Organic EL Device Dual-Layer Passivation Void Prevention
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Solution Overview
Problem
Organic electroluminescence (EL) devices face issues with void formation and moisture infiltration due to hydrogen-related reactions during the deposition of passivation layers, leading to degradation and dark spots, especially when alkali metal compounds are used in the electron injection layer.
Innovation Solution
A dual-layer passivation strategy is employed, where a hydrogen-free silicon-based first passivation layer is formed on the upper electrode to prevent hydrogen ion and radical formation, followed by a hydrogen-containing second passivation layer to enhance coverage and moisture resistance, using materials like silicon oxide, silicon nitride, and silicon oxynitride.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passivation layer is formed using hydrogen-containing materials (such as silicon nitride film by CVD or sputtering), then the coverage performance and moisture resistance are improved, but voids occur due to hydrogen ion and radical reactions with alkali metal compounds, leading to device degradation
Solution Approach 1:
The passivation layer is divided into multiple sub-layers: a first passivation layer formed without hydrogen-containing materials (using silicon oxide or silicon oxynitride) to prevent void formation, and a second passivation layer formed with hydrogen-containing materials (such as silicon nitride) to provide superior moisture resistance and coverage. This segmentation allows each layer to perform its specific function without causing the harmful effects that would occur if a single layer attempted to provide both properties simultaneously.
Solution Approach 2:
The first passivation layer acts as an intermediary layer between the organic compound layer containing alkali metal compounds and the second passivation layer containing hydrogen. By placing this hydrogen-free intermediate layer first, it prevents direct contact between hydrogen and alkali metal compounds, thereby preventing the formation of voids while still allowing the second layer to provide its moisture-resistant function.
2Reliability
If the thickness of the passivation layer is increased to improve sealing performance, then moisture and oxygen infiltration is reduced, but cracks and splintering occur in the sealing film
Solution Approach 1:
Instead of using a single thick passivation layer that would crack and splinter, the solution segments the passivation function into multiple thinner layers. The first passivation layer (hydrogen-free) and second passivation layer (hydrogen-containing) are each formed at optimized thicknesses that prevent cracking while collectively providing superior sealing performance. This multi-layer approach distributes the mechanical stress and prevents the formation of cracks that would occur in a single thick layer.
3Ease of manufacture
If vapor deposition or sputtering methods are used to form the passivation layer, then the formation process is simplified, but foreign matter such as clusters and etching residues adhere to the device surface, reducing coverage performance
Solution Approach 1:
The first passivation layer is specifically designed with hydrogen-free composition (using silicon oxide or silicon oxynitride) to provide excellent coverage over foreign matter on the device surface. This localized quality adjustment in the first layer ensures complete coverage without requiring complex formation processes, while the second layer provides additional moisture resistance. The combination maintains ease of manufacture while achieving superior coverage performance.
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 effectively suppresses void generation and prevents moisture or oxygen infiltration into the organic compound layer, significantly reducing the occurrence of dark spots and improving the longevity of the organic EL device.
Implementation Method 1
a first passivation layer which is free of hydrogen and contains silicon as a main component is formed on the upper electrode
Implementation Method 2
a second passivation layer containing hydrogen and silicon as a main component is formed on the first passivation layer
Implementation Method 3
the inside of the resultant is attached with a moisture absorbent so that moisture infiltrating from a sealing surface is absorbed by the moisture absorbent
Data Source
AI summary
Provided is an organic EL device including a substrate, a lower electrode, an organic compound layer containing one of an alkali metal and an alkali metal compound, an upper electrode formed of an oxide film, and passivation layers for covering the lower electrode, the organic compound layer, and the upper electrode, the lower electrode, the organic compound layer, the upper electrode, and the passivation layers being stacked in the stated order on the substrate, in which the passivation layers include a first passivation layer formed on the upper electrode, which contains silicon as a main component, and which is free of hydrogen and a second passivation layer formed on the first passivation layer which contains silicon as a main component and hydrogen.