Organic Electroluminescent Device with Microlens Array
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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 optimization of optical characteristics.
Innovation Solution
An organic electroluminescent device with a stacked structure of light emitting units, each containing a red, green, and blue light emitting layer, where the charge generating layers are made of electron accepting and donating materials, optimizing the light emission distribution to achieve high luminous efficiency and suitable for lighting applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a multi-photon emission structure with multiple light emitting units is used, then current efficiency and external quantum efficiency are improved, but light extraction efficiency and distribution characteristics cannot be controlled
Solution Approach 1:
The patent applies local quality by introducing a microlens array structure where each microlens is positioned at a specific location corresponding to a light emitting unit. Each microlens has optimized optical characteristics (focal length, curvature radius) tailored to its position, enabling localized control of light extraction while maintaining the multi-photon emission structure's high efficiency benefits.
Solution Approach 2:
The microlens array acts as an intermediary component between the multiple light emitting units and the external environment. This mediator structure facilitates controlled light extraction by focusing and directing light from each emitting unit through optimized optical paths, resolving the contradiction between maintaining high current efficiency and achieving controllable light distribution.
2Power
If multiple light emitting units are stacked, then luminous efficiency is improved, but optical characteristics of individual layers cannot be individually controlled
Solution Approach 1:
The patent segments the optical control function by associating each light emitting unit with a dedicated microlens element. This segmentation allows independent optimization of optical characteristics for each layer position, enabling individual control of light extraction efficiency while maintaining the stacked multi-photon emission structure for high luminous efficiency.
Solution Approach 2:
By providing each light emitting unit with a microlens having position-specific optical parameters (different curvature radii, focal lengths), the patent achieves local quality optimization. This enables individual control of optical characteristics for each layer while preserving the overall high luminous efficiency of the multi-unit stacked structure.
3Device complexity
If light is extracted through substrate, then device structure is simplified, but light extraction efficiency is insufficient
Solution Approach 1:
The microlens array serves as an intermediary optical component that enhances light extraction efficiency through the substrate without fundamentally changing the basic device structure. The microlenses focus and direct light toward the substrate interface, increasing extraction efficiency while maintaining the simplified top-emitting configuration.
Solution Approach 2:
The patent optimizes light extraction by changing optical parameters (refractive indices, curvature radii, focal lengths) of the microlens array and substrate interface. These parameter adjustments enhance light extraction efficiency through the existing substrate structure without adding complex architectural elements, resolving the contradiction between structural simplicity and extraction 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
The device provides white light with optimized total luminous flux and high luminous efficiency, suitable for lighting devices, by controlling the light emission angles and spectral radiance, enhancing light extraction and color rendering properties.
Implementation Method 1
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 2
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 3
it is difficult to appropriately control the distribution characteristics of light emitted from the element into the substrate and the technology has not yet reached the level where the light can be sufficiently extracted to the outside
Data Source
AI summary
An organic electroluminescent device wherein, among the distribution characteristics of light emitted inside a substrate: the brightness of white light has a maximum value within an angle range of 20-60° from an axis perpendicular to the planar direction of the substrate; the spectral radiance of red light at the maximum emission wavelength and the spectral radiance of green light at the maximum emission wavelength have maximum values within the angle range of 30-70° from the axis perpendicular to the planar direction of the substrate; and the maximum values are greater than the value for spectral radiance of red light at the maximum emission wavelength and the value for the spectral radiance of green light at the maximum emission wavelength, in the axial direction perpendicular to the planar direction of the substrate.