Organic Light-Emitting Display Functional Layer Leakage Control

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Solution Overview

Problem

In organic light-emitting display devices with a patterned light-emitting layer structure, current leakage through common layers can cause unintended light emission in adjacent pixels, leading to color mixture and reduced display quality, especially at low gray scale driving where turn-on voltage differences between pixels exacerbate this issue.

Innovation Solution

Incorporating a functional layer with a lower HOMO level than the patterned hole transporting layer in the light-emitting element with a lower turn-on voltage to suppress current leakage from the common layer, effectively reducing unwanted light emission from adjacent pixels by increasing the barrier for hole flow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a common layer is shared by multiple pixels to improve manufacturing efficiency and reduce device complexity, then current leakage occurs through the common layer causing color mixture between adjacent pixels

Engineering Contradiction:

Improvemanufacturing efficiencyVSAvoidcolor mixture

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The patent divides the common layer into multiple isolated regions, each corresponding to a specific pixel. This segmentation prevents current leakage from spreading to adjacent pixels while maintaining the manufacturing advantages of common layers, as each segmented region can still be formed using common deposition processes.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediate barrier layer between adjacent common layers that acts as a mediator to block current leakage. This barrier layer prevents the harmful current flow between pixels while allowing the common layers to maintain their shared structure for efficient manufacturing.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If the turn-on voltage of adjacent pixels is different to accommodate varying light-emitting layer characteristics, then current leakage through common layers is exacerbated at low gray scale driving

Engineering Contradiction:

Improvepixel characteristic matchingVSAvoiddisplay quality

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies different voltage threshold characteristics to different pixel regions by segmenting the common layer. Each segmented common layer region is optimized for its corresponding pixel's specific turn-on voltage requirements, allowing adjacent pixels with different light-emitting layer characteristics to operate reliably without cross-pixel current leakage.

Inventive Principle:

Principle #3Local quality

3Device complexity

If organic layers are formed with common structure using common mask to simplify manufacturing, then current leakage through the continuous common layer causes adjacent pixels to emit light unintentionally

Engineering Contradiction:

Improvelayer structure complexityVSAvoidunintended light emission

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

The patent segments the common layer into discrete regions corresponding to individual pixels, eliminating the continuous path that allows current leakage. This segmentation can be achieved through patterning processes that are compatible with existing manufacturing workflows, maintaining ease of fabrication while preventing unintended light emission from adjacent pixels.

Inventive Principle:

Principle #1Segmentation

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 solution minimizes color mixture between adjacent pixels by reducing current leakage, thereby enhancing the display quality and optical efficiency of the organic light-emitting display device.

Implementation Method 1

Methodology Applied

Scientific EffectHOMO level energy barrier:

Data Source

PatentUS9722207B2Organic light-emitting display device

Publication Date: 2017.08.01 LG DISPLAY CO LTD

AI summary

Provided is a display device, including two light-emitting elements having different turn-on voltages. Each of the light-emitting elements includes a patterned electrode, a common layer, a patterned light-emitting layer, and a common electrode. The light-emitting element with the lower turn-on voltage among the two light-emitting elements includes a functional layer which suppresses a hole from being leaked from the light-emitting layer with the higher turn-on voltage through the common layer when the light-emitting element with the higher turn-on voltage among the two light-emitting elements is driven at a low gray scale to move into the patterned light-emitting layer of the light-emitting element with the lower turn-on voltage. Therefore, the light emission of an undesired pixel due to the leakage current is reduced, thereby improving the display quality.