Enhanced moisture barrier performance for ALD-encapsulated OLEDs by introducing an organic protective layer

Abstract

We fabricated inorganic/organic composite film as encapsulation for top-emitting OLEDs, where the inorganic layer was composed of an Al₂O₃/MgO laminated structure prepared by atomic layer deposition (ALD), while the solution-processed polymer (CYTOP, PDMS and SU-8) was fabricated as the organic protective layer. It was found that the optimized inorganic/organic bi-layer structure has better barrier performance, leading to a superior water vapor transmission rate (WVTR) as low as 1.05 × 10⁻⁶ g m⁻² day⁻¹ at 60 °C and 100% R.H., and the encapsulated OLEDs device produces no black spots under a harsh environment (85 °C & 85% R.H.) for 250 h. These improvements were attributed to the hydrophobic surface of the capping polymer lowering the adsorption of water vapor into the bulk material.