OLED Emissive Layer Combining Phosphorescent and Fluorescent Emitters

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Solution Overview

Problem

There is a deficit of efficient phosphorescent emissive materials that demonstrate long operational stability, particularly in the blue region, and fluorescent OLEDs face issues with triplet-triplet annihilation degrading device performance at high current densities.

Innovation Solution

Incorporating a phosphorescent emitter and a fluorescent emitter in the emissive layer, with energy transfer between them, primarily redistributing excited states to stable fluorescent emitters, using mechanisms like Dexter and Förster resonant energy transfer to enhance device operational stability and efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If phosphorescent emitters are used to harvest triplet excitons, then efficiency is improved, but operational stability deteriorates due to lack of efficient phosphorescent materials in blue region

Engineering Contradiction:

ImproveefficiencyVSAvoidoperational stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent introduces a fluorescent emitter as an intermediary between the electrogenerated excitons and the final light emission. The phosphorescent emitter harvests triplet excitons and transfers energy to the fluorescent emitter, which then emits light. This mediator approach allows the system to benefit from both phosphorescent exciton harvesting and fluorescent operational stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The emissive layer is designed as a composite system containing both phosphorescent and fluorescent emitters in a host matrix. This composite structure enables the system to combine the advantages of phosphorescent materials (triplet exciton harvesting) with the advantages of fluorescent materials (operational stability and resistance to triplet-triplet annihilation).

Inventive Principle:

Principle #40Composite materials

2Reliability

If fluorescent emitters are used for emission, then operational stability is improved, but efficiency deteriorates due to waste of triplet excitons

Engineering Contradiction:

Improveoperational stabilityVSAvoidefficiency

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The phosphorescent emitter serves as an intermediary that captures the otherwise wasted triplet excitons and transfers their energy to the fluorescent emitter. This allows the fluorescent emitter to maintain its operational stability while the phosphorescent emitter ensures efficient utilization of all excitons (both singlet and triplet).

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If high current densities are applied, then productivity is improved, but harmful factors increase due to triplet-triplet annihilation

Engineering Contradiction:

Improvecurrent densityVSAvoidtriplet-triplet annihilation

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the potentially harmful triplet excitons that would otherwise undergo annihilation into useful energy transfer to the fluorescent emitter. By introducing the phosphorescent emitter, the system transforms the harmful triplet-triplet annihilation pathway into a beneficial energy transfer pathway that enhances overall efficiency.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 approach maintains high efficiency while improving operational stability by utilizing electrogenerated excitons efficiently and avoiding triplet-triplet annihilation, enhancing the color quality and stability of OLEDs.

Implementation Method 1

using mechanisms like Dexter and Förster resonant energy transfer to enhance device operational stability and efficiency

Methodology Applied

Scientific EffectDexter energy transfer:

Implementation Method 2

using mechanisms like Dexter and Förster resonant energy transfer to enhance device operational stability and efficiency

Methodology Applied

Scientific EffectFörster resonant energy transfer:

Implementation Method 3

The phosphorescent emitter harvests electrogenerated excitons and transfers energy to the fluorescent emitter

Methodology Applied

Scientific EffectPhosphorescence: Phosphorescence

Implementation Method 4

the fluorescent emitter, with energy transfer between them, primarily redistributing excited states to stable fluorescent emitters

Methodology Applied

Scientific EffectFluorescence: Fluorescence

Implementation Method 5

OLEDs are typically multilayer devices which upon an applied voltage are capable emitting light from the radiative relaxation of an excited state located on an organic material

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS20260062608A1Organic light-emitting diodes with fluorescent and phosphorescent emitters

Publication Date: 2026.03.05 ARIZONA BOARD OF REGENTS ON BEHALF OF ARIZONA UNIV

AI summary

A light emitting device includes a first electrode, a hole transporting layer in contact with the first electrode, a second electrode, an electron transporting layer in contact with the second electrode; and an emissive layer between the hole transporting layer and the electron transporting layer. The emissive layer includes a phosphorescent emitter, a fluorescent emitter, and a host, and the phosphorescent emitter harvests electrogenerated excitons and transfers energy to the fluorescent emitter.