OLED Emissive Layer Segmentation for Efficiency and Lifespan
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Solution Overview
Problem
Current organic light emitting diodes (OLEDs) face limitations in luminous efficiency and color purity, with fluorescent materials showing low efficiency and phosphorescent materials having short lifespan, making them unsuitable for commercial use.
Innovation Solution
The development of an organic light emitting diode with multiple emitting material layers, including blue, green, and red emitting layers, utilizing specific fluorescent and phosphorescent compounds, such as organometallic compounds and delayed fluorescent compounds, to enhance luminous efficiency and color purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescent material is used in OLED, then luminous efficiency is improved, but luminous lifespan becomes short
Solution Approach 1:
The emissive layer is divided into multiple distinct layers: a first emissive layer containing fluorescent compound and a second emissive layer containing phosphorescent compound. This segmentation allows each layer to contribute differently to light emission, combining the advantages of both fluorescent (long lifespan) and phosphorescent (high efficiency) materials while mitigating their individual disadvantages.
Solution Approach 2:
The patent employs a composite emissive layer structure that integrates both fluorescent and phosphorescent compounds in separate but adjacent layers. This composite approach enables the device to utilize both singlet and triplet excitons effectively, achieving high luminous efficiency while maintaining extended operational lifespan through the fluorescent component.
2Duration of action of moving object
If fluorescent material is used in OLED, then luminous lifespan is extended, but luminous efficiency becomes low
Solution Approach 1:
The patent merges the advantages of fluorescent and phosphorescent materials by placing both types of emitting layers in close proximity within the same device structure. The fluorescent layer ensures long operational lifespan while the phosphorescent layer boosts luminous efficiency, and their combined output achieves both extended lifespan and high efficiency simultaneously.
3Manufacturing precision
If multiple emitting material layers are added to improve color purity, then device complexity increases
Solution Approach 1:
Instead of adding multiple emitting layers in the vertical stacking direction (increasing device thickness and complexity), the patent arranges fluorescent and phosphorescent emitting layers side-by-side in the horizontal plane. This dimensional reorganization maintains color purity through spectral combination while minimizing increases in device complexity and manufacturing difficulty.
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 significantly improves luminous efficiency and color purity, enabling the production of OLEDs with lower driving voltages and extended luminous lifetime, suitable for commercial applications.
Implementation Method 1
holes injected from an anode and electrons injected from a cathode are recombined in an emitting material layer to form excitons with unstable energy state, and then the excitons relax into a ground state thereby emitting light
Implementation Method 2
a first green emitting material layer including a first green delayed fluorescent compound, and a second green emitting material layer disposed between the first green emitting material layer and the transmissive layer and including a second green delayed fluorescent compound
Data Source
AI summary
An organic light emitting device including: a substrate defining a first pixel region and a second pixel region; and an organic light emitting diode over the substrate. The organic light emitting diode includes a transmissive electrode, a reflective electrode facing the transmissive electrode and an emissive layer disposed between the transmissive electrode and the reflective electrode. The emissive layer includes a first emissive layer and a second emissive layer. The first emissive layer is in the first pixel region and includes: a first blue emitting material layer including a first blue fluorescent compound, and a second blue emitting material layer including a second blue fluorescent compound and a blue phosphorescent compound. The second emissive layer is in the second pixel region and includes: a first green emitting material layer including a first green delayed fluorescent compound, and a second green emitting material layer including a second green delayed fluorescent compound.