OLED Down Conversion Layer for White Light Generation
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Solution Overview
Problem
Current OLED technologies for generating white light face challenges such as low efficiency due to electron trapping, high manufacturing costs, and lower quantum efficiency of blue emitters, making them inefficient and difficult to produce.
Innovation Solution
A bluish-green OLED device coated with down conversion layers that absorb green light and emit orange or red light, eliminating the need for a red emitter and reducing manufacturing complexity by using only two emitting layers, thereby achieving high quantum efficiency and ease of fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a vertical RGB stack is used to generate white light, then all three primary colors can be emitted, but electron trapping caused by the red organic emitter reduces efficiency
Solution Approach 1:
The patent removes the red light-emitting component from the OLED structure entirely. Instead of using a red emitter that causes electron trapping and energy loss, the invention extracts only the necessary blue and green emitters, and generates the red component through down-conversion of blue light using organic dyes or phosphors in a conversion layer.
Solution Approach 2:
The patent introduces a down-conversion layer as an intermediary component between the blue/green OLED and the final white light output. This conversion layer contains organic dyes or phosphors that absorb blue light and re-emit it at longer wavelengths (green, yellow, orange, red), effectively mediating the conversion of high-energy blue photons into lower-energy red photons without requiring a red emitter.
2Adaptability or versatility
If a horizontal RGB stack is used to achieve tunable white light, then spectral output can be adjusted, but the device becomes expensive and difficult to manufacture
Solution Approach 1:
The patent simplifies the manufacturing process by extracting and eliminating the need for three separate emitting layers (RGB). Instead, it uses only blue and green emitting layers in the OLED, with a down-conversion layer that generates the remaining spectral components. This reduction from three emitters to two emitters plus conversion material significantly simplifies fabrication.
Solution Approach 2:
The patent achieves spectral tunability through parameter changes in the down-conversion layer rather than through complex multi-layer emitter structures. By adjusting the type, concentration, and combination of organic dyes or phosphors in the conversion layer, the spectral output can be tuned to produce different color temperatures and rendering properties, simplifying manufacturing while maintaining versatility.
3Illumination intensity
If a blue stack combined with phosphor is used, then white light can be generated, but the blue emitter offers lower quantum efficiency and reliability compared to green emitter
Solution Approach 1:
The patent inverts the conventional approach by using a green emitter as the primary high-efficiency light source rather than a blue emitter. The down-conversion layer converts green light into blue, cyan, and other wavelengths, effectively working backwards from the more reliable green emitter to generate the full spectrum, thereby achieving high quantum efficiency and reliability.
Solution Approach 2:
The patent employs composite materials in the down-conversion layer, combining multiple organic dyes or phosphors with different emission characteristics. This composite approach allows the system to convert green light into a broad spectrum including blue wavelengths, achieving white light output with high efficiency by leveraging the superior quantum efficiency of green emitters while still producing the necessary blue component through the composite conversion materials.
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 results in a highly efficient white light source with a high color rendering index, offering improved quantum efficiency, reduced electron trapping, and simplified manufacturing processes, while maintaining the advantages of blue and green OLEDs.
Implementation Method 1
The down conversion layer absorbs a part of the green light from the OLED device and emits one ore more of orange, red, and/or yellow light
Implementation Method 2
an electroluminescent apparatus is described which comprises of a bluish green OLED device
Data Source
AI summary
An electroluminescent apparatus includes an OLED device emitting light in the blue and green spectrums, and at least one down conversion layer. The down conversion layer absorbs at least part of the green spectrum light and emits light in at least one of the orange spectra and red spectra.