Top-Emission OELD Buffer Layer Sputtering Damage
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Solution Overview
Problem
Existing organic electroluminescent display (OELD) devices face challenges with low luminance and complex fabrication processes due to the damage caused by sputtering during the deposition of the indium-tin-oxide (ITO) layer, which limits the aperture ratio and requires the use of p-type polycrystalline TFTs.
Innovation Solution
A top emission type OELD device is developed with a buffer layer between the organic luminescent layer and the transparent conductive second electrode, preventing damage during deposition and allowing the use of n-type amorphous silicon TFTs, simplifying the fabrication process and enhancing luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transparent conductive electrode (ITO) is deposited using sputtering, then the electrode can be formed, but the organic luminescent layer is damaged
Solution Approach 1:
A buffer layer is introduced between the transparent conductive electrode (ITO) and the organic luminescent layer. This buffer layer acts as an intermediary that protects the organic luminescent layer from damage during the sputtering deposition process while still allowing the ITO electrode to be formed effectively.
Solution Approach 2:
The buffer layer is deposited in advance before the ITO layer. This preliminary action creates a protective barrier that prevents the harmful effects of sputtering from reaching the organic luminescent layer during the subsequent ITO deposition process.
2Reliability
If p-type polycrystalline TFTs are used, then the device can be fabricated, but the fabrication process becomes complex
Solution Approach 1:
The invention changes the material parameters of the TFT from p-type polycrystalline silicon to n-type amorphous silicon. This parameter change simplifies the fabrication process while maintaining device functionality, as n-type amorphous silicon TFTs can be fabricated using simpler processes compared to p-type polycrystalline TFTs.
3Illumination intensity
If the first electrode is transparent, then light can be emitted from the bottom, but the aperture ratio is limited
Solution Approach 1:
The invention inverts the emission direction by making the second electrode transparent instead of the first electrode. This allows light to be emitted from the top of the device, creating a top-emission OLED structure that achieves higher aperture ratios while maintaining effective light emission.
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 top emission type OELD device achieves high luminance and a higher aperture ratio compared to bottom emission types, while simplifying the fabrication process and reducing production costs by using n-type amorphous silicon TFTs.
Implementation Method 1
the damage caused by sputtering during the deposition of the indium-tin-oxide (ITO) layer
Implementation Method 2
combining the electrons with the holes, generating excitons, and transforming the excitons of an excited state to a ground state
Data Source
AI summary
An organic electroluminescent display (OELD) device includes: first and second substrates facing each other; a plurality of gate lines, a plurality of data lines and a plurality of power lines on the first substrate, the gate and data lines crossing each other to define a plurality of pixel regions; a switching element and a driving element connected to each other in each pixel region; a first electrode connected to the driving element; an organic luminescent layer on the first electrode, the organic luminescent layer including a buffer layer as an uppermost layer; and a second electrode of a transparent conductive material on the organic luminescent layer.