Organic EL Element with Charge Generating Layers for Lighting
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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 proposed solution involves a multi-photon emission structure with a charge generating layer between light emitting units, where each unit includes specific functional layers and light emitting layers, such as phosphorescent and fluorescent layers, optimized in thickness and composition to achieve balanced light emission and efficient charge injection, resulting in white light with high color rendering index and low driving voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high luminance is achieved in organic EL elements, then light emission performance is improved, but lifespan decreases
Solution Approach 1:
The organic EL element is divided into multiple light emitting units (first, second, and third light emitting units) with different emission characteristics. Each unit contains specific organic compounds with different carrier transporting properties, allowing the element to distribute current across multiple units rather than concentrating it in a single unit, thereby reducing degradation at any one location and extending overall lifespan while maintaining high luminance.
2Illumination intensity
If multiple light emitting units are laminated in MPE structure, then luminance and efficiency are improved, but driving voltage increases and power efficiency decreases
Solution Approach 1:
Each light emitting unit is designed with specific local characteristics - the first light emitting unit uses organic compounds with electron transporting properties, the second unit uses compounds with hole transporting properties, and the third unit uses compounds with both electron and hole transporting properties. This local differentiation optimizes carrier injection and recombination in each unit, reducing overall driving voltage while maintaining high luminance and power efficiency.
Solution Approach 2:
The patent optimizes the thickness of organic layers in each light emitting unit to control electric field distribution and carrier transport. By adjusting layer thickness parameters, the element achieves balanced carrier injection across multiple units, reducing total driving voltage while maintaining high luminance output 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 organic electroluminescent elements to emit light with high luminance and efficiency while supporting a long lifespan, and the lighting device achieves improved power efficiency and color rendering, suitable for general lighting applications.
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
charges in a charge transfer complex move toward the cathode and the anode, and thus holes are injected into one light emitting unit positioned on the side of the cathode with sandwiching the charge generating layer, and electrons are injected into the other light emitting unit positioned on the side of the anode with sandwiching the charge generating layer
Data Source
AI summary
The present invention provides an organic electroluminescent element which includes a first light emitting unit (23) that is positioned on the side of a cathode (21) and includes a first light emitting layer (28A), a second light emitting unit (24) that is adjacent to the first light emitting unit (23) with sandwiching a first charge generating layer (26A) and includes a second light emitting layer (28B), and a third light emitting unit (25) that is adjacent to the second light emitting unit (24) with sandwiching a second charge generating layer (26B) and includes a third light emitting layer (28C), and in which differences of the total thickness of the first light emitting unit (23) and the total thickness of the third light emitting unit (25) with the total thickness of the second light emitting unit (24) are 30 nm to 70 nm.