Nitrogen-Containing TADF Compound for OLED Emission Efficiency

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Solution Overview

Problem

Current organic electroluminescence devices face challenges in reducing driving voltage and increasing emission efficiency and lifetime, with existing materials not effectively utilizing delayed fluorescence phenomena for improved performance.

Innovation Solution

A nitrogen-containing compound with a specific molecular structure, represented by Formula 1, is used as a thermally activated delayed fluorescence material in the emission layer of an organic electroluminescence device, featuring a small energy difference between singlet and triplet excitation levels to enhance emission efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional organic electroluminescence materials are used, then the device structure is simple, but the emission efficiency is low and triplet state energy is not effectively utilized

Engineering Contradiction:

Improveemission efficiencyVSAvoidtriplet state energy loss

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The patent modifies the molecular structure parameters of the organic compound by introducing specific nitrogen-containing groups (pyridine, pyrimidine, triazine rings) and adjusting HOMO-LUMO energy levels to enable TADF emission. This changes the energy transition parameters to allow efficient triplet-to-singlet conversion, directly improving emission efficiency while utilizing previously wasted triplet state energy.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates composite emission layers by combining TADF emitters with host materials having complementary energy levels. The host-guest system forms a composite structure where the host provides structural stability and energy transfer, while the TADF emitter provides efficient luminescence, achieving both high emission efficiency and effective triplet energy utilization.

Inventive Principle:

Principle #40Composite materials

2Productivity

If phosphorescence emission using triplet state energy is used, then emission efficiency can be improved, but the device complexity and material stability requirements increase

Engineering Contradiction:

Improveemission efficiencyVSAvoidmaterial structure complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent replaces the heavy metal-based phosphorescence mechanism (requiring Ir, Pt complexes) with a purely organic TADF mechanism based on singlet-triplet energy gap manipulation. This substitution eliminates the need for complex coordination chemistry and heavy metals, simplifying material structure while maintaining high emission efficiency through thermal activation of delayed fluorescence.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Use of energy by stationary object

If driving voltage is reduced to improve device performance, then energy consumption decreases, but emission efficiency and lifetime may be compromised

Engineering Contradiction:

Improveenergy consumptionVSAvoidemission efficiency

Core Design Contradiction:

Use of energy by stationary objectVSProductivity

Solution Approach 1:

The patent optimizes the HOMO-LUMO energy gap and singlet-triplet energy difference parameters to achieve low driving voltage operation. By carefully tuning these energy parameters, the device can operate at reduced voltages while maintaining high emission efficiency through efficient charge injection and balanced electron-hole recombination enabled by the TADF mechanism.

Inventive Principle:

Principle #35Parameter changes

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 nitrogen-containing compound improves the emission efficiency of organic electroluminescence devices by facilitating thermally activated delayed fluorescence, leading to higher external quantum efficiency and stable performance.

Implementation Method 1

a strategy utilizing delayed fluorescence phenomenon via a thermally activated delayed fluorescence (TADF) material is also being developed

Methodology Applied

Scientific EffectThermally activated delayed fluorescence: Phosphorescence

Implementation Method 2

delayed fluorescence emission using the phenomenon of producing singlet excitons by the collision of triplet excitons (triplet-triplet annihilation, TTA)

Methodology Applied

Scientific EffectTriplet-triplet annihilation:

Data Source

PatentUS10930858B2Nitrogen-containing compound and organic electroluminescence device including the same

Publication Date: 2021.02.23 SAMSUNG DISPLAY CO LTD

AI summary

A nitrogen-containing compound which improves emission efficiency, and an organic electroluminescence device including the same are provided. The nitrogen-containing compound according to the present disclosure is represented by Formula 1:When the nitrogen-containing compound has an appropriate or suitable cyclic molecular structure, a small ΔEST value may be obtained, and an organic electroluminescence device including the nitrogen-containing compound in the emission layer may exhibit thermally activated delayed fluorescence emission and have improved external quantum efficiency.