OLED Second Electrode Dipole Layer Design
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Solution Overview
Problem
Existing organic light-emitting display apparatuses face challenges in achieving efficient electron injection and low driving voltages due to high sheet resistance and aggregation issues with traditional electrode materials, which affect the external quantum efficiency and light emission.
Innovation Solution
The use of a second electrode structure comprising a dipole material layer, a low work function metal or metal oxide layer, and a conductive layer, with specific thickness ranges and materials like lithium fluoride (LiF), ytterbium (Yb), and silver (Ag), to improve electron injection and reduce sheet resistance, including an additional layer of Yb and Ag compound between the second and third layers to enhance uniformity and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional electrode materials are used, then the device structure is simple, but the sheet resistance is high and electron injection is inefficient
Solution Approach 1:
The second electrode is divided into multiple functional layers: a dipole material layer (first layer), a low work function layer (second layer), and a conductive material layer (third layer). This segmentation allows each layer to perform its specific function - the dipole layer improves electron injection, the low work function layer reduces injection barrier, and the conductive layer provides low sheet resistance - thereby resolving the contradiction between injection efficiency and structural simplicity.
Solution Approach 2:
The patent employs composite material structure in the second electrode by combining dipole materials (such as lithium fluoride), low work function materials (such as ytterbium), and conductive materials (such as silver). This composite approach achieves both high electron injection efficiency and low sheet resistance, overcoming the limitations of single-material electrodes while maintaining reasonable structural complexity.
2Power
If traditional electrode materials are used, then the manufacturing process is simple, but the driving voltage is high
Solution Approach 1:
The patent changes the physical and chemical parameters of the electrode materials by selecting dipole materials with specific dipole moments, low work function materials with work functions of 3.6 eV or less, and conductive materials with appropriate conductivity. These parameter optimizations enable low driving voltage operation while the thin film deposition processes maintain manufacturing feasibility.
Solution Approach 2:
The dipole material layer acts as an intermediary between the organic emission layer and the conductive material layer. It mediates the electron injection process by creating favorable electronic states at the interface, thereby reducing the driving voltage required for operation while the overall layered structure remains manufacturable through standard vacuum deposition techniques.
3Reliability
If traditional electrode materials are used, then the device is simple, but the external quantum efficiency is low
Solution Approach 1:
The second electrode is segmented into three functional layers with distinct roles: the dipole material layer (first layer, 0.5-5 nm thick) enhances electron injection by creating favorable interface states, the low work function layer (second layer, 0.5-5 nm thick) reduces the injection barrier, and the conductive layer (third layer, 0.5-5 nm thick) provides low sheet resistance. This segmentation achieves high external quantum efficiency while keeping each layer thin to minimize overall complexity.
Solution Approach 2:
Each layer in the second electrode is designed with specific local properties: the dipole material layer provides localized dipole moments at the interface with the organic emission layer, the low work function layer provides localized electron reservoir states, and the conductive layer provides localized high conductivity. These localized quality enhancements collectively improve external quantum efficiency without requiring uniform complexity throughout the entire electrode structure.
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 properties, reduces driving voltages, and increases external quantum efficiency, as demonstrated by improved current efficiency and reduced sheet resistance values.
Implementation Method 1
a first layer including a dipole material
Implementation Method 2
a second layer including a material having a work function of 3.6 eV or less
Implementation Method 3
holes injected from the hole injection electrodes and electrons injected from the electron injection electrodes may combine in the organic emission layer and generate excitons. Light may be generated as the excitons drop from an excited state to a ground state
Implementation Method 4
a third layer including a conductive material
Data Source
AI summary
Provided is an organic light-emitting display apparatus that includes a substrate; a first electrode on the substrate; an intermediate layer on the first electrode and including an organic emission layer; and a second electrode that includes a first layer including a dipole material, a second layer including a material having a work function of 3.6 eV or less, and a third layer including a conductive material, wherein the first to third layers are sequentially disposed on the intermediate layer.