Organic Light-Emitting Device Protective Layer Stress Management
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Solution Overview
Problem
Existing organic light-emitting devices face challenges with moisture and oxygen penetration, leading to delamination and defects, particularly in thin film structures where pixel isolation films create uneven surfaces and stress, resulting in voids and cracks in protective layers.
Innovation Solution
A method involving a sequential deposition of protective layers using sputtering and atomic layer deposition (ALD) techniques, where a first protective layer is formed by sputtering and a second and third protective layer are formed by ALD, with the third layer on the back surface to mitigate stress and prevent crack formation, ensuring high-density layers with alternating low-density layers for enhanced moisture resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer is formed by sputtering or plasma-enhanced CVD method, then the protective layer can be formed on the electrode, but voids are formed at the growth interface and extend the surface, causing defects
Solution Approach 1:
The protective layer is divided into multiple layers: a first protective layer formed by sputtering or plasma-enhanced CVD, and a second protective layer formed by ALD. This segmentation allows each layer to serve different functions - the first layer provides baseline protection while the second layer seals voids and provides high-quality moisture barrier, resolving the surface uniformity issue.
Solution Approach 2:
The patent uses a composite structure combining materials deposited by different methods (sputtering/CVD materials + ALD materials). This composite approach leverages the advantages of each deposition method - the coverage capability of sputtering/CVD and the conformal quality of ALD - to create a protective layer system that overcomes the void formation problem.
2Reliability
If Al2O3 film is formed by ALD method on silicon nitride or silicon oxynitride film, then high-density protective layer is achieved, but stress of Al2O3 film causes formation of cracks from void portions
Solution Approach 1:
The first protective layer formed by sputtering or plasma-enhanced CVD serves as a cushioning layer that absorbs and distributes the stress from the subsequent ALD-formed second protective layer. This prevents stress concentration at void portions that would otherwise cause cracks, while still achieving high moisture resistance through the ALD layer.
Solution Approach 2:
The patent changes the deposition parameters and material composition between layers. The first layer uses sputtering or plasma-enhanced CVD with specific parameters, while the second layer uses ALD with different parameters. This parameter change allows the first layer to have different mechanical properties that cushion the stress of the second layer, preventing crack formation.
3Measurement precision
If pixel isolation films have steep-sided slope or multiple uneven portions to reduce inter-pixel current leakage, then definition is improved, but voids are easily formed and extend the surface of the protective layer
Solution Approach 1:
The protective layer is segmented into two functional layers: the first layer conforms to the uneven pixel isolation film surface (accommodating the steep-sided structure for good definition), while the second ALD layer provides a planarized, void-free sealing layer. This segmentation allows both good pixel definition and surface uniformity to be achieved simultaneously.
Solution Approach 2:
The first protective layer acts as an intermediary between the uneven pixel isolation films and the second ALD protective layer. It fills and smoothes the uneven portions created by steep-sided pixel isolation films, preventing void formation while maintaining the defined pixel structure underneath.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces crack formation and enhances moisture resistance, maintaining the integrity of the organic light-emitting device even under high humidity and temperature conditions, ensuring reliable operation over extended periods without dark spots.
Implementation Method 1
a first protective layer is formed on the electrode by a sputtering method or a chemical vapor deposition (CVD) method
Implementation Method 2
a second and third protective layer are formed on the first protective layer by an atomic layer deposition (ALD) method
Implementation Method 3
a first protective layer is formed on the electrode by a sputtering method or a chemical vapor deposition (CVD) method
Data Source
Figure 1~2
Figure 3A~3C
Figure 4
AI summary
An organic light-emitting element includes, from a first surface of a substrate in this order, the substrate (1), a lower electrode (8), an organic compound layer (9), an upper electrode (10), a first protective layer (11) containing inorganic material, a second protective layer (12) whose density is higher than the density of the first protective layer (11), and a third protective layer (13) whose density is higher than the density of the first protective layer (11), in which the third protective layer (13) is disposed on a second surface of the substrate (1) opposite to the first surface of the substrate (1).