OLED Hole Transporting Layer Segmentation for White Balance Stability
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Solution Overview
Problem
Organic light emitting display devices experience color-coordinate shifts in white balance due to temperature changes, primarily caused by variations in the hole mobility of the hole transporting layer, leading to unwanted lateral currents between OLEDs.
Innovation Solution
The implementation of a layered structure with a third hole transporting layer having a lower mobility, accompanied by first and second hole transporting layers with higher mobilities, strategically positioned to minimize lateral current and maintain consistent white balance across temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common hole transporting layer is formed on the entire display area, then device complexity is reduced and manufacturing is simplified, but lateral current occurs between adjacent OLEDs causing color-coordinate shift
Solution Approach 1:
The common hole transporting layer is divided into multiple layers with different hole mobilities. The first hole transporting layer has high hole mobility to efficiently transport holes, while the second hole transporting layer has low hole mobility to block lateral current between adjacent OLEDs. This segmentation resolves the contradiction by maintaining manufacturing simplicity while preventing lateral current through functional differentiation of layers.
Solution Approach 2:
Different regions of the hole transporting layer structure are assigned different hole mobility characteristics. The first hole transporting layer positioned near the OLEDs provides high hole mobility for efficient charge transport, while the second hole transporting layer positioned between adjacent OLEDs provides low hole mobility to block lateral current. This local quality differentiation eliminates lateral current while maintaining overall structural simplicity.
2Speed
If the hole mobility of the hole transporting layer is increased, then hole transport efficiency is improved, but lateral current increases causing color-coordinate shift at high temperature
Solution Approach 1:
The hole transporting layer is segmented into two distinct layers with different hole mobility values. The first hole transporting layer has high hole mobility to ensure efficient hole transport to the OLEDs, while the second hole transporting layer has low hole mobility to prevent lateral current between adjacent OLEDs. This segmentation allows simultaneous optimization of hole transport speed and lateral current blocking.
Solution Approach 2:
Different hole mobility characteristics are assigned to different positions within the hole transporting layer structure. The first hole transporting layer positioned adjacent to OLEDs provides high hole mobility for efficient charge injection, while the second hole transporting layer positioned between OLEDs provides low hole mobility to block lateral current. This local quality differentiation resolves the contradiction between transport efficiency and lateral current suppression.
3Reliability
If a low hole mobility layer is added to block lateral current, then white balance stability is improved, but device complexity and layer structure become more complex
Solution Approach 1:
The hole transporting layer is segmented into two functional layers: a first hole transporting layer with high hole mobility for efficient charge transport and a second hole transporting layer with low hole mobility for lateral current blocking. This segmentation achieves white balance stability while maintaining a relatively simple layered structure that can be integrated into existing OLED architectures.
Solution Approach 2:
The multi-layer hole transporting structure serves multiple functions simultaneously: the first layer provides efficient hole transport to OLEDs, the second layer blocks lateral current between adjacent OLEDs, and together they maintain stable white balance across temperature variations. This multi-functionality justifies the added structural complexity by delivering multiple performance benefits from a single integrated design.
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 reduces the color-coordinate difference of white light balance, ensuring stable image quality regardless of temperature changes by controlling hole mobility and minimizing lateral current variations.
Implementation Method 1
the amount of lateral current is in proportion to a hole mobility (m2V−1s−1) of the hole transporting layer
Implementation Method 2
a lateral current phenomenon may occur... an unwanted current is supplied from one OLED to another adjacent OLED
Data Source
AI summary
An organic light emitting display device according to an embodiment includes: a first anode electrode, a second anode electrode, and a third anode electrode, each anode electrode being spaced apart from each other; a bank disposed on edges of the first to third anode electrodes; a third hole transporting layer disposed on the first to third anode electrodes and the bank, and having a third hole mobility; a first hole transporting layer disposed on the third hole transporting layer and having a first hole mobility higher than the third hole mobility; and a second hole transporting layer disposed next to the first hole transporting layer on the third hole transporting layer and having a second hole mobility higher than the third hole mobility.