OLED Hyperfluorescence Layering for Efficiency
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Solution Overview
Problem
Organic light emitting display devices face limitations in emitting efficiency due to the reliance on singlet excitons from fluorescent materials, which restricts their performance.
Innovation Solution
The use of a layered structure in organic light emitting diodes, where a fluorescent emitting layer is positioned between a reflective electrode and a transparent electrode, and a phosphorescent emitting layer is positioned closer to the transparent electrode, enhancing emitting efficiency through hyper-fluorescence by efficiently transferring energy and reducing full width at half maximum (FWHM).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If only fluorescent emitting layers are used in OLEDs, then the device structure is simple, but the emitting efficiency is limited due to reliance on singlet excitons only
Solution Approach 1:
The emitting layer is segmented into multiple functional parts: a fluorescent emitting layer containing singlet excitons and a phosphorescent emitting layer containing triplet excitons. This segmentation allows both singlet and triplet excitons to contribute to light emission, thereby improving emitting efficiency while maintaining a manageable layered structure.
Solution Approach 2:
The patent employs composite material strategy by combining fluorescent and phosphorescent emitting materials in a single OLED device. The fluorescent emitting layer and phosphorescent emitting layer work together as composite functional units, enabling the device to utilize both singlet and triplet excitons for light emission, thus resolving the efficiency limitation of pure fluorescent materials.
2Reliability
If phosphorescent emitting layer is added to improve efficiency, then quantum efficiency increases, but the device structure becomes more complex
Solution Approach 1:
The emitting layer is divided into distinct fluorescent and phosphorescent segments, each optimized for specific exciton types. This segmentation enables independent optimization of each layer's composition and thickness, improving quantum efficiency while keeping the overall structure organized and manufacturable.
Solution Approach 2:
Different regions of the emitting layer structure are assigned different qualities: the fluorescent emitting layer is optimized for singlet exciton utilization with specific host-guest combinations, while the phosphorescent emitting layer is optimized for triplet exciton utilization with heavy metal complexes. This local quality differentiation maximizes overall device performance.
3Manufacturing precision
If multiple emitting layers are stacked, then emission spectra narrow (lower FWHM), but manufacturing precision requirements increase
Solution Approach 1:
The emitting layer is segmented into multiple thin sub-layers with controlled thicknesses. Each segment contributes to the overall emission profile, and by adjusting the thickness and composition of individual segments, the FWHM can be precisely controlled without requiring extreme manufacturing precision in any single layer.
Solution Approach 2:
The patent utilizes parameter changes in the emitting layer structure, such as varying the thickness of fluorescent and phosphorescent layers, adjusting dopant concentrations, and modifying host-guest ratios. These parameter adjustments enable fine-tuning of emission spectra and FWHM while maintaining ease of manufacture through conventional OLED fabrication processes.
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 lifespan of the OLEDs by intensifying the micro-cavity effect and providing higher quantum efficiency and narrower emission spectra.
Implementation Method 1
a phosphorescent emitting layer is positioned closer to the transparent electrode, enhancing emitting efficiency through hyper-fluorescence by efficiently transferring energy
Implementation Method 2
efficiently transferring energy and reducing full width at half maximum (FWHM)
Implementation Method 3
a fluorescent emitting layer is positioned between a reflective electrode and a transparent electrode
Implementation Method 4
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
An organic light emitting display device includes a substrate including first to third pixel regions; and an organic light emitting diode including a transparent electrode, a reflective electrode and a light emitting layer between the transparent electrode and the reflective electrode. The light emitting layer in the organic light emitting diode in the first pixel region includes a first emitting part including a first emitting material layer and a second emitting part including a second emitting material layer. The light emitting layer in the organic light emitting diode in the second pixel region includes a third emitting part including a third emitting material layer and fourth emitting part including a fourth emitting material layer. Each of the first and fourth emitting material layers is a fluorescent emitting layer, and each of the second and third emitting material layers is a phosphorescent emitting layer.