OLED Emissive Layer FRET Energy Transfer

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Solution Overview

Problem

Current organic light emitting diodes (OLEDs) face challenges in achieving high luminous efficiency and long luminous lifespan, with fluorescent materials showing low efficiency and phosphorescent materials having short lifespan due to the limited use of triplet excitons.

Innovation Solution

An OLED structure incorporating an emissive layer with a first compound that utilizes only singlet excitons and a second compound that uses both singlet and triplet excitons, where the second compound transfers exciton energy to the first compound via the Forster Resonance Energy Transfer (FRET) mechanism, enhancing luminous efficiency and lifespan.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If fluorescent material is used in OLED, then the device structure is simple, but luminous efficiency is low because only singlet excitons are utilized

Engineering Contradiction:

Improvedevice structureVSAvoidluminous efficiency

Core Design Contradiction:

Device complexityVSUse of energy by moving object

Solution Approach 1:

The patent combines fluorescent and phosphorescent materials in a single emissive layer to create a hybrid system. The phosphorescent material (iridium complex) utilizes triplet excitons while the fluorescent material utilizes singlet excitons, merging their advantages to achieve high luminous efficiency without requiring separate emission layers.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The emissive layer is formulated as a composite material containing both fluorescent compounds (e.g., BPhen, Bpy-OXD) and phosphorescent iridium complexes. This composite approach allows simultaneous exploitation of singlet and triplet excitons, achieving near 100% internal quantum efficiency while maintaining a single-layer structure.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If phosphorescent material is used in OLED, then luminous efficiency is high because both singlet and triplet excitons are utilized, but luminous lifespan is short

Engineering Contradiction:

Improveluminous efficiencyVSAvoidluminous lifespan

Core Design Contradiction:

Use of energy by moving objectVSDuration of action of stationary object

Solution Approach 1:

The fluorescent material acts as an intermediary that receives energy from the phosphorescent material through FRET and transfers it to generate fluorescence. This mediator approach allows the system to benefit from the high efficiency of phosphorescent triplet utilization while the fluorescent material provides longer operational stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent substitutes the direct phosphorescent emission mechanism with an indirect energy transfer mechanism where the phosphorescent material generates excitons that are then transferred to fluorescent emitters. This substitution replaces the short-lived phosphorescent emission with longer-lived fluorescent emission, extending device lifespan.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Use of energy by moving object

If phosphorescent material is used in OLED, then luminous efficiency is improved, but color purity deteriorates

Engineering Contradiction:

Improveluminous efficiencyVSAvoidcolor purity

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

The patent assigns different functional roles to different materials within the emissive layer: the phosphorescent iridium complex is optimized for high efficiency energy capture and transfer, while the fluorescent materials (BPhen, Bpy-OXD) are selected and positioned to provide specific color emission characteristics. This local optimization of material properties achieves both high efficiency and color purity.

Inventive Principle:

Principle #3Local quality

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 improves the luminous efficiency, luminous lifespan, and color purity of OLEDs by efficiently transferring exciton energy from the phosphorescent material to the fluorescent material, resulting in enhanced performance.

Implementation Method 1

the second compound transfers exciton energy to the first compound via the Forster Resonance Energy Transfer (FRET) mechanism

Methodology Applied

Scientific EffectForster Resonance Energy Transfer (FRET):

Data Source

PatentUS20240224790A1Organic light emitting diode

Publication Date: 2024.07.04 LG DISPLAY CO LTD

AI summary

An organic light emitting diode including a first electrode; a second electrode facing the first electrode; and an emissive layer disposed between the first electrode and the second electrode. The emissive layer includes at least one emitting material layer that includes a first compound including a first organic compound represented by Chemical Formula 1, and a second compound including an organometallic compound represented by Chemical Formula 4. The first organic compound may include multiple aromatic and heteroaromatic fused rings. The second compound may be a phosphorescent material. The first compound may have a wide plate-like structure and the first compound may receive efficiently exciton energy from the second compound. The present disclose also relates to an organic light emitting device including the diode. The luminous efficiency, luminous lifespan and color purity of the diode and device may be improved by introducing the first and second compounds into the emissive layer.