Organic Transparent Electrodes Applied to Polymer Light Emitting Diodes

Abstract

Transparent electrodes are widely used in touch panels, solar cells, displays and lighting devices. Developing materials to replace indium tin oxide (ITO) is accelerated from the viewpoint of cost and resources. We developed organic conductive films based on poly (3,4-ethylenedioxythiophene)-poly(styrene sulfonate). The ITO-free organic transparent electrodes were applied to polymer organic light emitting diodes (OLEDs). Solutions of the conductive electrodes and light emitting materials were spin-coated successively on transparent substrates, followed by vacuum deposition of cathode, LiF and Al. We found that the organic conductive films made a good electrical contact to metals, but poor contact (high resistance) with some organic conductors, e.g., conductive glues of conductive metal tapes. Making use of this property, we could construct OLEDs without patterning transparent electrodes (anode), unlike the widely used ITO electrodes which require patterning for device applications to avoid short-circuit. Because electric insulation is automatically made with our films, the device fabrication process will be drastically simplified. [DOI: 10.1380/ejssnt.2014.57]