Multicolor Light-Emitting Element With Fewer Exciplex–Phosphorescence Layers

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Solution Overview

Problem

Existing multicolor light-emitting elements using fluorescence and phosphorescence require a large number of layers, which hinders practical application and results in inefficient emission due to quenching and energy transfer issues, particularly when using host materials with condensed aromatic ring skeletons.

Innovation Solution

A light-emitting element with a stacked-layer structure comprising a first light-emitting layer exhibiting exciplex fluorescence and a second light-emitting layer exhibiting phosphorescence, where the exciplex is formed from two organic compounds with closely aligned singlet and triplet excited levels, allowing efficient energy transfer and reduced layer complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a large number of layers are used in multicolor light-emitting elements to achieve different emission colors, then color variety is improved, but device complexity and manufacturing difficulty increase

Engineering Contradiction:

Improvecolor varietyVSAvoidlayer count

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent combines multiple light-emitting functions into a single integrated light-emitting layer by using a host material that can simultaneously support both fluorescent and phosphorescent dopants. This merging approach eliminates the need for separate layers for different emission mechanisms, thereby reducing device complexity while maintaining color variety.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The host material is designed to perform multiple functions: it serves as the matrix for both fluorescent and phosphorescent dopants, facilitates energy transfer to both types of dopants, and enables simultaneous operation of different emission mechanisms within a single layer. This multi-functionality reduces the overall layer count while achieving multicolor emission.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Stability of the object's composition

If host materials with condensed aromatic ring skeletons are used, then structural stability is improved, but energy transfer efficiency decreases due to quenching effects

Engineering Contradiction:

Improvestructural stabilityVSAvoidenergy transfer efficiency

Core Design Contradiction:

Stability of the object's compositionVSLoss of energy

Solution Approach 1:

The patent introduces deuterium atoms at specific positions within the aromatic ring structure of the host material. This local modification with deuterium reduces non-radiative decay pathways and quenching effects at critical locations, thereby improving energy transfer efficiency to dopants while preserving the overall structural stability of the host material.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the physical-chemical parameters of the host material by substituting hydrogen atoms with deuterium atoms. This isotopic substitution alters vibrational frequencies and reduces non-radiative decay rates, thereby improving energy transfer efficiency while maintaining structural stability. The deuterium substitution specifically targets parameters related to energy dissipation pathways.

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 solution enables high emission efficiency with reduced layer count, facilitating cost-effective manufacturing and extended lifetime by minimizing energy transfer losses and quenching, suitable for multicolor and white light emission.

Implementation Method 1

a first light-emitting layer exhibiting light emission from a first exciplex

Methodology Applied

Scientific EffectExciplex fluorescence: Fluorescence

Implementation Method 2

allowing efficient energy transfer

Methodology Applied

Scientific EffectEnergy transfer:

Implementation Method 3

a second light-emitting layer exhibiting phosphorescence

Methodology Applied

Scientific EffectPhosphorescence: Phosphorescence

Implementation Method 4

By recombination of the injected electrons and holes, the organic compound having a light-emitting property is put in an excited state to provide light emission

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS12439814B2Light-emitting element, light-emitting device, display device, electronic appliance, and lighting device

Publication Date: 2025.10.07 SEMICON ENERGY LAB CO LTD

AI summary

A multicolor light-emitting element using fluorescence and phosphorescence, which has a small number of manufacturing steps owing to a relatively small number of layers to be formed and is advantageous for practical application can be provided. In addition, a multicolor light-emitting element using fluorescence and phosphorescence, which has favorable emission efficiency is provided. A light-emitting element which includes a light-emitting layer having a stacked-layer structure of a first light-emitting layer exhibiting light emission from a first exciplex and a second light-emitting layer exhibiting phosphorescence is provided.