Organic Light-Emitting Element With Dual Emission Layers for Charge Balance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing organic white light-emitting elements face challenges in improving light emission characteristics and driving durability, particularly in terms of charge balance and dopant concentrations in the light-emitting layers.
Innovation Solution
The organic light-emitting element is configured with two light-emitting layers, where the first light-emitting layer has a lower hole-trapping ability than the electron-trapping ability of the second layer, achieved by specific HOMO and LUMO level differences and controlled dopant concentrations, along with the use of electron- and hole-blocking layers to confine charges and delocalize the recombination region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the concentrations of light-emitting dopants are increased to improve light emission intensity, then the light emission characteristic improves, but the charge balance in the light-emitting layers deteriorates
Solution Approach 1:
The light-emitting layer is divided into two distinct layers: a first light-emitting layer containing a first light-emitting dopant and a second light-emitting layer containing a second light-emitting dopant. This segmentation allows each layer to be optimized independently for charge balance and light emission, resolving the contradiction between improving light intensity and maintaining charge balance.
2Reliability
If the dopant concentrations are adjusted to improve charge balance, then the charge balance improves, but the light emission characteristic deteriorates
Solution Approach 1:
By segmenting the light-emitting layer into two layers with different dopant concentrations, the first layer can be optimized for charge balance while the second layer is optimized for light emission intensity, thereby resolving the contradiction between these two parameters.
Solution Approach 2:
Different regions (layers) of the light-emitting structure are given different dopant concentrations tailored to their specific functions: the first layer has concentrations optimized for charge balance, while the second layer has concentrations optimized for light emission, allowing each region to perform its intended function effectively.
3Device complexity
If conventional single-layer configurations are used to simplify device structure, then device complexity is reduced, but light emission efficiency and driving durability deteriorate
Solution Approach 1:
The light-emitting layer is segmented into two layers with different dopant concentrations and compositions, enabling independent optimization of charge balance and light emission properties, which improves both light emission efficiency and driving durability despite increased structural complexity.
Solution Approach 2:
The device employs a composite structure with two light-emitting layers containing different dopants and host materials, allowing the system to achieve superior performance in both light emission efficiency and driving durability by combining materials with complementary properties.
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 enhances light emission efficiency and extends the driving durability of the organic light-emitting element by reducing excitation loss and suppressing deterioration.
Implementation Method 1
An organic light-emitting element (also referred to as 'organic electroluminescence element' or 'organic EL element' in some cases) is an element that includes a positive electrode, a negative electrode, and an organic compound layer disposed between these electrodes and including a light-emitting layer, and emits light by energizing the organic compound layer
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3B
AI summary
The present disclosure provides an organic light-emitting element including a first light-emitting layer that includes a first organic compound, a first light-emitting material, and a second light-emitting material and including a second light-emitting layer that includes a second organic compound and a third light-emitting material, wherein the hole-trapping ability of the first light-emitting layer is mitigated and the recombination region of holes and electrons is kept away from the electrode side of the first light-emitting layer and is also localized in the light-emitting layer by controlling the difference between the HOMO levels of the first light-emitting material and first organic compound in the first light-emitting layer to be smaller than the difference between the LUMO levels of the second organic compound and third light-emitting material in the second light-emitting layer, and reducing the content of the light-emitting material in the first light-emitting layer.