Organic Light Emitting Display Metal Doped Layer Sputtering Protection
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Solution Overview
Problem
In organic light emitting display elements, the top-emission type structure faces challenges in achieving low sheet resistance for the upper electrode while maintaining high transmissivity and luminance efficiency, as materials with low work function and high conductivity tend to degrade the organic light emitting layer during deposition and cause micro-cavity effects.
Innovation Solution
A metal doped layer is introduced between the organic light emitting layer and the upper electrode, using aluminum-based metals, alkali metals, or alkali earth metals as dopants, which reduces sheet resistance and prevents layer degradation during sputtering, with a charge injection layer formed by chemical vapor deposition to minimize physical impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal with low work function and high electrical conductivity is used as the upper electrode to reduce sheet resistance, then electrical conductivity is improved, but transmissivity to visible light deteriorates and the organic light emitting layer is damaged during deposition
Solution Approach 1:
An organic buffer layer is introduced as an intermediary between the metal cathode and the organic light emitting layer. This buffer layer serves as a mediator that prevents direct contact between the metal deposition process and the organic light emitting layer, thereby protecting the latter from damage while still allowing the metal to function as the upper electrode for electrical conductivity
Solution Approach 2:
The organic buffer layer is formed in advance before depositing the metal cathode material. This preliminary action prepares a protective interface that prevents damage to the organic light emitting layer during the subsequent metal deposition process, allowing the system to achieve both low sheet resistance and layer integrity
2Reliability
If the thickness of the upper electrode is increased to reduce sheet resistance, then electrical conductivity is improved, but light transmissivity deteriorates
Solution Approach 1:
The invention changes the parameters of the upper electrode system by introducing an organic buffer layer with specific thickness (50-200 Å) and composition characteristics. This allows the metal cathode to be deposited at optimized thickness to achieve low sheet resistance while the buffer layer parameters ensure sufficient light transmissivity is maintained
3Illumination intensity
If a metal thin film is formed to pass visible light, then transmissivity is improved, but sheet resistance increases
Solution Approach 1:
The upper electrode is constructed as a composite structure consisting of an organic buffer layer and a metal cathode layer. The buffer layer provides optical transparency while the metal layer provides electrical conductivity, creating a composite system that achieves both low sheet resistance and high light transmissivity simultaneously
4Reliability
If sputtering method is used to deposit TCO-based substance on metal thin film to reduce sheet resistance, then electrical conductivity is improved, but the organic light emitting layer is degraded or damaged
Solution Approach 1:
The organic buffer layer serves as a protective intermediary between the sputtering process and the organic light emitting layer. During TCO deposition by sputtering, the buffer layer absorbs the physical impacts and prevents degradation of the underlying organic light emitting layer, allowing the TCO layer to be formed for reducing sheet resistance
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 approach reduces sheet resistance, maintains high transmissivity, and enhances luminance efficiency by preventing damage to the organic light emitting layer and minimizing micro-cavity effects, resulting in improved display performance.
Implementation Method 1
a metal doped layer which reduces sheet resistance
Implementation Method 2
a charge injection layer formed by chemical vapor deposition to minimize physical impacts
Implementation Method 3
Such substance can be deposited only by using a sputtering method, which is one type of physical vapor deposition (PVD) method. In the sputtering method, cationized molecules (of a target) strike a deposition surface and they may degenerate or damage an already deposited organic light emitting layer
Data Source
AI summary
An organic light emitting display element includes a substrate, a lower electrode positioned on the substrate, at least one organic light emitting layer positioned on the lower electrode, a metal doped layer positioned on the organic light emitting layer, and an upper electrode positioned on the metal doped layer that includes a conductive material, and is configured to transmit light. Such organic light emitting display element is capable of minimizing degeneration and damage to the organic light emitting layer caused by sputtering.