Top-Emission OELD Transparent Electrode Aperture Ratio
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Solution Overview
Problem
The existing bottom emission type organic electroluminescent display (OELD) devices face issues with luminance, aperture ratio, and a complex manufacturing process due to the direct connection of the anode to the driving element, which can result in short circuits and damage to the organic luminescent layer during fabrication.
Innovation Solution
The implementation of a top emission type OELD device with a transparent conductive electrode as the uppermost layer and an opaque electrode as the lowest layer, incorporating an injection layer between the opaque electrode and the organic luminescent layer to prevent short circuits and using a buffer layer to protect the organic luminescent layer during deposition of the transparent conductive electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a bottom emission type OELD device is used with a transparent first electrode as the anode, then light can be emitted downward through the first electrode, but the aperture ratio is reduced and the manufacturing process becomes complex due to direct connection of the anode to the driving element
Solution Approach 1:
The patent inverts the traditional bottom emission structure by making the second electrode (cathode) transparent and placing it at the top, while the first electrode (anode) becomes opaque and is positioned at the bottom. This inversion allows light to emit upward through the transparent second electrode, increasing the aperture ratio and simplifying the manufacturing process by enabling easier connection of the opaque first electrode to the driving element without requiring transparent connections.
2Device complexity
If the anode is directly connected to the driving element in a bottom emission type OELD, then the device structure is simplified, but short circuits and damage to the organic luminescent layer during fabrication occur
Solution Approach 1:
The patent introduces an injection layer as an intermediary between the first electrode (anode) and the organic luminescent layer. This injection layer serves as a mediator that prevents direct contact and potential short circuits between the anode and the organic luminescent layer, while still allowing efficient charge injection. The injection layer acts as a buffer that protects the organic luminescent layer during fabrication and operation.
3Area of stationary object
If a top emission type OELD device is implemented with transparent conductive electrode as uppermost layer, then aperture ratio is enhanced and manufacturing is simplified, but additional protective measures are needed for the organic luminescent layer
Solution Approach 1:
The patent applies preliminary protective actions by forming the injection layer between the first electrode and the organic luminescent layer before completing the device assembly. This preliminary protective measure ensures that the organic luminescent layer is protected from potential damage during subsequent fabrication steps, particularly during the deposition of the transparent second electrode and other top-layer components.
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 configuration enhances the aperture ratio, simplifies the manufacturing process, and prevents short circuits and damage to the organic luminescent layer, allowing for improved luminance and reduced production costs.
Implementation Method 1
an organic electroluminescent display (OELD) device emits light by injecting electrons from a cathode and holes from an anode into an emission layer, combining the electrons with the holes, generating an exciton, and transforming the exciton from an excited state to a ground state
Data Source
AI summary
An organic electroluminescent display (OELD) device includes first substrate; a plurality of gate lines and a plurality of data lines crossing each other to define a plurality of pixel regions; a power line parallel to and separated from the gate lines; switching and driving elements connected to each other in each of the plurality of pixel regions on the first substrate; a first electrode on the first substrate and connected to one of the driving element; an injection layer on the first electrode; an organic luminescent layer on the injection layer; a second electrode of a transparent conductive material on the organic luminescent layer; and a second substrate attached to and facing the first substrate.