Organic Electroluminescent Element with Stacked Fluorescent and Phosphorescent Units
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Solution Overview
Problem
Existing organic electroluminescent elements face challenges in achieving high color rendering properties and efficient light emission across various color temperatures without significant changes in materials or structure, particularly in multiunit configurations.
Innovation Solution
An organic electroluminescent element is designed with a first light-emitting unit using a blue fluorescent layer and a green fluorescent layer, and a second light-emitting unit using a red phosphorescent layer and a green phosphorescent layer, stacked with an intermediate layer, allowing for emission of white light across a range of color temperatures through the triplet-triplet fusion phenomenon, while maintaining high efficiency and long life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a multiunit structure with stacked light-emitting units is used to achieve various color temperatures, then color temperature adjustability is improved, but efficiency balance between units deteriorates
Solution Approach 1:
The patent adjusts the thickness parameters of individual light-emitting layers (first blue fluorescent layer: 5-20nm, first green fluorescent layer: 5-20nm, second green phosphorescent layer: 5-20nm, second red phosphorescent layer: 5-20nm) to optimize the efficiency balance between stacked units while maintaining color temperature adjustability. By controlling layer thickness, the invention achieves uniform efficiency across multiple units without requiring material changes.
2Illumination intensity
If light-emitting materials are changed to achieve various color temperatures, then color rendering properties are improved, but device complexity increases
Solution Approach 1:
The patent employs a universal host material (mCP - 4,7-diphenyl-1,10-phenanthroline) across all light-emitting layers that can accommodate different dopant materials (fluorescent and phosphorescent). This multi-functional host material enables color temperature adjustment through dopant selection while maintaining structural simplicity and manufacturing consistency.
Solution Approach 2:
The invention uses composite material systems combining host materials (mCP) with various dopant materials (fluorescent dyes and phosphorescent complexes). This composite approach enables fine-tuning of emission characteristics and color rendering properties while maintaining a consistent layered device structure, avoiding the need for completely different material systems for each color temperature.
3Ease of manufacture
If conventional white element structures are used, then manufacturing simplicity is maintained, but color rendering properties and efficiency deteriorate
Solution Approach 1:
The patent divides the white light-emitting device into four distinct functional layers: first blue fluorescent light-emitting layer, first green fluorescent light-emitting layer, second green phosphorescent light-emitting layer, and second red phosphorescent light-emitting layer. This segmentation allows each layer to be optimized for specific emission characteristics while maintaining a relatively simple overall structure that can be manufactured using standard vacuum deposition techniques.
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 enables the production of white light with adjustable color temperature, high average and special color rendering indices, and improved efficiency and longevity, facilitating minor design adjustments for optimal performance.
Implementation Method 1
the first light-emitting unit is designed to emit light by use of a phenomenon that a singlet exciton is generated by collision and fusion of two triplet excitons
Implementation Method 2
a blue fluorescent light-emitting layer
Implementation Method 3
a green fluorescent light-emitting layer
Implementation Method 4
a red phosphorescent light-emitting layer
Implementation Method 5
a green phosphorescent light-emitting layer
Data Source
AI summary
The organic electroluminescent element which is designed to emit white light in a range of a low color temperature to a high color temperature that is important for an illumination light source with a minor design change, and, moreover, has high color rendering property especially in an average color rendering index Ra and a special color rendering index R9 for red, while being highly efficient and long-life is obtained. The organic electroluminescent element includes: a transparent electrode; a first light-emitting unit including blue and green fluorescent light-emitting layers; an intermediate layer; a second light-emitting unit including red and green phosphorescent light-emitting layers; and a reflecting electrode. The first and second light-emitting units are stacked and the intermediate layer is interposed therebetween. The first light-emitting unit is designed to emit light by use of a phenomenon that a singlet exciton is generated by collision and fusion of two triplet excitons.