phase II)

Investigating Organization
International Technology Exchange

Principal Investigator(s)
Dr. Terje Skotheim, terje.skotheim@intexworld.com, (520) 299-9533

Subcontractor
None

Funding Source
Small Business Innovation R&D, Phase II

Award
DOE Share: $749,824

Contract Period
7/14/04 - 7/13/06

Many of the cathode materials currently in use in Organic Light Emitting Diodes (OLEDs), both for display and general lighting applications, are highly reactive metals, such as Mg, Li and, Ca and alloys, which are unstable and prone to oxidation. This complicates manufacturing and requires complex encapsulation techniques. It has led to reduced lifetimes of the devices.  There is a need to develop cathode materials that have low work function for efficient electron injection, can be coated over large areas with a robust deposition process, and possess a higher degree of environmental stability against oxidation than cathode materials currently in use. This project will develop a new class of nanostructured amorphous carbon cathode coatings that satisfies those criteria.  The materials can be coated on a variety of substrates, as thin films using plasma enhance chemical vapor deposition (PECVD), allow tailoring of the work function over a wide range and are dense to resist the penetation of both oxygen and water. During Phase I, the first examples of this new class of cathode coatings were produced that demonstrated the principle. OLED devices incorporating the nanocomposite films as cathodes were made and tested, and areas for optimization of the composition and deposition conditions were identified.  During the first year of the two-year Phase II project, a specially designed PECVD tool has been be constructed for the deposition of nanocomposite cathode films. In the second year, deposition conditions are being optimized to provide films with varying and controllable work function and efficient electron injection into the organic emitter layer. The films will be analyzed with TEM, X-ray, and photoelectron spectroscopy to determine structure and work function, and tested as cathodes in OLED devices.

Solid state lighting based on OLED devices have the potential to provide highly energy-efficient general lighting. This could effect very substantial energy savings, as much as 10% of the nation's total energy use by some estimates. This technology represents an industry of the future where the U.S. still maintains a technological lead, substantially due to the efficacy of the DOE-funded program. The coatings developed under this Phase II project will become an important enabling technology to realize the potential of OLED-based general lighting. Other applications include OLEDs for displays, particularly displays on flexible substrates.

Content dated 2/08