Flexible organic light emitting devices (FOLED) fabricated on polymer substrates are the next generation display products and associated technologies due to their properties of lightweight, high impact resistance and flexibility. The ideal polymer substrate for FOLED manufacture would combine the gas barrier, thermal and chemical properties of glass with the flexibility, toughness and processability. Due to low barrier performance of polymeric material to moisture and oxygen, the polymer substrate needs to be coated with oxide films. The microstructure of barrier-oxide films is a crucial factor in determining the overall gas barrier performance. Barrier stacks where barrier films are separated by intermediary organic layers serve to decouple or seal the defects. With the development of better gas barrier films, low gas permeation measurement through barrier coated polymer substrates becomes increasingly more important.

Organic light emitting device structures and other polymeric devices degrade in the presence of oxygen and moisture. It is estimated that in OLED to have reliable performance with a lifetime exceeding 10,000 hours, the structure should have an Oxygen Transmission Rate (OTR) of below 10-5cc/m2/day and a Water Vapour Transmission Rate (WVTR) of about 10-6 g/m2/day at 39C and 95% RH conditions. Currently, there is no definite commercial method for measuring water vapour permeation at these levels. A novel moisture-permeation measurement system was developed at IMRE and would be highly suitable for assessing ultra low water vapour permeation levels through ulta high barrier stacks with a high sensitivity.

In this project, we will be studing the water vapor permeation rates through multi-layer oxide barrier stacks fabricated onto the plastic substrates as function of layers and correlated with lamination theory and model. We will be estimating the number of barrier layers required for the multi-layer stacks as per the lamination model.

In addition to the permeation studies, film quality will be characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. This will help to understand the permeation mechanisms of different films based on defects, microstructure and film morphology. Also, attention will be paid to the optical properties of films, particularly for efficient light extraction from encapsulated OLED devices.