Organic EL Element with Multi-Photon Emission Structure
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Solution Overview
Problem
Organic electroluminescent elements face challenges in achieving high luminance and efficiency while maintaining a long lifespan, particularly when used in lighting devices, as high luminance tends to decrease lifespan and increasing the number of light emitting units in MPE structures increases driving voltage and reduces power efficiency.
Innovation Solution
The organic electroluminescent element employs a multi-photon emission (MPE) structure with a laminate configuration of light emitting units and charge generating layers, utilizing specific materials and layer thicknesses to optimize electron and hole injection, and includes phosphorescent and fluorescent light emitting layers to achieve high luminance and efficiency, with the thickness of functional layers carefully controlled to balance efficiency and voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high current is applied to achieve high luminance, then luminance is improved, but lifespan decreases
Solution Approach 1:
The organic EL element is divided into multiple light emitting units (first light emitting unit and second light emitting unit) connected in series between cathode and anode. Each unit contains its own light emitting layer and charge generating layer, allowing the total luminance requirement to be distributed across multiple units rather than concentrating high current through a single unit, thereby extending lifespan while maintaining high luminance
Solution Approach 2:
Multiple light emitting units are combined in series to achieve high luminance through additive effect. The first and second light emitting units work together to provide the required luminance output while each unit operates at lower current levels, resolving the contradiction between high luminance and long lifespan
2Illumination intensity
If multiple light emitting units are laminated in MPE structure to increase luminance, then luminance is improved, but driving voltage increases and power efficiency decreases
Solution Approach 1:
Charge generating layers are introduced as intermediary layers between the first and second light emitting units. These layers facilitate efficient charge generation and transfer between units, reducing the overall driving voltage required for the multi-unit structure while maintaining high luminance output, thus improving power efficiency
Solution Approach 2:
The thickness of functional layers including charge generating layers and light emitting layers is optimized to specific ranges (charge generating layer: 5-50 nm, light emitting layer: 20-200 nm) to balance voltage reduction and luminance maintenance. By adjusting these parameters, the element achieves low voltage driving while preserving high luminance and power efficiency
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 enables the organic electroluminescent element to emit light with high luminance and efficiency while supporting a long lifespan, and the lighting device achieves improved power efficiency with low voltage driving, maintaining high color rendering and luminance.
Implementation Method 1
When a voltage is applied between the cathode and the anode, light is emitted due to excitons that are generated when electrons injected into the light emitting layer from the side of the cathode and holes injected into the light emitting layer from the side of the anode recombine in the light emitting layer
Implementation Method 2
the light emitting layer includes a first phosphorescent light emitting layer, a first isolation layer, a blue fluorescent light emitting layer
Implementation Method 3
a blue fluorescent light emitting layer, a second isolation layer, and a second phosphorescent light emitting layer
Data Source
Figure 1
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Figure 4~5
AI summary
In order to provide an organic electrolumin-descent element which is sable to emit light highly efficiently with high luminance, and which is suited to a lounger service life, an organic electroluminescent element according two the present invention is provided with: a first light emitting unit (23) which is positioned on a negative electrode (21) side and comprises a first light emitting layer (28A); a second light emitting unit (24) which is adjacent to the first light emitting unit (23), with a first charge generation layer (26A) being interposed therebetween, and comprises a second light emitting layer (28B); and a third light emitting unit (25) which is adjacent to the second light emitting unit (24), with a second charge generation layer (26B) being interposed therebetween, and comprises a third light emitting layer (28C). The difference between the total thickness of the second light emitting unit (24) and the total thickness of the first light emitting unit (23), and the differences between the total thickness of the second light emitting unit (24) and the total thickness of the third light emitting unit (25) are 30-70 nm, respectively.