Organic Light-Emitting Device With Cooling Dopant

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Solution Overview

Problem

Current organic light-emitting devices face challenges in extending lifespan due to triplet excitons remaining in an excited state, leading to reduced efficiency and chemical bond degradation, particularly in the emission layer where exciton-exciton annihilation and charge imbalance occur.

Innovation Solution

Incorporating a cooling dopant and sensitizer in the emission layer, where the sensitizer includes platinum (Pt) or is a thermally activated delayed fluorescence emitter, satisfying specific decay time conditions to rapidly convert triplet excitons to singlet excitons, thereby reducing hot excitons and enhancing lifespan.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If triplet excitons remain in excited state in the emission layer, then light emission occurs, but device lifespan is reduced and efficiency decreases

Engineering Contradiction:

Improvelight emissionVSAvoiddevice lifespan

Core Design Contradiction:

Illumination intensityVSDuration of action of stationary object

Solution Approach 1:

The patent introduces a cooling dopant as an intermediary substance in the emission layer that mediates the energy transfer from triplet excitons to singlet excitons. This cooling dopant acts as a bridge between the sensitizer (which generates triplet excitons) and the host material, enabling efficient energy conversion while preventing harmful triplet exciton accumulation that would otherwise degrade the device.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the energy level parameters of the emission layer by carefully selecting materials with specific energy levels. The cooling dopant is chosen to have energy levels that satisfy specific conditions (T1(H) < S1(CD) < T1(S)) to enable efficient energy transfer. By adjusting these energy level parameters, the system converts triplet excitons to singlet excitons, improving both efficiency and lifespan.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If triplet excitons accumulate in the emission layer, then exciton-exciton annihilation occurs, but chemical bond degradation accelerates

Engineering Contradiction:

Improveexciton densityVSAvoidchemical bond stability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent converts the harmful effect of triplet exciton accumulation into a beneficial process. Instead of allowing triplet excitons to cause degradation through accumulation, the cooling dopant transforms them into singlet excitons, which are less harmful. This converts the potentially damaging triplet state into a useful singlet state that can emit light without causing chemical bond degradation.

Inventive Principle:

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

Solution Approach 2:

The cooling dopant serves as an intermediary that facilitates the conversion of triplet excitons to singlet excitons. This intermediary substance absorbs the harmful triplet excitons and transforms them into beneficial singlet excitons, preventing direct damage to the chemical bonds in the emission layer while maintaining exciton density for light emission.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If conventional emission layers are used, then device structure is simple, but energy loss increases and efficiency decreases

Engineering Contradiction:

Improveemission layer structureVSAvoidenergy loss

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The patent employs a composite emission layer structure consisting of four components: host material, sensitizer, cooling dopant, and guest material. This composite structure enables multiple functions to be performed simultaneously: the sensitizer generates triplet excitons, the cooling dopant converts them to singlet excitons, and the guest material emits light. This multi-component composite approach reduces energy loss while maintaining manageable device complexity.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The emission layer is designed with multi-functionality where each component serves multiple purposes. The cooling dopant, for example, not only converts triplet to singlet excitons but also helps maintain energy balance in the system. The sensitizer both generates excitons and influences the energy distribution. This multi-functional design reduces overall energy loss without proportionally increasing device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 leads to improved efficiency and prolonged lifespan of organic light-emitting devices by minimizing energy loss and maintaining high color purity through efficient energy transfer and reduced triplet exciton accumulation.

Implementation Method 1

rapidly convert triplet excitons to singlet excitons, thereby reducing hot excitons and enhancing lifespan

Methodology Applied

Scientific EffectEnergy transfer:

Implementation Method 2

efficient energy transfer and reduced triplet exciton accumulation

Methodology Applied

Scientific EffectEnergy transfer:

Data Source

PatentEP3739645B1Organic light-emitting device

Publication Date: 2022.08.31 SAMSUNG ELECTRONICS CO LTD

Figure 1~2A
Figure 2B~2C
Figure 3~4

AI summary

Provided is an organic light-emitting device including a host, a cooling dopant, and a sensitizer.