The race continues, to simplify and lower costs in the manufacturing process of OLEDs for portable displays, TVs and lighting.
Recently scientists discovered a range of conditions using a two-solvent method that can make extremely smooth thin films using electrospray deposition - thereby creating cheaper, brighter OLED devices that use less power.
Combinations of two solvents were used to make the polymer solution, which was stored inside a thin glass capillary with a conductive wire inserted in it.
They applied a high voltage between the conductive wire and the OLED electrodes on the substrate. The solution that sprayed out of the capillary end as atomized droplets was attracted to the substrate by electrostatic force. This creates less wastage as the solution is more precisely applied.
They found that the first solvent evaporated rapidly after the atomization of the solution, leaving a small amount of the second solvent, which has a higher boiling point, in the droplets. When the polymer concentrations were finely tuned, the carefully chosen second solvent enabled the not-quite-dry atomized droplets to form a smooth, continuous film of high quality, over the OLED electrode. Because the films dry quickly on the surface, it should be easy to fabricate multilayer devices without mixing of materials between layers.
The researchers compared this method with the spin-coated films - the preferred fabrication technique for polymer thin films since it does not require very high temperatures. They found that, there new electrospray deposition films, turned on at lower voltages, could support higher current densities, and at low voltages enabled higher pixel intensity.
According to Yutaka Yamagata of the RIKEN Center for Intellectual Property Strategies, Wako, "Using this technology these devices could be manufactured as inexpensively as printing newspapers." He added that, "The advantage of using electrospray deposition is that we can fabricate both smooth films and nanostructured film using the same technology." He also believes one day this advantage "will also be useful in controlling the structure of organic semiconductor junctions for organic solar cells."
For more attend Printed Electronics Asia 2009 or Printed Electronics USA 2009.
