Symmetric OLED Emissive Stack for Stable Multicolor Output

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Solution Overview

Problem

Existing OLED devices with multiple emissive layers suffer from color instability under varying driving conditions, particularly in full color displays where saturated red, green, and blue pixels are required.

Innovation Solution

The OLED device incorporates a first emissive stack with at least three emissive layers, where the layers nearest the electrodes emit the same color and intermediate layers emit different colors, with specific emission peak differences and dopant compositions to maintain color stability across varying current densities and luminance levels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If multiple emissive layers are used in OLED devices to achieve full color display, then color saturation and display quality are improved, but color stability deteriorates under varying driving conditions

Engineering Contradiction:

Improvecolor saturationVSAvoidcolor stability

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The emissive layer is divided into multiple segments (first emissive layer, second emissive layer, third emissive layer) with different color characteristics. The first and third layers emit the same color while the second layer emits a different color, creating a segmented structure that maintains color stability while achieving full color display capability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the emissive stack have different local properties - the first and third emissive layers are designed with specific color emission characteristics while the second emissive layer has different color emission. This local differentiation allows the overall device to maintain color stability while providing full color display.

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If emissive layers with different colors are stacked to achieve full color display, then display color range is improved, but color consistency across driving conditions deteriorates

Engineering Contradiction:

Improvedisplay color rangeVSAvoidcolor consistency

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The emissive stack is segmented into multiple layers with specific color characteristics. By having the first and third layers emit the same color while the second layer emits a different color, the device achieves both broad color range and consistent color reproduction across driving conditions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The symmetric structure with matching first and third emissive layers creates a self-balancing system that provides feedback compensation. When driving conditions change, the symmetric configuration ensures that color shifts in one region are compensated by opposite shifts in the other region, maintaining overall color consistency.

Inventive Principle:

Principle #23Feedback

3Device complexity

If simple emissive layer structures are used, then device complexity is reduced, but color stability under varying current densities deteriorates

Engineering Contradiction:

Improveemissive layer structureVSAvoidcolor stability

Core Design Contradiction:

Device complexityVSStability of the object's composition

Solution Approach 1:

The emissive layer is segmented into three distinct layers with specific color properties. This segmentation, while increasing structural complexity, provides the color stability needed for reliable operation across varying current densities by distributing the emission characteristics across multiple layers.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The device uses a composite emissive structure combining multiple emissive layers with different color characteristics. This composite approach, while more complex than a single layer, achieves superior color stability and reliability under varying operating conditions.

Inventive Principle:

Principle #40Composite materials

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

The solution ensures minimal color variation (Δuv < 0.02) in CIE (x, y) coordinates, maintaining color stability even at high current densities and luminance changes, enhancing the performance of full color displays.

Implementation Method 1

OLEDs make use of thin organic films that emit light when voltage is applied across the device

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Implementation Method 2

One application for phosphorescent emissive molecules is a full color display

Methodology Applied

Scientific EffectPhosphorescence: Phosphorescence

Data Source

PatentUS12588382B2Color stable multicolor OLED device structures

Publication Date: 2026.03.24 UNIVERSAL DISPLAY CORP

AI summary

The present invention relates to OLED devices and stacks for OLED devices that include a symmetric emissive-layer architecture. In one embodiment, the present invention relates to an emissive stack having three layers, wherein the top and bottom layers emit light in the same or similar color region while the middle layer emits light in a different color region than the other two layers. In such an embodiment, the three layers are in contact with each other with no other layers in between. The symmetric emissive-layer architecture of the present invention can be used to improve the color stability of OLED devices.