Organic Light Emitting Device Passivation Layer Hydrogen Diffusion Control
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Solution Overview
Problem
The existing organic light emitting devices face issues with hydrogen (H) diffusion from the passivation layer into the active layer of the thin film transistor, leading to changes in threshold voltage and deterioration of picture quality due to the use of inorganic insulating films deposited by PECVD, which contain high hydrogen content.
Innovation Solution
The implementation of a passivation layer comprising a first inorganic insulating film with a lower hydrogen content and a second inorganic insulating film with a higher hydrogen content, where the hydrogen content in the first film is between 10% and 30%, and in the second film is between 30% and 40%, to minimize hydrogen diffusion while maintaining effective water permeation prevention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an inorganic insulating film is deposited using PECVD to form a passivation layer, then water permeation prevention is improved, but hydrogen content in the passivation layer increases leading to threshold voltage instability
Solution Approach 1:
The passivation layer is divided into multiple inorganic insulating films with different hydrogen content characteristics. The first inorganic insulating film has lower hydrogen content to prevent diffusion into the active layer, while the second inorganic insulating film has higher hydrogen content to provide effective water permeation prevention. This segmentation allows each layer to perform its specific function independently.
Solution Approach 2:
Different regions of the passivation layer are designed with different hydrogen content properties. The first inorganic insulating film (closer to the active layer) has optimized low hydrogen content (10-30%) to protect the active layer, while the second inorganic insulating film (outer layer) has higher hydrogen content (30-40%) for superior water barrier performance. Each layer's composition is locally optimized for its specific protective role.
2Strength
If the deposition temperature is kept below the glass transition temperature of the organic light emitting layer, then the organic light emitting layer is protected from damage, but the hydrogen content in the deposited inorganic insulating film increases
Solution Approach 1:
The passivation structure is segmented into two inorganic insulating films deposited at different temperatures. The first film is deposited at a lower temperature (below Tg) to protect the organic layer, accepting higher hydrogen content. The second film is deposited at a higher temperature to reduce hydrogen content and prevent diffusion. This temporal and functional segmentation of the deposition process resolves the temperature-hydrogen content trade-off.
Solution Approach 2:
The deposition temperature parameter is changed between forming the two inorganic insulating films. The first film is deposited at temperature < Tg of organic layer, while the second film is deposited at temperature > Tg. This parameter change allows optimization of hydrogen content in each layer while protecting the organic light emitting layer from thermal damage during the first deposition.
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 reduces hydrogen diffusion into the active layer, stabilizing the threshold voltage and improving picture quality by optimizing the hydrogen content in the passivation layer, thereby enhancing the overall performance of the organic light emitting device.
Implementation Method 1
H moves downwardly as time passes, and thus H may become diffused into an active layer of the thin film transistor layer 21
Implementation Method 2
the passivation layer 30 serves to prevent water from being permeated into the light emitting device layer 20
Implementation Method 3
The inorganic insulating film such as SiNx may be deposited by plasma enhanced chemical vapor deposition (PECVD)
Data Source
AI summary
An organic light emitting device comprises a first substrate; a thin film transistor layer provided on the first substrate; a light emitting diode layer provided on the thin film transistor layer; and a passivation layer provided on the light emitting diode layer, the passivation layer including a first inorganic insulating film and a second inorganic insulating film, wherein a content of H contained in the first inorganic insulating film is smaller than that of H contained in the second inorganic insulating film.