Light-Emitting Element With Segmented Layers And Optimized Spacing
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Solution Overview
Problem
Light-emitting elements with metal films of high reflectance, such as silver, suffer from surface plasmon resonance, leading to lower light extraction efficiency due to scattering or absorption of light near the metal film surfaces, which reduces the overall emission efficiency of light-emitting devices.
Innovation Solution
A light-emitting element structure with multiple light-emitting layers, where the emission spectrum of one layer peaks at a longer wavelength than the other, and the distance between electrodes is optimized to minimize optical path lengths, reducing absorption or scattering and enhancing light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a metal film with high reflectance (e.g., silver) is used as one of the electrodes in a microcavity structure, then light reflectance is improved, but light extraction efficiency deteriorates due to surface plasmon resonance causing scattering or absorption of light
Solution Approach 1:
The single light-emitting layer is divided into multiple light-emitting layers (first light-emitting layer and second light-emitting layer) with different emission spectra. This segmentation allows different layers to emit at different wavelengths, reducing the impact of surface plasmon resonance at any single wavelength and improving overall light extraction efficiency while maintaining high reflectance from the metal film electrode.
Solution Approach 2:
Different regions (light-emitting layers) are assigned different emission characteristics - the first light-emitting layer emits at a longer wavelength while the second light-emitting layer emits at a shorter wavelength. This local differentiation in emission properties allows optimization for different parts of the spectrum, mitigating the harmful effects of surface plasmon resonance which affects different wavelengths differently.
2Loss of energy
If the distance between electrodes is reduced to optimize optical path length, then light extraction efficiency is improved, but device design flexibility deteriorates
Solution Approach 1:
The invention optimizes specific parameters including the distance between electrodes (set to 100 nm or less) and the thickness of each light-emitting layer (first layer: 5-20 nm, second layer: 5-20 nm) to minimize optical path length and reduce absorption/scattering losses. These parameter optimizations improve light extraction efficiency while maintaining manufacturability through precise control of thin film deposition.
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 proposed structure achieves high emission efficiency and low power consumption by minimizing light loss through optimized optical path lengths and layer positioning, resulting in improved light extraction and emission characteristics.
Implementation Method 1
a light-emitting element in which a light-emitting layer capable of providing light emission by application of an electric field is provided between a pair of electrodes
Implementation Method 2
light might be scattered or absorbed in the vicinity of a surface of the metal film with high reflectance under the influence of surface plasmon resonance (SPR)
Data Source
AI summary
To provide a novel light-emitting element or a novel light-emitting device with high emission efficiency and low power consumption, a light-emitting element having a plurality of light-emitting layers between a pair of electrodes includes a lower electrode, a first light-emitting layer over the lower electrode, a charge-generation layer over the first light-emitting layer, a second light-emitting layer over the charge-generation layer, and an upper electrode over the second light-emitting layer. An emission spectrum of the first light-emitting layer peaks at a longer wavelength than an emission spectrum of the second light-emitting layer. A distance of between a bottom surface of the upper electrode and a bottom surface of the first light-emitting layer is less than or equal to 130 nm.