Transparent conductive thin-film encapsulation layers (Presentation Recording)

Abstract

Gas diffusion barriers (GDB) are inevitable to protect sensitive organic materials or devices against ambient gases. Typically, thin-film gas diffusion barriers are insulators, e.g. Al2O3 or multilayers of Al2O3/ZrO2, etc.. A wide range of applications would require GDB which are at the same time transparent and electrically conductive. They could serve as electrode and moisture barrier simultaneously, thereby simplifying production. As of yet, work on transparent conductive GDB (TCGDBs) is very limited. TCGDBs based on ZnO prepared by atomic layer deposition (ALD) have been reported. Due to the chemical instability of ZnO, it turns out that their electrical conductivity severely deteriorates by orders of magnitude upon exposure to damp heat conditions after very short time. We will show that these issues can be overcome by the use of tin oxide (SnO2). Conductivities of up to 300 S/cm and extremely low water vapor transmission rates (WVTR) on the order of 10-6 g/(m2 day) can been achieved in SnOx layers prepared by ALD at low temperatures (<150°C). A sandwich of SnOx/Ag/SnOx is shown to provide an average transmittance of 82% and a low sheet resistance of 9 Ohm/sq. At the same time the resulting electrodes are extremely robust. E.g., while unprotected Cu and Ag electrodes degrade within a few minutes at 85°C/85%rH (e.g. Cu lost 7 orders of magnitude in electrical conductivity), sandwich structures of SnOx/(Cu or Ag)/SnOx remain virtually unchanged even after 100 h. The SnOx in this work will also provide corrosion protection for the metal in case of harsh processing steps on top these electodes (e.g. acidic). We demonstrate the application of these TCGDBs as electrodes for organic solar cells and OLEDs.