Fraunhofer IVV – Calculation and measurement of the lag-time of barrier multilayer films with an an Ultra-Permeation Accumulation (UPA) Device
Encapsulation films for organic electronics must have very low permeabilities, be transparent and flexible. To achieve this, alternating organic and inorganic layers are combined. A hurdle in the development of these materials is the complex and time-consuming barrier measurements. Fraunhofer IVV (Freising, Germany) has developed an Ultra-Permeation Accumulation (UPA) Device to simplify these problems.
With this device, water vapour permeabilities down to ≥ 2×10-5 g m-2 d-1 can be determined. In addition, Fraunhofer IVV develops mathematical-physical models to predict the permeability of high barrier films. In a current study, multilayer films consisting of up to 11 layers of alternating organic and inorganic layers were analyzed. The sorption and diffusion coefficients of the materials were determined. Based on these data, the lag-time and permeability of these barrier films could be calculated. The measured and calculated results were identical. Even measurement times can be reduced by applying the derived equations. Long lag-times can be achieved by organic layers with high sorption coefficient and increased, layer thicknesses between two inorganic layers. The measuring instrument and the models are available to customers of Fraunhofer IVV for the analysis and development of high barrier films.