Organic Light-Emitting Display Device With High Refractive Index Auxiliary Layer
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Solution Overview
Problem
Organic light-emitting display devices face challenges in maintaining optical properties and reducing wiring resistance due to the damage of electrodes during the manufacturing process, particularly in large-sized panels, where the use of materials with low refractive indices for auxiliary layers can degrade light extraction efficiency.
Innovation Solution
The implementation of a second auxiliary layer with a higher refractive index, formed on the second electrode and covering the first auxiliary layer, along with a third electrode that is thicker than the second electrode to reduce surface resistance, and a first auxiliary layer with specific materials like 8-quinolinolato lithium and 2-(4-(9,10-di(naphthalene-2-yl)anthracene-2-yl)phenyl)-1-phenyl-1H-benzo-[D]imidazole, which facilitates patterning without additional processing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a first auxiliary layer with low refractive index material is used to protect the second electrode, then the second electrode is protected from damage, but light extraction efficiency deteriorates
Solution Approach 1:
The auxiliary layer is divided into two distinct segments: a first auxiliary layer (EP1) made of low refractive index material for electrode protection, and a second auxiliary layer (EP2) made of high refractive index material for light extraction enhancement. This segmentation allows each layer to fulfill its specific function without compromising the other, resolving the contradiction between protection and optical performance.
Solution Approach 2:
The auxiliary layer structure combines two materials with different refractive index properties - a low refractive index material (e.g., Liq, TCTA) for protection and a high refractive index material (e.g., N4,N4′-diphenyl-N4,N4′-bis(9-phenyl-9H-carbazol-3-yl)diphenyl-4,4′-diamine) for light extraction. This composite structure enables simultaneous achievement of protective and optical enhancement functions.
2Ease of manufacture
If the second electrode is made thinner to reduce manufacturing complexity, then manufacturing becomes easier, but surface resistance increases causing voltage drop
Solution Approach 1:
The third electrode (EP3) is selectively formed only in the non-emission region where electrical connection is needed, with a greater thickness than in the emission region. This local quality enhancement provides low resistance electrical connection without interfering with light emission in the pixel area, resolving the contradiction between ease of manufacture and energy loss.
3Loss of energy
If the third electrode is formed with greater thickness to reduce surface resistance, then voltage drop is reduced, but device complexity increases
Solution Approach 1:
The third electrode (EP3) is formed in advance during the manufacturing process with a greater thickness in the non-emission region before final device assembly. This preliminary action ensures low resistance electrical connection is established early, avoiding the need for additional complex structures or post-processing steps to reduce voltage drop.
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 optical properties by improving light extraction efficiency and reduces voltage drop, while also allowing for the natural patterning of the third electrode without separate processing, thus protecting the second electrode and maintaining the integrity of the display device.
Implementation Method 1
a second auxiliary layer that is stacked on at least the first auxiliary layer and has a refractive index higher than that of the first auxiliary layer
Data Source
AI summary
An organic light-emitting display device includes a thin film transistor, a first insulating layer, a first electrode a second insulating layer, an organic emission layer, a second electrode, a first auxiliary layer in a first region on the second electrode and having a first edge, a third electrode in a second region, on the second electrode and having a second edge contacting the first edge of the first auxiliary layer, and a second auxiliary layer on at least the first region and having a refractive index higher than the first auxiliary layer.