*John Fahlteich, Michiel Top, Stefan Hinze, Uwe Meyer, Tobias Vogt, Valentijn von Morgen, Matthias Fahland, Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, Dresden, Germany
Gas barrier coatings on polymer substrates represent a critical component for flexible electronic devices such as organic solar cells or organic light emitting diodes. Whereas functional films with water vapour transmission rates below 10^-5 g/(m^²d) have been reported recently, remaining challenges are reproducibility of the performance over a set of multiple manufactured rolls as well as maintaining quality and performance in subsequent processing and device integration steps. This paper discusses both intrinsic and extrinsic influence factors on the gas barrier performance of functional films. Mechanical flexibility demands the use of thinnest possible permeation barrier layers with highest performance rendering a layer thickness control during the deposition inevitable. However, inline thickness measurement on transparent and thin layers (< 100 nm) is challenging. This paper discusses solutions for inline thickness evaluation and immediate process adjustments during roll-to-roll reactive sputter deposition of oxide barrier layers are given. The most critical extrinsic factor for gas barrier performance is the formation of defects through particles, mechanical impacts or surface irregularities. Contact with rollers has been identified as major source of layer defects. Optimized machine layouts and improved layer stack design strongly improve yield in roll-to-roll deposition of barrier layers on polymer webs. Finally, reproducible water vapor transmission rates < 5∙10^-4 g(m^²d) are reported for pilot-scale roll-to-roll processing of ZTO gas barrier layers. The barrier films have proven to be robust in subsequent roll-to-roll processing of transparent electrodes and organic devices.