UNIAX has developed a series of ester-substituted soluble poly(para-phenylenes) PPP for use as active layers in blue and violet light emitting diodes (LEDs). The synthetic route is simple, conducive to large scale, and allows for a wide variety of derivatives - making other routes into blue luminescent conducting polymers seem awkward or obsolete. Derivatives have been tailored to have solubility in non-polar solvents such as hexane or in polar solvents such as ethanol. Films spun-cast directly from solution are pinhole-free and transparent, but take on a violet or blue hue in reflected sunlight. Photoluminescent spectra for all derivatives prepared are reported (luminescence energies for some derivates exceed 3.0 eV), and the fabrication of a prototypes LED device using one of these stable room-temperature processible PPP derivatives has been achieved. The goal in developing this preliminary research into a commercially attractive portable display involves purification of the conducting polymer active layers to optimize the efficiency, and to systematically investigate diode characteristics (efficiency, or "brightness," and light emission turn-on voltage) as a function of active layer thickness, nature of the transparent electrode contact, and nature of the metal electron-injecting contact. The research will also include research into synthesizing a green luminescent PPP, making use of the finding that electron- releasing groups red-shift the luminescence.
