OLED with Composite Phosphorescent and Fluorescent Layers
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Solution Overview
Problem
Conventional organic light emitting diodes (OLEDs) face limitations in luminous efficiency due to the use of fluorescent materials, which only utilize singlet excitons for emission, resulting in low efficiency and limited display performance.
Innovation Solution
The implementation of an OLED structure that includes a reflective electrode, a transparent electrode, and an organic light emitting layer with a combination of phosphorescent and fluorescent emitting layers, where the fluorescent layer is positioned closer to the transparent electrode, enhancing emission efficiency and display performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If fluorescent materials are used as emitters in OLED, then the device structure is simple, but the luminous efficiency is low because only singlet excitons are utilized for emission
Solution Approach 1:
The patent employs composite emitting layers that integrate both phosphorescent and fluorescent materials within the same OLED structure. The phosphorescent emitting layer utilizes triplet excitons while the fluorescent emitting layer utilizes singlet excitons, creating a composite system that harvests both types of excitons to significantly improve luminous efficiency beyond what single-material layers can achieve
Solution Approach 2:
The emitting layer is segmented into multiple distinct layers with different emission characteristics. The patent divides the emitting layer into a phosphorescent emitting layer (first emitting layer) and a fluorescent emitting layer (second emitting layer), allowing each segment to specialize in utilizing different exciton types, thereby collectively improving overall device efficiency
2Productivity
If phosphorescent and fluorescent emitting layers are combined, then luminous efficiency improves, but the device structure becomes more complex
Solution Approach 1:
The patent resolves structural complexity by transitioning from a single-layer emitting structure to a multi-layer emitting structure, adding the dimensional aspect of vertical layering. This dimensional change allows simultaneous incorporation of phosphorescent and fluorescent materials in distinct layers, enabling high luminance output while managing complexity through structured organization
Solution Approach 2:
Different regions of the emitting layer are assigned different functional qualities. The phosphorescent emitting layer is optimized for triplet exciton utilization while the fluorescent emitting layer is optimized for singlet exciton utilization. Each local region has tailored material composition and properties to maximize its specific emission function, improving overall productivity
3Measurement precision
If fluorescent layer is positioned closer to transparent electrode, then color purity and emission efficiency improve, but manufacturing precision requirements increase
Solution Approach 1:
The patent establishes a predetermined layer stacking sequence during device design and fabrication planning. The fluorescent emitting layer is pre-positioned closer to the transparent electrode in the design stage, and this predetermined configuration is maintained through the manufacturing process, allowing color purity optimization to be achieved through standard fabrication procedures rather than requiring post-manufacturing adjustment
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 luminance and color purity by utilizing both singlet and triplet excitons for emission, leading to higher efficiency and extended lifespan of the OLED.
Implementation Method 1
The first emitting layer is a first phosphorescent emitting layer
Implementation Method 2
The second emitting layer is a first fluorescent emitting layer
Implementation Method 3
a reflective electrode; a transparent electrode facing the reflective electrode
Data Source
AI summary
An organic light emitting diode (OLED) and an organic light emitting device (such as a display device or a lighting device) comprising the OLED are described. The OLED includes a reflective electrode; a transparent electrode facing the reflective electrode; and an organic light emitting layer comprising a first emitting part and a second emitting part, positioned between the reflective electrode and the transparent electrode. The first emitting part comprises a first emitting layer and a second emitting layer, while the second emitting part comprises a third emitting layer and a fourth emitting layer. The first emitting layer is a first phosphorescent emitting layer, and the second emitting layer is a first fluorescent emitting layer. The third emitting layer can be a second phosphorescent emitting layer. The first fluorescent emitting layer is closer to the transparent electrode than the first phosphorescent emitting layer.