PLANAR MICROFABRICATED POLYMER LIGHT-EMITTING-DIODES

Conjugated polymers are organic semiconducting materials that can emit light. These polymers have the advantages of being light, cheap and e asy to process, and in addition the band gap can be tailored. We repor t the microfabrication of surface light-emitting diodes (SLEDs) on sil icon substrates in which the electrodes are underneath the organic ele ctroluminescent layer. Patterned electrodes are separated by a 2500 An gstrom thick insulating layer of silicon oxide or are interdigitated w ith a separation of 10 or 20 mu m; the luminescent polymer is spin coa ted or solvent cast on top of the electrodes. This fabrication method is completely compatible with conventional silicon processing because the polymer is deposited last and the light is emitted from the upper surface of the diodes. Despite the large spacing between electrodes, a nd despite the absence of an evaporated top contact, the Voltages requ ired for light emission were not much greater than those used in conve ntional sandwich-type structures.