Abstract
Al2O3 films have long been widely used as inorganic encapsulation or passivation layers. The Al2O3 single layer, however, exhibits not only a relatively low barrier performance but also poor environmental stability under harsh conditions due to its hydrolysis reaction with water vapor. Thus, to further improve its environmental reliability and barrier performance as a gas diffusion barrier (GDB), the GDB should be newly designed by forming a nanolaminate structure with ultra-thin sublayers. In addition, through the use of a multilayer based on nanolaminate/organic layers, the nanolaminate film can be effectively protected by a SiO2-inserted organic layer. In this study, alternately stacked nanolaminate/silane-based organic layers are proposed. The nanolaminate-based multilayer achieved a water vapor transmission rate (WVTR) of 5.94 × 10−5 g/m2/day under 60°C/90% accelerated conditions. In addition, after a bending test, the nanolaminate-based multilayer showed a WVTR increase by a magnitude of one order under a 0.63% bending strain. The proposed environmentally and mechanically stable hybrid thin-film encapsulation offers a strong potential for the realization of washable, wearable, or flexible displays in the future.
Highlights
Transparent flexible organic light-emitting diodes (TFOLEDs) are currently considered a next-generation display that will revolutionize the current display industry but will create various free-form displays
In the ZnO/Al2O3/MgO nanolaminate (ZAM NL) structure, the Al2O3 sublayers work as a key gas diffusion barrier (GDB) to obtain an excellent barrier performance (Figure S1)
The NL structure helps improve the barrier performance of the barrier film, the Al2O3 sublayer is required as a key GDB for a highly impermeable NL film
Summary
Transparent flexible organic light-emitting diodes (TFOLEDs) are currently considered a next-generation display that will revolutionize the current display industry but will create various free-form displays. Atomic layer deposition (ALD)-based TFEs have made it possible to guarantee a long lifetime and an excellent barrier performance at low temperatures of less than 100°C without OLED degradation [9,10]. Al2O3 ALD films have been used for organic electronics as a gas diffusion barrier (GDB) due to their good barrier performance at a low temperature of less than 100°C for multilayers based on inorganic/organic layers [2,5,11,12]. Han et al reported multilayers based on Al2O3/organic layers as a flexible TFE [11]. MgO ALD films have good water absorption ability, and aluminate phases form at the interfaces, resulting in the corrosion inhibition of the Al2O3 film. The silamer layers effectively protected the ZAM NL against harsh conditions, resulting in a WVTR value of 5.94 × 10−5 g/m2/day under 60°C/90% accelerated conditions
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