Tandem Blue OLED Emission Layer Structure for Efficiency and Color Purity
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Solution Overview
Problem
Existing OLED technologies face limitations in emitting efficiency and color purity, particularly in blue OLEDs, which affect the performance of flat panel display devices.
Innovation Solution
The use of a tandem structure in the blue emitting layer, comprising a first blue emitting layer with a phosphorescent compound and a second blue emitting layer with a phosphorescent and fluorescent compound, positioned between electrodes, enhances emitting efficiency and color purity by optimizing the energy transfer and emission spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single blue emitting layer is used in OLED, then the device structure is simple, but the emitting efficiency and color purity are limited
Solution Approach 1:
The blue emitting layer is divided into two distinct layers: a first blue emitting layer containing a first phosphorescent compound and a second blue emitting layer containing a second phosphorescent compound and a fluorescent compound. This segmentation allows each layer to contribute differently to the overall emission, with the first layer providing high efficiency phosphorescent emission and the second layer enhancing color purity through fluorescent contribution, thereby resolving the contradiction between structural simplicity and emitting performance.
Solution Approach 2:
The patent employs composite emitting materials in both layers, combining phosphorescent and fluorescent compounds in the second blue emitting layer. This composite approach enables synergistic effects where the phosphorescent compound provides high efficiency and the fluorescent compound enhances color purity, achieving superior overall performance that neither material could achieve alone.
2Ease of manufacture
If a single blue emitting layer is used in OLED, then the manufacturing process is simple, but the color purity is limited
Solution Approach 1:
By segmenting the emitting layer into two distinct layers with different material compositions, the patent enables independent optimization of each layer's function. The first layer can be optimized for phosphorescent emission efficiency while the second layer is optimized for color purity through fluorescent contribution, allowing precise control over the final emission characteristics without complicating the overall manufacturing process.
Solution Approach 2:
Each emitting layer is designed with specific local quality characteristics: the first blue emitting layer is optimized for phosphorescent emission with specific compound properties, while the second blue emitting layer is optimized for color purity with its unique combination of phosphorescent and fluorescent compounds. This local optimization approach enables precise control over the emission spectrum and color purity while maintaining manufacturability.
3Device complexity
If conventional single-layer blue emitting structure is used, then the energy transfer is straightforward, but the emitting efficiency is limited
Solution Approach 1:
The emission process is segmented into two sequential stages across two layers: the first blue emitting layer performs initial phosphorescent emission with high efficiency, and the second blue emitting layer receives this energy and converts it to fluorescent emission with enhanced color purity. This segmentation of the energy transfer process allows each layer to optimize its specific function, achieving overall superior emitting efficiency while maintaining manageable energy transfer complexity.
Solution Approach 2:
The interface between the two emitting layers acts as an intermediary for energy transfer. The first phosphorescent compound emits energy that is transferred to the second phosphorescent and fluorescent compound system, enabling efficient energy utilization. This intermediary energy transfer mechanism allows the system to overcome the limitations of single-layer structures by facilitating controlled energy flow between layers with different emission characteristics.
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 improves the emitting efficiency and color purity of OLEDs, specifically in blue pixels, leading to better performance in flat panel displays by increasing brightness and maintaining high color accuracy.
Implementation Method 1
the first blue emitting layer includes a first phosphorescent compound, and the second blue emitting layer includes a second phosphorescent compound and a first fluorescent compound
Implementation Method 2
the second blue emitting layer includes a second phosphorescent compound and a first fluorescent compound
Implementation Method 3
The OLED emits light by injecting electrons from a cathode as an electron injection electrode and holes from an anode as a hole injection electrode into an emitting material layer, combining the electrons with the holes, generating an exciton, and transforming the exciton from an excited state to a ground state
Data Source
AI summary
The present disclosure relates to an organic light emitting diode, and an organic light emitting device including the same. An organic light emitting diode includes a first electrode; a second electrode facing the first electrode; and a first emitting part including a first blue emitting material layer and positioned between the first and second electrodes, the first blue emitting material layer including a first blue emitting layer and a second blue emitting layer, wherein the second blue emitting layer is positioned between the first blue emitting layer and the second electrode, wherein the first blue emitting layer includes a first phosphorescent compound, and the second blue emitting layer includes a second phosphorescent compound and a first fluorescent compound, wherein each of the first and second phosphorescent compounds is represented by Formula 5, and wherein the first fluorescent compound is represented by Formula 7.