Organic Light-Emitting Layer Concentration Gradient for Color Stability
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Solution Overview
Problem
Organic electric field light-emitting elements experience decreased emission efficiency and chromaticity changes due to carrier balance loss when current density changes, primarily caused by optical interference affecting the emission location, leading to color shifts.
Innovation Solution
Incorporating a light-emitting layer with two or more luminescent materials having different emission spectrums, where the concentration ratio of one luminescent material to another is gradually adjusted along the layer from the anode to the cathode, ensuring a specific concentration ratio and intensity ratio to minimize optical interference effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the light-emitting layer is made thicker to improve emission efficiency, then the emission intensity increases, but chromaticity changes occur due to optical interference
Solution Approach 1:
The patent applies local quality by creating a light-emitting layer with non-uniform luminescent material concentration distribution. Specifically, the concentration of luminescent materials is designed to vary at different positions within the layer, with higher concentration near the electrode and lower concentration toward the opposite side. This spatial variation in material properties compensates for optical interference effects, maintaining consistent chromaticity across the emission spectrum while preserving high emission intensity from the thicker layer structure.
Solution Approach 2:
The patent employs parameter changes by systematically varying the concentration of luminescent materials as a key parameter throughout the light-emitting layer. The concentration ratio of different luminescent materials is adjusted to satisfy specific mathematical relationships that counteract optical interference. This parameter optimization allows the layer to maintain both high emission intensity and stable chromaticity characteristics.
2Illumination intensity
If the concentration of luminescent materials is increased to improve emission efficiency, then the light output increases, but carrier balance is lost causing decreased permanence
Solution Approach 1:
The patent resolves this contradiction by optimizing the concentration parameter of luminescent materials within specific ranges. The total concentration is maintained at 1-50% to ensure high emission efficiency, while the specific distribution and ratio of different luminescent materials are controlled to preserve carrier balance. This parameter optimization ensures both high light output and long operational permanence.
Solution Approach 2:
The patent uses composite materials by combining multiple luminescent materials with different properties in a controlled concentration ratio. This composite approach allows the system to achieve high emission efficiency from the luminescent materials while the host material and specific composition ratios maintain carrier balance and improve operational permanence.
3Stability of the object's composition
If the concentration ratio of luminescent materials is adjusted to prevent chromaticity change, then emission color stability improves, but the complexity of manufacturing increases
Solution Approach 1:
The patent manages manufacturing complexity by establishing clear mathematical relationships for concentration ratios that must be satisfied. The concentration of luminescent materials follows specific formulas (e.g., C1(x) = a×x + b, C2(x) = c×x + d) that define the required spatial distribution. These quantified parameters provide manufacturing guidance while achieving chromaticity stability, balancing precision requirements with manufacturability.
Solution Approach 2:
The patent applies local quality by specifying different concentration requirements at different positions within the light-emitting layer. The concentration distribution is designed to vary systematically from one side of the layer to the other, with specific concentration ratios at different locations. This localized material property variation achieves chromaticity stability while providing clear manufacturing targets for each region of the layer.
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 approach enhances emission efficiency and permanence while preventing chromaticity changes when current density varies, maintaining consistent emission color by controlling the luminescent material concentrations within the light-emitting layer.
Implementation Method 1
a light-emitting layer containing a luminescent material(s) having two different emission spectrums at the different concentration ratio
Data Source
AI summary
An organic electric field light-emitting element, which contains: an anode; a cathode; and a light-emitting layer provided between the anode and the cathode, wherein the light-emitting layer contains two or more luminescent materials each giving a different emission peak, and a concentration ratio [(B/A)×100] in the light-emitting layer gradually increases along with the direction from an anode side of the light-emitting layer to a cathode side of the light-emitting layer, where A denotes a concentration of the luminescent material having the emission peak at the shortest wavelength side compared to the emission peaks of other luminescent materials, and B denote a concentration of the luminescent material having the emission peak at the longest wavelength side compared to the emission peaks of other luminescent materials, and wherein the light-emitting layer satisfies the relationship of: [(B/A)×100]≦10%.