Stacked Organic EL Element with Charge Generating Layers
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Solution Overview
Problem
Conventional organic electroluminescent elements struggle to provide white light that balances high color temperature, luminous efficiency, and color rendering properties simultaneously, making them unsuitable for both display and lighting devices.
Innovation Solution
An organic electroluminescent element with a multi-photon emission structure, where multiple light emitting units, including blue, red/green, and red-green units, are stacked with charge generating layers, producing white light with a continuous emission spectrum across 380 nm to 780 nm, peak wavelengths in specific bands, and optimized color rendering indices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single light emitting unit is used, then the device structure is simple, but it cannot provide white light with balanced color temperature, luminous efficiency, and color rendering properties
Solution Approach 1:
The organic EL element is divided into multiple light emitting units (first light emitting unit with red phosphorescent material, second light emitting unit with green phosphorescent material, third light emitting unit with blue phosphorescent material), each responsible for emitting a specific color. This segmentation allows each unit to be optimized for its specific wavelength while collectively producing high-quality white light with balanced color temperature, luminous efficiency, and color rendering properties.
Solution Approach 2:
The patent employs composite light emitting layers combining different phosphorescent materials (red, green, and blue phosphorescent dopants) within separate light emitting units. These composite structures enable simultaneous emission of multiple wavelengths that combine to form white light with superior color rendering indices (Ra≥90, R9≥90) and high color temperature (6504K), while maintaining high luminous efficiency.
2Adaptability or versatility
If multiple light emitting units are stacked to achieve high-quality white light, then color temperature and color rendering properties improve, but the device complexity increases
Solution Approach 1:
Each light emitting unit serves multiple functions: it acts as both an emission source for its specific color and as part of the overall white light generation system. The charge generating layers between units serve dual purposes of electrical insulation and charge redistribution, enabling the stacked structure to function as a unified multi-color emission system without requiring separate control circuits for each unit.
Solution Approach 2:
Charge generating layers are introduced as intermediary components between adjacent light emitting units. These layers facilitate charge transfer and electrical insulation between units, enabling the stacked configuration to operate cohesively. The intermediaries allow independent optimization of each light emitting unit while maintaining overall system integration and simplifying the control architecture.
3Ease of manufacture
If conventional single-unit organic EL elements are used, then manufacturing is simpler, but luminous efficiency and color rendering properties cannot be simultaneously optimized
Solution Approach 1:
The patent optimizes multiple parameters including the selection of phosphorescent materials with specific emission wavelengths, adjustment of dopant concentrations in each light emitting unit, and control of layer thicknesses. By systematically varying these parameters across the three stacked units, the element achieves peak luminous efficiency in each color channel while maintaining balanced color rendering, with the combined output reaching Ra≥90 and R9≥90.
4Loss of energy
If multiple light emitting units are used to achieve high luminous efficiency, then energy utilization improves, but the element structure becomes more complex
Solution Approach 1:
The stacked structure enables continuous utilization of electrical energy across multiple emission channels. As current passes through the element, each light emitting unit continuously converts electrical energy to light in its optimal wavelength range, minimizing energy loss. The charge generating layers ensure continuous charge supply to all units, maintaining high luminous efficiency throughout operation while the modular structure keeps fabrication manageable through standardized layer sequences.
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 solution achieves white light with high color temperature, high luminous efficiency, and excellent color rendering properties, making it suitable for both display and lighting devices, while maintaining high-luminance and long-life performance.
Implementation Method 1
An organic electroluminescent element (hereafter, also referred to as 'organic EL element' for short) is a self-luminescent element including a light emitting layer, made of an organic compound, between a cathode and an anode facing each other. When voltage is applied between the cathode and the anode, electrons injected into the light emitting layer from the cathode side and holes injected into the light emitting layer from the anode side recombine in the light emitting layer to form excitons and the excitons causes the organic EL element to emit light.
Implementation Method 2
the blue light emitting layer is formed of a blue phosphorescent light emitting layer containing a blue phosphorescent material
Data Source
AI summary
This organic EL element has one blue light emitting unit, and has a continuous emission spectrum. The organic EL element has one or two peak wavelengths in a blue light wavelength range of 440 nm-490 nm within this emission spectrum, the correlated color temperature of white light is 3300K or greater, and according to a special color rendering index (Ri) of white light, R6 is 60 or greater and R12 is 30 or greater.