Phosphorescent Light-Emitting Layers for Balanced Multi-Dopant Emission

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Solution Overview

Problem

Current light-emitting elements using phosphorescent compounds face challenges in achieving high external quantum efficiency and balancing light emissions from multiple dopants with different emission colors, resulting in low efficiency and complex manufacturing processes.

Innovation Solution

A light-emitting element structure is developed with multiple phosphorescent layers, including a first and second light-emitting layer with specific carrier-transport compounds and host materials, where the triplet excitation energy of the host material is higher than that of the carrier-transport compounds, allowing for efficient energy transfer and balanced light emission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If multiple phosphorescent dopants with different emission colors are used in a single light-emitting layer, then the light emission balance is improved, but the manufacturing complexity increases

Engineering Contradiction:

Improvelight emission balanceVSAvoidmanufacturing complexity

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The patent divides the light-emitting element into multiple light-emitting layers, with each layer containing a specific phosphorescent dopant for a particular emission color (blue, green, red). This segmentation allows each layer to be optimized independently for its specific dopant, simplifying the manufacturing process compared to attempting to balance multiple dopants in a single layer.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from a single-layer structure to a multi-layer structure, adding the vertical dimension (number of layers) to achieve color balance. By stacking multiple light-emitting layers with different phosphorescent dopants, the patent achieves balanced light emission while maintaining manufacturing simplicity through standardized layer fabrication processes.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Use of energy by moving object

If phosphorescent compounds are used to achieve high internal quantum efficiency, then the emission efficiency is improved, but the external quantum efficiency remains low due to energy transfer losses

Engineering Contradiction:

Improveemission efficiencyVSAvoidenergy transfer losses

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

The patent assigns different host materials with specific triplet excitation energies to different light-emitting layers based on their respective phosphorescent dopants. Each layer is locally optimized with a host material whose triplet energy level is higher than that of the dopant, ensuring efficient energy transfer while minimizing losses. This local quality approach maximizes external quantum efficiency for each emission color.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If a single host material is used for multiple phosphorescent dopants, then the manufacturing process is simplified, but the energy transfer efficiency decreases due to mismatched triplet excitation energies

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoidenergy transfer efficiency

Core Design Contradiction:

Ease of manufactureVSUse of energy by moving object

Solution Approach 1:

The patent segments the light-emitting element into multiple layers, each with its own optimized host material-dopant combination. This segmentation allows each layer to achieve high energy transfer efficiency through matched triplet excitation energies, while the overall manufacturing process remains simplified through standardized multi-layer fabrication techniques.

Inventive Principle:

Principle #1Segmentation

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 enhances emission efficiency and reduces power consumption, providing a balanced and efficient light-emitting element suitable for display and lighting devices with simplified manufacturing.

Implementation Method 1

the triplet excitation energy of the host material is higher than that of the carrier-transport compounds, allowing for efficient energy transfer

Methodology Applied

Scientific EffectEnergy transfer:

Implementation Method 2

light emission from the triplet excited state (T*) is referred to as phosphorescence

Methodology Applied

Scientific EffectPhosphorescence: Phosphorescence

Data Source

PatentUS20240365578A1Light-Emitting Element, Light-Emitting Device, Display Device, Electronic Device, And Lighting Device

Publication Date: 2024.10.31 SEMICON ENERGY LAB CO LTD

AI summary

A light-emitting element which uses a plurality of kinds of light-emitting dopants emitting light in a balanced manner and has high emission efficiency is provided. Further, a light-emitting device, a display device, an electronic device, and a lighting device each having reduced power consumption by using the above light-emitting element are provided. A light-emitting element which includes a plurality of light-emitting layers including different phosphorescent materials is provided. In the light-emitting element, the light-emitting layer which includes a light-emitting material emitting light with a long wavelength includes two kinds of carrier-transport compounds having properties of transporting carriers with different polarities. Further, in the light-emitting element, the triplet excitation energy of a host material included in the light-emitting layer emitting light with a short wavelength is higher than the triplet excitation energy of at least one of the carrier-transport compounds.