OLED Pixel Electrode Adhesion and Reflectance via Composite Layers
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Solution Overview
Problem
In display devices, particularly in top-emission type OLEDs, the formation of pixel electrodes with high reflectance is challenging due to poor adhesion with the insulation surface, often resulting in a decrease in reflectance when attempting to improve formation conditions.
Innovation Solution
A pixel electrode structure comprising a first conducting layer of Mo or Mo alloy, a second conducting layer of Ag or Ag alloy, and a third conducting layer of metal oxide, with a manufacturing method involving etching using a mixed acid solution to maintain adhesion and reflectance, allowing light to pass through the second electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reflecting layer formed from high reflectance material such as Ag is used on a lower layer of transparent electrode, then reflectance is improved, but adhesion with insulation surface becomes poor
Solution Approach 1:
The pixel electrode uses a composite structure with multiple layers: a lower layer transparent electrode (ITO), a reflecting layer (Ag), and an upper layer transparent electrode (ITO). This composite structure allows the Ag layer to provide high reflectance while the ITO layers ensure good adhesion with the insulation surface and enable light transmission, thus resolving the contradiction between reflectance and adhesion.
Solution Approach 2:
The lower layer transparent electrode (ITO) acts as an intermediary between the insulation surface and the Ag reflecting layer. It provides a bonding interface that ensures good adhesion while allowing the Ag layer to maintain its high reflectance properties, thus mediating between the conflicting requirements of adhesion and reflectance.
2Reliability
If formation conditions of reflecting layer are controlled to improve adhesion, then adhesion is improved, but reflectance decreases
Solution Approach 1:
Instead of modifying the Ag layer formation conditions which would compromise reflectance, the invention uses a composite structure where ITO layers are deposited on both sides of the Ag layer. This allows the Ag layer to maintain optimal formation conditions for high reflectance while the ITO layers provide the necessary adhesion to the insulation surface.
Solution Approach 2:
Different layers in the composite structure have different local functions: the lower ITO layer provides adhesion to the insulation surface, the Ag layer provides high reflectance, and the upper ITO layer provides light transmission. This local differentiation of functions allows each layer to optimize its specific property without compromising the others.
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
The solution effectively improves adhesion with the insulation surface while maintaining high reflectance, enabling efficient light emission and reducing the likelihood of reflectance decrease in pixel electrodes.
Implementation Method 1
etching the second conducting layer and first conducting layer using an etching solution including a mixed acid including phosphoric acid, nitric acid and acetic acid
Data Source
AI summary
A display device a display region arranged with a plurality of pixels in a matrix shape, wherein each of the plurality of pixels includes a first electrode including a first conducting layer on the first conducting layer and comprised from Mo or a Mo alloy, a second conducting layer comprised from Ag or an Ag alloy, and a third conducting layer on the second conducting layer and comprised from a metal oxide having conducting properties, the first electrode being arranged corresponding to each of the pixels respectively, a light emitting layer above the third conducting layer and emitting light according to a current supply, and a second electrode above the light emitting layer and allowing at least a part of the light from the light emitting layer to pass through.