Patterning techniques for polymer light-emitting devices

Organic light-emitting devices (OLED) based on emissive polymeric materials have gained tremendous attention from industry and academia because of the potential to replace current display technologies. In addition to low fabrication costs, this technology holds the prospect of flexible and light-weight displays; However, the sensitivity of the organic thin film (polymer as well small molecules) to oxygen, water and solvent vapor poses a serious problem for product design because it severely limits available patterning techniques. Once the organic film is deposited, conventional processing (such as photolithography or wet etching) is not possible without damaging the organic film.; Two patterning approaches will be introduced in this thesis which have been developed to avoid any device degradation due to the fabrication process: The first method (large-area dye transfer) discusses the fabrication of three-color devices where the emissive color is defined by the dye introduced into the polymer matrix of the device after the polymer layer has been deposited. The second method focuses on dry etching using a chlorine plasma to pattern the metal cathode layer.; The method of large-area dye transfer for patterning the emissive color of OLEDs using transferred photoresist is introduced. Using a large-area dye diffusion source, the dye is diffused into the emissive layer of the OLED. To locally pattern the emissive color, either a shadow mask or a patterned dye source has to be used. The implementation of both approaches using photolithographic patterning and transferred photoresist is outlined in this thesis.; To pattern the cathode layer, a shadow mask is mostly employed which patterns the cathode metal film during the evaporation process. But it is problematic to obtain very small feature sizes over a large area using this technology. In this thesis we demonstrate that dry processing of OLED to pattern a blanket cathode metal film can be used to obtain very small features despite the incompatibility of the photoresist materials with organic LED materials.