Moisture permeability through multilayered barrier films as applied to flexible OLED display

Abstract

Strict protection of organic light-emitting diodes (OLEDs) and other optoelectronic materials from direct contact with ambient moisture and oxygen is one of the major challenges in the development of flexible OLED displays and other flexible electronic devices. This problem is typically addressed by the use of polymeric substrates with multilayered barrier coatings comprising alternating organic/inorganic layers. The multilayered barrier approach is critically examined using a numerical model based on a defect-dominated diffusion process combined with experiments involving face-to-face lamination of two barrier films. The modeling results identify two regimes, corresponding to two distinct permeation mechanisms, and provide scaling relationships and general design criteria for multilayered barrier coatings. The results suggest that the most significant gain in barrier performance can be realized when the thickness of the organic/adhesive layer(s) in the multilayered structure is less than the average pinhole (defect) size in the inorganic barrier layer(s).

Research on flexible display at Ulsan National Institute of Science and Technology

“…OLEDs generally require a WVTR of approximately 10 −6 g/ m 2 •per day, which is a very low value compared to inorganic LEDs. 53 A glass "lid" and moisture absorbable getter with a UVcurable epoxy resin in an inert chamber is generally used to encapsulate OLEDs. However, this process cannot be applied to flexible OLEDs because the glass lids used to date are too rigid.…”

Thin-Film Diffusion Barriers for Electronic Applications

“…Complementary to Graff 's study of lag-time in a multilayer barrier stack, Greener et al (38) modeled steady-state permeation for a simple laminate barrier structure and multilayer barrier stacks. The laminate structure consisted of two polymer films, each coated on one side with a thin inorganic barrier layer, laminated together by a thin adhesive that bonded the barrier-coated sides to each other.…”

Low-temperature atomic layer deposition of SiO 2 /Al 2 O 3 multilayer structures constructed on self-standing films of cellulose nanofibrils

“…[16] In addition to the moisture sensitivity control, the nanolaminate structures based on SiO2 and Al2O3 may bring multifunctionality to be utilised e.g. as antireflective and optical materials [17].…”