분자층 증착법을 이용한 유기-무기 복합막 제조 및 박막 봉지 응용 연구

Abstract

The rapid development of organic light-emitting diodes is leading to a paradigm shift from wafer-based technology to the use of plastic substrates, promising flexible displays at a much lower cost. There is one among demanding technologies to realizing flexible OLEDs on plastic substrates, e.g., high efficient thin-film encapsulation with high reliability. In general, the approach of an organic-inorganic hybrid multi-structure is used to accomplish the requirements for ultra-barrier applications. In addition to their barrier properties, these multilayer also have to exhibit high flexibility for many applications. As a fabrication method that can produce high-quality organic-inorganic multilayer thin films is currently in high demand, one promising approach is to use the molecular layer deposition (MLD) technique for organic layers and atomic layer deposition (ALD) for inorganic layers. Both techniques are based on self-limiting, gas-phase surface reactions and can produce very thin, chemically-bound conformal films that are uniform over a large area. The main purpose of this thesis is to develop a barrier thin film based on a novel defect-less inorganic layer, an organic-inorganic nanolaminate, and superlattice thin films by MLD and ALD. In particular, organic-inorganic hybrid thin films exhibit extremely high barrier properties, mechanical reliability, and ultra-stability. First, the organic-inorganic hybrid materials are firstly introduced, and their main fabrication technique as MLD is described in detail. Next, we review the basic principles of water vapor and oxygen permeation through organic and inorganic thin films. The requirement of barrier performance for OLEDs, measurement techniques for permeation rates, and recent developments in basic encapsulation methods are then introduced in detail. Part II presents the fabrication of Al2O3 thin films by UV-enhanced ALD (UV-ALD). A novel UV-ALD method enables to deposit dense and conformal thin film of Al2O3 on a plastic substrate at low-temperature of 40 °C. Defect-less Al2O3 films is obtained under UV irradiation, which demonstrated substantially improved barrier performance for water diffusion. Part III shows a novel barrier thin film based on an organic-inorganic nanolaminate, which consists of alternating nanolayers of self-assembled organic layers (SAOLs) and Al2O3. The SAOLs-Al2O3 thin film enables to achieve an outstanding barrier properties with high flexibility and transparency. Thus, the nanolaminated film was applied to a commercial OLEDs panel as an encapsulation barrier film. The results showed defect propagation could be significant inhibited by incorporating the SAOLs layers, which enhanced the durability of the panel. Finally, Part IV introduces the fabrication of organic-inorganic superlattice thin films for gas-diffusion barriers. The high-quality stable organic monolayers are developed with 4-mercaptophenol (4MP) by MLD. The superlattice thin films fabricated with different ratio of 4MP organic and Al2O3 inorganic layers on rigid and flexible substrates. The barrier properties and flexibilities of the superlattice films are tunable with relative thickness and proportions of organic and inorganic layers.