Organic Electroluminescent Device Angular Light Control
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Solution Overview
Problem
Organic electroluminescent devices with a multi-photon emission structure face challenges in controlling the distribution characteristics of light emitted into a substrate, leading to inefficient light extraction and suboptimal optical design for display and lighting applications.
Innovation Solution
An organic electroluminescent device with a stacked structure of light emitting units, including blue, red/green, and blue light emitting units, where the blue light emitting unit is formed of a blue fluorescent or phosphorescent layer, and the red/green unit is formed of a mixed red and green phosphorescent or fluorescent layer, with a charge generating layer sandwiched between each pair, optimizing light emission through a substrate with specific angular distribution and spectral radiance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a multi-photon emission structure with multiple light emitting units is used to achieve high luminance and long life, then the current efficiency and external quantum efficiency are improved, but the distribution characteristics of light emitted into the substrate cannot be appropriately controlled and light extraction is insufficient
Solution Approach 1:
The device is divided into multiple light emitting units (first light emitting unit with blue light emitting layer, second light emitting unit with red and green light emitting layers) separated by charge generating layers. This segmentation allows each unit to be optimized for specific wavelength ranges while maintaining overall high efficiency, resolving the contradiction between high current efficiency and light extraction control.
2Illumination intensity
If multiple light emitting units are stacked to achieve high luminance, then the total light output is improved, but the device complexity increases and individual control of optical characteristics becomes difficult
Solution Approach 1:
The charge generating layer serves multiple functions: it acts as an electrical insulator between light emitting units, generates charges through charge transfer complexes to enable simultaneous hole and electron injection, and facilitates optical coupling between units. This multi-functionality reduces overall device complexity while maintaining high luminance output.
Solution Approach 2:
The charge generating layer is formed as a composite structure with electron accepting material and electron donating material that create charge transfer complexes. This composite approach enables simultaneous achievement of electrical insulation and charge generation, simplifying the overall device architecture while maintaining high luminance.
3Productivity
If a charge generating layer is inserted between light emitting units to enable simultaneous charge injection, then the current efficiency is improved, but the device structure becomes more complex with more layers
Solution Approach 1:
The charge generating layer performs multiple critical functions simultaneously: electrical insulation between units, charge generation through charge transfer complexes, and optical coupling medium. By consolidating these functions into a single layer rather than multiple separate layers, the device achieves high current efficiency without proportionally increasing structural complexity.
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 device achieves high color temperature and excellent color rendering properties, suitable for display and lighting applications, by optimizing total luminous flux and maintaining high luminance and long-life performance.
Implementation Method 1
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
In the MPE element, when voltage is applied between a cathode and an anode, charges in a charge transfer complex move to the cathode side and the anode side
Implementation Method 3
one of the plurality of light emitting units includes a blue light emitting layer which emits the blue light, and the blue light emitting layer is formed of a blue fluorescent light emitting layer containing a blue fluorescent material
Implementation Method 4
one of the plurality of light emitting units includes a blue light emitting layer which emits the blue light, and the blue light emitting layer is formed of a blue phosphorescent light emitting layer containing a blue phosphorescent material
Data Source
AI summary
An organic electroluminescent device having a white light, obtained by light emission from a plurality of light emission units, that comprises red light, green light, and blue light. Among the distribution characteristics of light emitted inside a substrate, the brightness of the white light has a maximum value within an angle range of 0-15° from an axis perpendicular to the planar direction of the substrate and the spectral radiance of the blue light at the maximum emission wavelength has a maximum value within the angle range of 0-20° from the axis perpendicular to the planar direction of the substrate.