OLED TADF Dopant Blocking Layer Interface Emission

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Solution Overview

Problem

Organic light-emitting devices face inefficiencies in light emission due to triplet exciton concentration and movement to non-emissive regions, leading to reduced efficiency and lifespan.

Innovation Solution

Incorporating a thermally activated delayed fluorescence (TADF) emission dopant in an organic light-emitting device with a host and blocking materials that satisfy specific energy level conditions, where the blocking material's triplet energy level is higher than the dopant and host, to enhance light emission at interfaces and reduce triplet exciton concentration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If carriers recombine in the emission layer to produce excitons, then light emission occurs, but triplet excitons move to non-emissive regions reducing efficiency

Engineering Contradiction:

Improvetriplet exciton lossVSAvoidlight emission efficiency

Core Design Contradiction:

Loss of energyVSProductivity

Solution Approach 1:

The patent converts harmful triplet exciton movement to non-emissive regions into a beneficial interface emission mechanism. By designing the emission layer to directly contact blocking layers and utilizing energy level differences (T1(BL) > T1(D) > T1(H)), triplet excitons that would normally be lost are instead confined to emit light at the emission layer/blocking layer interfaces, transforming energy loss into useful light output.

Inventive Principle:

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

Solution Approach 2:

The patent creates localized emission regions at the interfaces between the emission layer and blocking layers. The emission characteristics are made non-uniform, with enhanced emission specifically at the interface regions where energy level gradients exist, rather than uniform emission throughout the entire emission layer. This local quality enhancement concentrates light emission where it is most efficient.

Inventive Principle:

Principle #3Local quality

2Quantity of substance

If triplet excitons move to non-emissive regions, then exciton concentration increases there, but light emission efficiency decreases

Engineering Contradiction:

Improveexciton concentrationVSAvoidlight emission efficiency

Core Design Contradiction:

Quantity of substanceVSProductivity

Solution Approach 1:

The patent transforms the harmful accumulation of triplet excitons in non-emissive regions into a beneficial phenomenon by designing interface regions where these excitons can emit light. The blocking layers prevent exciton migration to truly non-emissive regions, and the energy level structure (T1(BL) > T1(D) > T1(H)) ensures that excitons confined at interfaces produce useful emission rather than being lost.

Inventive Principle:

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

3Productivity

If the emission layer contacts blocking layers directly, then interface emission is enhanced, but device structure complexity increases

Engineering Contradiction:

Improveinterface emission efficiencyVSAvoidlayer structure complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent merges the emission layer and blocking layer into direct contact, eliminating intermediate layers that would otherwise be present in conventional OLED structures. This merging reduces the total number of layers and simplifies the device structure while simultaneously creating the desired interface emission effect. The blocking layers serve dual functions: blocking carrier injection and enabling interface emission.

Inventive Principle:

Principle #5Merging (Combining)

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 increases light emission efficiency by trapping excitons within the emission layer, improving device efficiency and lifespan by blocking exciton movement to non-emissive regions and enhancing TADF characteristics at interfaces.

Implementation Method 1

an emission layer between the first electrode and the second electrode; and at least one of an electron blocking layer between the first electrode and the emission layer and directly contacting the emission layer, and a hole blocking layer between the second electrode and the emission layer and directly contacting the emission layer. The emission layer includes a host and a dopant, and the dopant emits delayed fluorescence or fluorescence

Methodology Applied

Scientific EffectThermally activated delayed fluorescence (TADF):

Implementation Method 2

the host, the dopant, and the blocking material satisfy Equation 1 below: T1(BL)>T1(D)>T1(H), where T1(BL) is a lowest excitation triplet energy level of the blocking material, T1(D) is a lowest excitation triplet energy level of the dopant, and T1(H) is a lowest excitation triplet energy level of the host

Methodology Applied

Scientific EffectEnergy level barrier effect:

Data Source

PatentUS11417865B2Organic light-emitting device

Publication Date: 2022.08.16 SAMSUNG DISPLAY CO LTD

AI summary

An organic light-emitting device including an emission layer that is adjacent to a hole blocking layer or an electron blocking layer and includes a thermally activated delayed fluorescence (TADF) emission dopant.