OLED Capping Layer Prevents Baking Gas Degradation
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Solution Overview
Problem
The light emission characteristic of organic light emitting diode (OLED) displays deteriorates due to gases generated during the baking process of the interlayer insulating layer, which can degrade the organic emission layer and affect display quality.
Innovation Solution
A display device with an interlayer insulating layer made of organic material without sulfur and lacking photosensitivity, combined with a capping layer of inorganic material, is used. The capping layer is etched to form contact holes aligned with the interlayer insulating layer, preventing gas discharge to the organic light emitting element and reducing aperture ratio loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If an organic material is used for the interlayer insulating layer, then the aperture ratio is improved, but gas is generated during baking which deteriorates the light emission characteristic
Solution Approach 1:
A capping layer is introduced as an intermediary between the organic interlayer insulating layer and the organic light emitting element. This capping layer prevents gas generated during baking of the organic material from reaching and deteriorating the organic light emitting element, while allowing the organic interlayer insulating layer to maintain its low aperture ratio advantage.
2Ease of manufacture
If the interlayer insulating layer has photosensitivity, then it can be patterned easily, but it absorbs light which reduces display quality
Solution Approach 1:
The photosensitivity function is extracted from the interlayer insulating layer itself and transferred to a separate photosensitive layer. This allows the interlayer insulating layer to be made from non-photosensitive organic material that does not absorb display light, while the separate photosensitive layer provides the necessary patterning capability through photolithography.
3Reliability
If sulfur is included in the organic material, then the material properties are improved, but gas generation during baking increases which degrades the organic emission layer
Solution Approach 1:
The chemical composition parameters of the organic material are changed by eliminating sulfur-containing compounds. Alternative organic materials are selected that provide comparable material stability and performance characteristics without the harmful side effect of generating degrading gas during the baking process.
Data Source
AI summary
A display device includes: a substrate on which is disposed: an organic light emitting element which generates and emits light with which an image is displayed; a thin film transistor connected to the organic light emitting element and with which the organic light emitting element is controlled to emit the light; an interlayer insulating layer disposed between the thin film transistor and the organic light emitting element, the interlayer insulating layer including an organic material; and a capping layer disposed between the interlayer insulating layer and the organic light emitting element, the capping layer including an inorganic material. The interlayer insulating layer disposed between the thin film transistor and the organic light emitting element does not have photosensitivity and does not include sulfur.