OLED Second Electrode Alloy Layering for Viewing Angle Stability
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Solution Overview
Problem
Organic light emitting diode displays face issues with reduced light emission efficiency and color changes when viewed from different angles due to inner reflection and destructive interference, and existing structures that enhance light emission efficiency can lead to oxidation and reduced reliability of electrodes.
Innovation Solution
The use of a second electrode with a bottom region of MgAg alloy and a top region of AgMg alloy, along with an electron transport layer and auxiliary layers, helps maintain light emission efficiency across viewing angles while reducing oxidation and enhancing the electrode's resistance to oxidation, thereby increasing the reliability of the organic light emitting diode and display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the structure of the organic light emitting diode is changed to increase light emission efficiency, then light emission efficiency is improved, but color change depending on viewing angle is generated
Solution Approach 1:
The second electrode is divided into multiple layers with different compositions and thicknesses. The first layer contains Mg with 1-10 nm thickness, the second layer contains Ag with 10-30 nm thickness, and the third layer contains Mg with 30-70 nm thickness. This segmented structure allows each layer to contribute differently to light extraction while maintaining color consistency across viewing angles.
Solution Approach 2:
Different regions of the electrode structure are assigned different material compositions and thicknesses to optimize specific functions. The Mg-rich first and third layers provide light extraction enhancement, while the Ag-rich second layer provides structural stability and oxidation resistance. This local differentiation resolves the contradiction between efficiency enhancement and color stability.
2Ease of manufacture
If a single layer structure is used for the second electrode, then manufacturing is simplified, but oxidation resistance and reliability are reduced
Solution Approach 1:
The second electrode uses a composite structure with three layers containing different metal compositions (Mg-rich, Ag-rich, Mg-rich). This composite approach combines the advantages of each material: Mg provides good light extraction properties while Ag provides oxidation resistance. The multi-layer composite structure achieves superior reliability without significantly complicating the manufacturing process.
3Reliability
If the thickness of the second electrode is increased to improve oxidation resistance, then reliability is improved, but light transmittance is reduced
Solution Approach 1:
The total thickness of the second electrode is controlled within the range of 40-120 nm, with specific thickness ranges for each layer (first layer: 1-10 nm, second layer: 10-30 nm, third layer: 30-70 nm). By optimizing these parameters, the electrode achieves sufficient oxidation resistance while maintaining high light transmittance. The thinner Mg layers provide light extraction enhancement without excessive thickness that would block light.
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 maintains light emission efficiency and reduces color changes with viewing angles, while improving the structural reliability of the organic light emitting diode and display by minimizing oxidation of the electrode, thus enhancing overall performance.
Implementation Method 1
light reflected by the electrode and/or inner layers
Implementation Method 2
destructive interference of the light reflected by the electrode and/or inner layers
Implementation Method 3
electron transport layer disposed between the emission layer and the second electrode
Implementation Method 4
holes supplied from an anode and electrons supplied from a cathode may be combined in an organic emission layer to form an exciton. Light may be emitted while the exciton is stabilized
Data Source
AI summary
An organic light emitting diode according to the present disclosure includes a first electrode, a second electrode overlapping the first electrode, and an emission layer disposed between the first electrode and the second electrode. The second electrode includes a bottom region and a top region. The bottom region includes a MgAg alloy including more Mg than Ag. The top region includes a AgMg alloy including more Ag than Mg.