Laminated Organic Light Emitting Element with Concentration Gradient
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Solution Overview
Problem
Existing red light emitting organic electroluminescent elements face challenges in achieving high luminance efficiency and longer wavelength emission, with current materials either compromising on quantum efficiency or not sufficiently shifting the luminescence wavelength.
Innovation Solution
A light emitting element with a laminated structure comprising multiple layers of light emitting material in varying concentrations, where the concentration of the light emitting material in the highest layer is at least twice that of the lowest layer, allowing for efficient energy transfer and simultaneous achievement of high quantum efficiency and long wavelength emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single light emitting material concentration is used in the luminescent layer, then the manufacturing process is simple, but the element cannot achieve both high quantum efficiency and long wavelength emission simultaneously
Solution Approach 1:
The luminescent layer is divided into multiple sub-layers (first, second, and third luminescent layers) with different light emitting material concentrations. This segmentation allows each sub-layer to contribute differently to the overall emission characteristics, enabling simultaneous achievement of high quantum efficiency and long wavelength emission that cannot be achieved with a single uniform layer.
Solution Approach 2:
Different regions of the luminescent layer are assigned different light emitting material concentrations optimized for specific functions. The first luminescent layer has a concentration optimized for high quantum efficiency, while the second and third layers have concentrations optimized for long wavelength emission. This local optimization resolves the contradiction between manufacturing simplicity and performance consistency.
2Illumination intensity
If the light emitting material concentration is increased to achieve long wavelength emission, then the emission wavelength shifts to longer range, but the quantum efficiency decreases
Solution Approach 1:
The luminescent layer is segmented into multiple sub-layers with different light emitting material concentrations. The first luminescent layer uses a concentration optimized for high quantum efficiency, while the second and third layers use higher concentrations optimized for long wavelength emission. This segmentation allows the system to achieve both high quantum efficiency and long wavelength emission simultaneously, resolving the trade-off between these two parameters.
Solution Approach 2:
Different concentrations of light emitting material are applied in different regions of the luminescent layer. The first luminescent layer has a lower concentration optimized for efficiency, while the second and third layers have higher concentrations optimized for wavelength. This local quality differentiation resolves the contradiction between emission wavelength and quantum efficiency.
3Reliability
If multiple light emitting materials with different concentrations are laminated, then both high quantum efficiency and long wavelength emission are achieved, but the device structure becomes more complex
Solution Approach 1:
The luminescent layer is segmented into three sub-layers with progressively different light emitting material concentrations. While this increases structural complexity compared to a single layer, it enables simultaneous optimization of quantum efficiency and emission wavelength. The segmentation is systematic and manageable, with each layer having a specific functional role.
Solution Approach 2:
The luminescent layer is designed with local quality variations through different material concentrations in different sub-layers. The first layer has concentration optimized for efficiency, while the second and third layers have concentrations optimized for wavelength. This local optimization achieves superior performance while maintaining a relatively simple overall device architecture.
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 laminated structure enables a red light emitting element with high luminance efficiency and long wavelength emission, maintaining quantum efficiency while effectively shifting the luminescence wavelength, outperforming single-layer structures and alternative lamination concepts.
Implementation Method 1
the concentration of the light emitting material in the highest layer is at least twice that of the lowest layer, allowing for efficient energy transfer
Implementation Method 2
electrons and holes recombine in a luminescent layer to release energy as light when the electron undergo the transition from the conduction band to the valence band
Data Source
AI summary
The present invention provides a light emitting element comprising a pair of electrodes and one or more organic compound layers including a luminescent layer disposed between the pair of electrodes. In this structure, the luminescent layer includes at least one charge transport material and at least one light emitting material, and comprises a laminated structure having two or more laminates including a plurality of layers including the light emitting material in different concentrations.