White Organic EL Element with Asymmetric Phosphorescent Layer Thickness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing organic electroluminescent elements face challenges in extending their lifetime while maintaining high luminance and suppressing luminance deterioration, particularly in multiunit elements where chromaticity changes over time.
Innovation Solution
A white organic electroluminescent element is designed with a multiunit structure, including a transparent electrode, a blue fluorescent light-emitting unit, an intermediate layer, and a second light-emitting unit with a red and green phosphorescent layer, where the film thickness of the red phosphorescent layer is significantly thinner than the green phosphorescent layer, and each layer is optimized with specific host materials and electrode positions to control emission intensity and color shift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a multiunit element structure is used to achieve high luminance, then the luminance intensity is improved, but the lifetime is reduced due to chromaticity deterioration
Solution Approach 1:
The light-emitting element is divided into multiple independent light-emitting units (first light-emitting unit with blue fluorescent layer, second light-emitting unit with red and green phosphorescent layers). Each unit can be independently optimized and the intermediate layer allows independent control of degradation in each unit, extending overall lifetime while maintaining high luminance
Solution Approach 2:
Different regions of the device have different layer configurations optimized for their specific functions. The first light-emitting unit uses fluorescent materials while the second uses phosphorescent materials, allowing each region to be optimized for its specific emission characteristics and degradation resistance
2Stability of the object's composition
If the red phosphorescent light-emitting layer is made thinner to control chromaticity, then the chromaticity stability is improved, but the red emission intensity may be reduced
Solution Approach 1:
The phosphorescent light-emitting layers are designed with asymmetric thickness ratios where the green phosphorescent layer is significantly thicker than the red phosphorescent layer (tG≥5tR). This asymmetric configuration compensates for the thin red layer by enhancing green emission, maintaining overall luminance while ensuring chromaticity stability
Solution Approach 2:
The thickness parameters of the phosphorescent layers are precisely controlled with specific ratios (tG≥5tR) to optimize the balance between chromaticity stability and emission intensity. By adjusting these dimensional parameters, the device achieves both thin red layer for stability and sufficient overall luminance
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 results in a long-life, high-luminance white organic electroluminescent element with suppressed luminance deterioration and controlled chromaticity change, extending the luminance lifetime by adjusting the emission spectrum to prioritize high luminosity functions.
Implementation Method 1
a blue fluorescent light-emitting layer containing a blue fluorescent light-emitting material
Implementation Method 2
a red phosphorescent light-emitting layer containing a red phosphorescent light-emitting material
Implementation Method 3
a green phosphorescent light-emitting layer containing a green phosphorescent light-emitting material
Implementation Method 4
a reflecting electrode
Data Source
AI summary
The present invention proposes a white organic electroluminescent element which is a multiunit element capable of emitting high intensity light that is important to a light source for lighting use, and can have an extended lifetime while suppressing deterioration in luminance. The organic electroluminescent element includes: a transparent electrode; and a first light-emitting unit including a blue fluorescent light-emitting layer containing a blue fluorescent light-emitting material; an intermediate layer; and a second light-emitting unit including a red phosphorescent light-emitting layer containing a red phosphorescent light-emitting material and a green phosphorescent light-emitting layer containing a green phosphorescent light-emitting material; and a reflecting electrode, wherein: the first and second light-emitting units are stacked having the intermediate layer interposed therebetween; and a film thickness (tR) of the red phosphorescent light-emitting layer and a film thickness (tG) of the green phosphorescent light-emitting layer satisfy a relation of 5*tR≦tG.