Organic Electroluminescence Element Stabilization
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Solution Overview
Problem
Organic electroluminescent elements exhibit a high initial drop in luminance when subjected to constant current drive, leading to 'burning' issues in display applications, with insufficient investigation into the initial drop's impact on durability.
Innovation Solution
Incorporating specific compounds with carbazole or fluorene structures in the anode-side layer and the light emitting layer, including compounds represented by general formulas (A) and (B), to stabilize the organic layers and reduce initial luminance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional light emitting materials are used in the light emitting layer, then the element can emit light with low voltage driving, but the luminance shows a high initial drop rate immediately after start of light emission
Solution Approach 1:
The patent changes the chemical structure parameters of the light emitting material by incorporating specific carbazole or fluorene structures with defined molecular formulas. This structural modification alters the electrical and optical properties of the material, reducing the initial luminance drop while maintaining efficient light emission under low voltage driving conditions.
Solution Approach 2:
The patent uses composite material strategy by combining the light emitting material (containing carbazole or fluorene structures) with a host material in the light emitting layer. This composite approach allows the light emitting material to benefit from the host material's properties while the specific molecular structure mitigates the initial luminance drop, achieving both efficiency and stability.
2Illumination intensity
If the element is driven with constant current for continuous lighting, then high luminance can be achieved, but burning occurs due to high initial luminance drop in pixel groups
Solution Approach 1:
By modifying the molecular structure parameters of the light emitting material to include specific carbazole or fluorene structures, the patent changes the operational characteristics of the element. This allows continuous constant current driving at high luminance levels without the severe initial drop that causes burning, improving luminance uniformity across pixel groups.
Solution Approach 2:
The patent employs organic light emitting materials that can be deposited using cost-effective methods such as solution processing or simple vapor deposition. These materials, while potentially having limited individual lifetimes, provide a economical solution for achieving high luminance without burning when properly formulated with the specified molecular structures.
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 proposed solution significantly reduces the initial drop in luminance, enhancing the driving durability of organic electroluminescent elements and mitigating 'burning' effects in display applications.
Implementation Method 1
Incorporating specific compounds with carbazole or fluorene structures in the anode-side layer and the light emitting layer, including compounds represented by general formulas (A) and (B), to stabilize the organic layers and reduce initial luminance degradation
Data Source
AI summary
An organic electroluminescent element having a small reduction rate in the luminance immediately after the start of light emission is provided. The organic electroluminescent element includes a substrate, a pair of electrodes including an anode and a cathode, disposed on the substrate, a light emitting layer disposed between the electrodes, and at least one organic layer disposed between the light emitting layer and the anode, in which at least one kind of a specific compound including a fluorene structure is contained in at least one organic layer between the light emitting layer and the anode, and at least one kind of a specific compound including a carbazole structure or a fluorene structure is contained as a light emitting material in the light emitting layer.