Dual Triplet-Acceptor OLED Emitter Composition

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Solution Overview

Problem

Organic light-emitting diodes (OLEDs) face performance issues due to triplet excitons, which can lead to non-radiative decay and reduced quantum efficiency, and existing solutions like perylene derivatives or triplet-quenching materials either improve lifetime but shift the emission spectrum or have limited efficiency.

Innovation Solution

A composition comprising a light-emitting material blended with two different triplet-accepting materials that reduce triplet exciton population through quenching or triplet-triplet annihilation, maintaining the emission spectrum and enhancing efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If a single triplet-accepting material is used to reduce triplet exciton population, then device lifetime is improved, but emission spectrum shifts significantly

Engineering Contradiction:

Improvedevice lifetimeVSAvoidemission spectrum

Core Design Contradiction:

Duration of action of stationary objectVSIllumination intensity

Solution Approach 1:

The patent divides the triplet-accepting function into two separate materials with different triplet energy levels. The first triplet-accepting material (with higher triplet energy) handles high-energy triplet excitons without causing significant emission spectrum shifts, while the second triplet-accepting material (with lower triplet energy) handles remaining triplet excitons. This segmentation allows the device to benefit from triplet quenching while maintaining emission spectrum stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Each triplet-accepting material is assigned a specific energy level range it handles, creating localized functionality within the light-emitting layer. The first triplet-accepting material operates in the higher energy regime, while the second operates in the lower energy regime, allowing each to optimize its performance for its specific energy range without interfering with the overall emission spectrum.

Inventive Principle:

Principle #3Local quality

2Duration of action of stationary object

If higher concentrations of triplet-accepting material are used to improve device lifetime, then lifetime increases, but emission spectrum red-shifts

Engineering Contradiction:

Improvedevice lifetimeVSAvoidemission spectrum

Core Design Contradiction:

Duration of action of stationary objectVSIllumination intensity

Solution Approach 1:

Instead of using high concentrations of a single triplet-accepting material, the patent segments the triplet-accepting function across two materials at optimized concentrations. This allows each material to work at lower, more effective concentrations, reducing the overall impact on emission spectrum while maintaining triplet quenching efficiency and device lifetime improvement.

Inventive Principle:

Principle #1Segmentation

3Reliability

If triplet-quenching materials are used to prevent triplet-triplet or triplet-singlet interactions, then device stability is improved, but quantum efficiency remains limited

Engineering Contradiction:

Improvedevice stabilityVSAvoidquantum efficiency

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent changes the energy level parameters of the triplet-accepting materials to optimize both stability and efficiency. By carefully selecting triplet energy levels that are lower than the light-emitting material but higher than the singlet energy level, the system prevents triplet-triplet and triplet-singlet interactions (improving stability) while allowing efficient energy transfer back to the singlet state for light emission (improving quantum efficiency).

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 use of two triplet-accepting materials in the light-emitting layer of OLEDs effectively reduces triplet exciton population, improving device lifetime and quantum efficiency while maintaining the emission spectrum, outperforming single triplet-accepting material approaches.

Implementation Method 1

a first triplet-accepting material and a second triplet-accepting material that is different from the first triplet-accepting material... which reduce triplet exciton population through quenching or triplet-triplet annihilation

Methodology Applied

Scientific EffectTriplet quenching:

Implementation Method 2

reduce triplet exciton population through quenching or triplet-triplet annihilation

Methodology Applied

Scientific EffectTriplet-triplet annihilation:

Implementation Method 3

These materials electroluminesce by radiative decay of singlet excitons (fluorescence)

Methodology Applied

Scientific EffectFluorescence: Fluorescence

Implementation Method 4

These materials electroluminesce by radiative decay of singlet excitons

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS10205114B2Organic light-emitting compositions having multiple triplet-accepting materials, and devices and methods thereof

Publication Date: 2019.02.12 CAMBRIDGE DISPLAY TECH LTD

AI summary

A composition suitable for use in an organic light-emitting layer (103) of an organic light-emitting device having an anode (101) and a cathode (105), the composition comprising a fluorescent light-emitting material, a first triplet-accepting material and a second triplet-accepting material that is different from the first triplet-accepting material. The fluorescent light-emitting material may be a repeat unit of a light-emitting polymer, and the first and second triplet-accepting materials may independently be repeat units of the light-emitting polymer or may be mixed with the fluorescent light-emitting material.