Organic EL Display Electron Transport Layer Quenching
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Solution Overview
Problem
Existing organic EL display devices face issues with low emission efficiency and short life due to insufficient electron injection into the emitting layers, primarily because the direct contact between the emitting layer and the cathode electrode leads to quenching, and the use of a single electron injecting material for all colors results in uneven efficiency and life characteristics.
Innovation Solution
The organic EL display device incorporates a substrate with lower electrodes, hole injecting/transporting layers, organic light emitting layers containing low-molecular weight materials, an electron injecting/transporting layer covering the entire surface, and an upper electrode, formed using a coating method and vapor deposition, allowing for efficient electron injection and improved carrier balance across different colors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the emitting layer is made thick to avoid quenching from direct contact with the cathode electrode, then quenching is reduced, but the drive voltage increases
Solution Approach 1:
An electron transporting layer made of low-molecular weight material is introduced as an intermediary between the cathode electrode and the emitting layer. This layer facilitates electron injection while preventing direct contact between the cathode and emitting layer, thus avoiding quenching without requiring excessive thickness that would increase drive voltage.
2Device complexity
If a single electron injecting material is used for all colors, then device structure is simplified, but emission efficiency and life uniformity across colors deteriorates
Solution Approach 1:
The patent introduces color-specific electron transporting layers with different materials optimized for each color (red, green, blue). Each layer has locally optimized properties to match the specific emitting layer requirements, achieving uniform emission efficiency and life across all colors while maintaining a unified overall structure.
3Area of stationary object
If coating method is used instead of vacuum vapor deposition, then large-sized panel production becomes feasible, but material dissolution and solvent removal steps are required
Solution Approach 1:
The patent employs coating methods with carefully controlled solvent selection and drying parameters. By optimizing solvent choice and drying conditions, the process achieves uniform film formation on large substrates without requiring excessive process steps, making large-panel production feasible while managing process complexity.
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 electron injection efficiency, leading to improved emission efficiency and extended life of the organic EL display device while reducing the drive voltage, and allows for the production of large-sized panels with uniform color performance.
Implementation Method 1
the organic EL display device emitting light based on the principle of organic electroluminescence
Implementation Method 2
efficient electron injection into the organic light emitting layers from the upper electrode
Data Source
AI summary
Disclosed herein is an organic electroluminescence display device including: a substrate; a plurality of lower electrodes formed thereon for each of a plurality of organic electroluminescence elements; a plurality of hole injecting/transporting layers capable of either hole injection or hole transportation which are formed on the lower electrodes for each of the organic electroluminescence elements; a plurality of organic light emitting layers containing a low-molecular weight material which are formed on the hole injecting/transporting layers for each of the organic electroluminescence elements; an electron injecting/transporting layer capable of either electron injection or electron transportation which is formed over the entire surface of the organic light emitting layers; and an upper electrode formed on the electron injecting/transporting layer.