Conjugated Polymer Host for Organic EL Dopant Bleeding
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Solution Overview
Problem
In polymer-coat-type organic electroluminescent (EL) devices, the host material and light emitting dopant are not frequently applied due to bleeding of low molecular weight dopants, poor hole or electron trapping ability, and time-consuming development, especially when compared to deposition-type EL devices.
Innovation Solution
A polymer molecule with π conjugation is designed to prevent bleeding and enhance hole or electron trapping ability by incorporating specific functional groups, allowing for efficient red light emission and long lifespan in organic EL devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a solution containing host material and light emitting dopant is applied to a polymer-coat-type organic EL device, then high efficiency of light emission can be achieved, but bleeding of the light emitting dopant occurs during coating/drying
Solution Approach 1:
The invention uses a composite material system consisting of a conjugated polymer host and a light emitting dopant with specific molecular weight (100-10,000 Da). The dopant is designed to be soluble in the polymer matrix while maintaining sufficient molecular weight to prevent bleeding during the coating and drying processes, thus achieving both high light emission efficiency and compositional stability.
Solution Approach 2:
The invention changes the molecular weight parameter of the light emitting dopant to a specific range (100-10,000 Da) to optimize its behavior in the polymer-coat-type device. This parameter adjustment prevents the dopant from flowing out during drying while maintaining its light emitting functionality, resolving the contradiction between emission efficiency and compositional stability.
2Ease of manufacture
If the light emitting dopant has low molecular weight for easy processing, then it can be dissolved and coated, but it flows out from the surface layer during drying causing bleeding
Solution Approach 1:
The invention optimizes the molecular weight parameter of the light emitting dopant to a specific range (100-10,000 Da). This parameter setting is high enough to prevent bleeding during drying but low enough to maintain good solubility and coating processability, thus resolving the contradiction between ease of manufacture and compositional stability.
3Reliability
If the host material is a conjugated polymer for providing holes and electrons, then it enables electroluminescence, but the trapping ability of holes and electrons is very poor
Solution Approach 1:
The invention introduces the light emitting dopant as an intermediary substance between the conjugated polymer host and the charge carriers. The dopant molecules, with their specific molecular weight and chemical structure, serve as trapping sites for holes and electrons, mediating the charge transport process and improving trapping efficiency while the conjugated polymer continues to provide the electroluminescence function.
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 polymer molecule effectively traps holes and electrons, ensuring high efficiency and long-lasting red light emission in organic EL devices, improving luminance and half-life of the light emitting layer.
Implementation Method 1
A polymer molecule with π conjugation is designed to prevent bleeding and enhance hole or electron trapping ability, allowing for efficient red light emission in organic EL devices
Data Source
AI summary
A compound for organic EL includes a polymer molecule having molecules shown in the following Formulae 1 to 5 as constituent units.where R is an alkyl group, an aryl group, or an alkylaryl group,where R′ is hydrogen, an alkyl group, or an alkylaryl group.