Our program in light emitting devices was originally initiated by the U.S. Air Force and explores the the way in which meso-structured nanocomposites (consisting of an ordered nanophase and a conducting polymer host phase), might be utilized to enhance performance of a light emitting device.

The program has developed along two, distinctly different approaches to lighting...

OLEDs

Nanocomposite organic light emitting diodes for robust, high brightness ultralong lifetime operation. This program is examining the role of giant oscillator strength materials in the development of long lifetime emitting technologies and how these might also lead to increased efficiency.

ACTFELs / FIPELs

Novel nanocomposite EL devices that use polarization currents in the generation of light. These deviecs ability to be color tuned, and highly efficient makes them of particular interest for room lighting. The technology, known as ACTFELs (for inorganic light emitters), is relatively old but we use a novel nanotechnology twist to dramatically improve performance. The new FIPEL technology uses organic emitters and works very differently from the ACTFELs.

left: Diagram of our devices, the WFU seal, (bottom), right: a transparent OLED made before the group moved to WFU.

Our program in OLEDs is based upon the use of light emitting polymers such as PFO for colored displays and unique homopolymers synthesized by our synthesis group for use in white light emitters. Carriers injected from the cathode and anode meet in the emissive layer to produce light.  The dynamics and recombination of these carriers are modified through the use of nanocomposites.

AC thin film Electroluminescent Devices. Such devices differ from OLEDs in several important ways. First, this much older lamp design is based on phosphoresence of  materials such as Cu doped ZnS. It is activated by applying an AC electric field across a capacitor filled with the emissive phosphors as is shown in the diagram taken from the web ( right).  Such lamps are inherently lossy because of the dielectric and therefore not very efficient. Thus they have been largely used in displays and signage. However the very poor power efficiency (>5 LPW typically) is somewhat confusing. While admittedly, most dielectrics will have significant loss in the AC field, the commercially available lamps are much lower than one might expect. Our program is designed to investigate how heterogenous dielectrics made from nanocomposites might help to improve this situation while allowing for the natural benefits of the lamp design to be realized; such as low fabrication costs, relative robustness, and quality of light. here are a couple of the lamps made in the group.

But can these really approach the LPWs needed for general illumination?  With modifications to the phosphors, to the dielectrics, and to the lamp design itself, we are achieving several times the efficiencies of commercial lamps and we hope to go higher.

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