OLED Charge Balance Control Layer Alleviates Luminance Reduction
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Solution Overview
Problem
Organic light-emitting diodes (OLEDs) face significant luminance reduction issues in low dynamic ranges, making it difficult to maintain color reproduction and expression, especially at low voltages, due to large luminance changes, which complicates stable white color implementation.
Innovation Solution
Incorporating a light-emitting layer with amine derivative compounds and a charge balance control layer featuring anthracene derivative compounds, strategically positioned between the electrodes, to enhance luminance efficiency and reduce luminance fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional organic light-emitting diode structures are used, then device simplicity is maintained, but luminance reduction occurs in low dynamic range
Solution Approach 1:
The device is divided into distinct functional layers: a light-emitting layer containing amine derivative compounds and a separate charge balance control layer containing anthracene derivative compounds. This segmentation allows each layer to perform its specific function optimally - the light-emitting layer generates excitons and light, while the charge balance control layer regulates charge carrier density, thereby resolving the luminance stability issue without requiring complete structural redesign.
Solution Approach 2:
The charge balance control layer acts as an intermediary between the light-emitting layer and the electron injection layer. It mediates the flow of charge carriers, controlling the electron density that reaches the light-emitting layer. This intermediary function prevents excessive electron injection that causes luminance reduction in low dynamic range, while maintaining overall device simplicity through a single additional layer.
2Illumination intensity
If high electron density is introduced to improve luminance efficiency, then light emission intensity increases, but luminance reduction in low dynamic range worsens
Solution Approach 1:
The patent changes the chemical composition parameters of the charge balance control layer by incorporating anthracene derivative compounds with specific molecular structures and electron mobility characteristics. This parameter change optimizes the electron transport properties, allowing the layer to maintain appropriate electron density under varying voltage conditions. The result is improved luminance efficiency at high brightness while preventing luminance reduction at low brightness levels.
Solution Approach 2:
Different regions of the device have different material compositions optimized for their specific functions. The charge balance control layer contains anthracene derivative compounds specifically positioned between the light-emitting layer and electron injection layer to locally control electron density. This local quality approach ensures that electron density is regulated precisely where needed, maintaining luminance stability without sacrificing overall luminance efficiency.
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 solution effectively alleviates luminance reduction rates in low dynamic ranges, improving color reproducibility and stability across various voltage levels by optimizing charge balance and exciton density in the OLEDs.
Implementation Method 1
when a voltage is applied between the anode and the cathode, the anode injects holes which are then transferred to the light-emitting layer via the hole transport layer while electrons injected from the cathode move to the light-emitting layer via the electron transport layer. In the luminescent zone, the carriers such as holes and electrons recombine to produce an exciton. When the exciton returns to the ground state from the excited state, the molecule of the light-emitting layer emits light.
Implementation Method 2
This is based on the principle whereby, when a dopant which is smaller in energy band gap than a host forming a light-emitting layer is added in a small amount to the light-emitting layer, excitons are generated from the light-emitting layer and transported to the dopant, emitting light at high efficiency.
Data Source
AI summary
The present disclosure relates to an organic light-emitting diode which can operate at a low voltage with high efficiency and exhibits the effect of having an alleviated luminance reduction rate in a low dynamic range. More particularly, the organic light-emitting diode comprises: a first electrode; a second electrode facing the first electrode; and a light-emitting layer and a charge balance control layer arranged sequentially between the first and the second electrode, wherein the light-emitting layer includes at least one of amine derivative compounds represented by the following Chemical Formula A and the charge balance control layer includes at least one of anthracene derivative compounds represented by the following Chemical Formula B or C. The structures of Chemical Formulas A, B, and C are as defined in the specification.