Angelo Yializis

Self-healing flexible photonic composites for light sources

Besides display application, organic light emitting diodes (OLED) have great potential for the application of thin film light sources. The new device is designed to have a self-healing mechanism against electrical shorts. The entire device can be prepared in a vacuum chamber equipped with plasma treater, monomer evaporators, radiation curing units and inorganic deposition stations. A blend of small electron-donor organic molecules and radiation polymerizable monomers is flash evaporated to provide a molecular-level vapor-phase mixture, which is then condensed and cured on a flexible ITO coated substrate. The procedure is repeated with an electron-acceptor organic substance, which is deposited over the electron-donor layer. A metallic cathode is then deposited over the electron-acceptor layer and the composite OLED product is packaged. The flash evaporation vacuum deposition technique with in-line radiation cross-linking allows the mixing of small OLED molecules with monomers or oligomers at any ratio. Using this technique, a heterogeneous blend can be flash evaporated and molecularly mixed in the vapor phase, re-condensed as a homogeneous film, and then quickly cross-linked before any phase separation occurs. This creates a unique polymer chemistry that is not possible by conventional coating techniques. The electrical characteristics and the thickness of the metallic cathode and the composition of the polymer layers are selected to produce a self-healing mechanism via gasification of elemental carbon generated by dielectric breakdowns and the oxidation of any exposed cathodic surface, thereby providing a self-healing mechanism to prevent propagation ofthe damage caused by electrical shorts.

ADVANCED CAPACITORS FOR AIRBORNE PULSED HIGH POWER MICROWAVE

The development of a high voltage pulsed power circuit could conceivably be one of the larger technical challenges to realizing the concept of an airborne pulsed high power microwave (HPM) weapon system. Storage of the necessary energy for burst-mode operation of a pulsed HPM is a critical function of the electrical power circuit. Due to volume and weight constraints on airborne platforms, higher energy density capacitors will be necessary for pulsed HPM power systems. Approaches for improving the capacitor energy density are discussed including advanced high permittivity, high stress dielectric materials as well as improved device configuration and packaging.