Light-Emitting Element Electrode with Composite Oxide Layers
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Solution Overview
Problem
Current light-emitting elements face challenges in achieving high emission efficiency, low power consumption, and stable electrode performance due to material compatibility issues and alignment accuracy requirements in manufacturing, particularly in the white EL+color filter method, which results in low light use efficiency and potential electrode corrosion.
Innovation Solution
A light-emitting element structure is proposed with a conductive layer and transparent conductive layers containing indium and other oxides, where the second transparent conductive layer has lower resistivity and greater thickness than the first, and includes a stabilizer to prevent electron and oxygen donation, enhancing reflectance and work function while reducing corrosion risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a material having high reflectance is used for one of the pair of electrodes to improve light extraction efficiency, then light extraction efficiency is improved, but it is difficult to select a stable material which also has high work function
Solution Approach 1:
The patent applies composite materials by stacking multiple electrode layers (first electrode layer, second electrode layer, third electrode layer) where each layer has different functions. The first layer provides high reflectance for light extraction, while the second layer with high work function ensures stable electrical contact and prevents corrosion. This composite structure resolves the contradiction by combining materials that individually satisfy different requirements (reflectance and work function) into a unified electrode system.
2Power
If a metal oxide having a high work function is used for one of the pair of electrodes to reduce voltage loss and drive voltage, then drive voltage is reduced, but light extraction efficiency may be compromised due to lower reflectance
Solution Approach 1:
The patent uses a composite electrode structure where the second electrode layer is made of metal oxide with high work function to reduce drive voltage and prevent corrosion, while the first and third electrode layers provide high reflectance for light extraction. This composite approach allows the system to simultaneously achieve low drive voltage and high light extraction efficiency by distributing different functions across multiple layers.
Solution Approach 2:
The electrode is segmented into multiple functional layers: the first electrode layer handles light extraction (high reflectance), the second electrode layer handles electrical stability (high work function), and the third electrode layer provides additional reflectance. This segmentation allows each layer to be optimized for its specific function without compromising the other functions.
3Productivity
If the white EL+color filter method is used to share EL layers among subpixels, then manufacturing cost is reduced and productivity is increased, but light use efficiency becomes low due to color filter absorption
Solution Approach 1:
The patent applies local quality by creating different electrode structures for different regions: the first electrode layer has high reflectance in regions corresponding to color filters to redirect absorbed light back into the EL layer, while maintaining appropriate optical properties in other regions. This localized optimization reduces light loss without requiring separate EL layers for each color, thus maintaining high productivity while improving light use efficiency.
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 improves light extraction efficiency, reduces drive voltage, and enhances the stability and productivity of light-emitting elements, enabling high-resolution displays with reduced manufacturing costs and increased light use efficiency.
Implementation Method 1
it is preferable to use a material having high reflectance for one of a pair of electrodes, through which light is not extracted
Implementation Method 2
The first transparent conductive layer contains a first oxide. The second transparent conductive layer contains a second oxide
Implementation Method 3
a stabilizer to prevent electron and oxygen donation, enhancing reflectance and work function while reducing corrosion risks
Data Source
AI summary
A light-emitting element including a first electrode, a second electrode, and an EL layer provided between the first and second electrodes is provided. The first electrode includes a conductive layer, a first transparent conductive layer in contact with the conductive layer, and a second transparent conductive layer in contact with the first transparent conductive layer. The first transparent conductive layer contains a first oxide. The second transparent conductive layer contains a second oxide. The conductive layer has a function of reflecting light. The first oxide contains In and M (M represents Al, Si, Ti, Ga, Y, Zr, La, Ce, Nd, or Hf). The second oxide contains In. The resistivity of the second transparent conductive layer is lower than that of the first transparent conductive layer. The thickness of the second transparent conductive layer is greater than or equal to that of the first transparent conductive layer.