Electroluminescent Device Design for Light Extraction Efficiency
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Solution Overview
Problem
Existing methods for designing electroluminescent devices struggle to accurately compute the external emission spectrum and color of light extracted during current injection, due to inaccuracies in calculating the ratio between electron injection and internal spectrum intensity, and differences between photoluminescence and electroluminescence spectra.
Innovation Solution
A method involving quantum optical analysis, electromagnetic field analysis, and ray tracing is used to design electroluminescent devices with transparent electrodes, where the thickness and complex relative permittivities of various layers, along with light-emitting point positions, are optimized to calculate the light extraction efficiency and external emission spectrum, allowing for precise control of light extraction into transparent members or air.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If photoluminescence spectrum is used to compute external emission spectrum, then computation can be performed, but accuracy of external emission spectrum computation deteriorates due to differences between photoluminescence and electroluminescence spectra
Solution Approach 1:
The patent changes the fundamental parameter used for computation from photoluminescence spectrum to electroluminescence spectrum. This involves measuring the actual electroluminescence spectrum under current injection conditions and using this as the basis for computation, thereby resolving the accuracy issue while maintaining computational capability
Solution Approach 2:
The patent replaces the theoretical photoluminescence-based computation model with an empirical electroluminescence-based model. By substituting the theoretical approach with measurement-based approach using actual current injection data, the accuracy of external emission spectrum computation is improved
2Ease of manufacture
If light extraction efficiency is computed using conventional methods, then design parameters can be optimized, but accuracy deteriorates due to incorrect assumptions about electron injection and internal spectrum intensity ratios
Solution Approach 1:
The patent introduces a feedback mechanism where the actual electroluminescence spectrum measured under current injection conditions is used to correct and refine the light extraction efficiency computation. This feedback loop allows for accurate determination of electron injection and internal spectrum intensity ratios, improving both accuracy and design optimization capability
Solution Approach 2:
The patent performs preliminary measurement of the electroluminescence spectrum and internal quantum efficiency before proceeding with light extraction efficiency computation. By obtaining accurate baseline data through preliminary actions, the subsequent design optimization is based on correct parameters, resolving the accuracy issue
3Adaptability or versatility
If optical multi-layer structure is used to control light extraction, then color and luminance can be adjusted, but control difficulty increases due to interference effects
Solution Approach 1:
The patent changes the approach from controlling optical multi-layer interference to directly measuring and using the actual electroluminescence spectrum. By measuring the internal quantum efficiency and electroluminescence spectrum under current injection conditions, the patent simplifies the control of color and luminance while maintaining accuracy, avoiding the complexity of interference control
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 approach enables more accurate computation and estimation of the external emission spectrum and color of light extracted, leading to improved luminous efficiency and color purity in electroluminescent devices.
Implementation Method 1
an electroluminescent device having an emissive layer between a first electrode and a second electrode, the first electrode and the second electrode being transparent electrodes
Implementation Method 2
quantum optical analysis, electromagnetic field analysis, and ray trace are performed with thicknesses and complex relative permittivities of the first transparent member, the first electrode, the first functional layer, the second functional layer, the emissive layer, and the second electrode
Implementation Method 3
a substrate mode in which light is confined in a transparent base material, a waveguide mode in which light is confined in an emissive layer or a transparent electrode, and a plasmon mode in which light is confined in a metal electrode
Data Source
AI summary
A method of designing an electroluminescent device includes preparing a reference device including a construction of an electroluminescent device and a desired analyzed device including a construction of an electroluminescent device, performing quantum optical analysis, electromagnetic field analysis, and ray trace with thicknesses and complex relative permittivities of a first transparent member, a first electrode, a first functional layer, a second functional layer, an emissive layer, and a second electrode as well as a position of a light-emitting point in the emissive layer and a distribution of light-emitting points in the emissive layer being used as design variables, calculating a “ratio of light extraction efficiency” between the reference device and the analyzed device by computing efficiency of light extraction from the emissive layer into the transparent member or air in both of the reference device and the analyzed device, finding relation of the thickness and the complex relative permittivity of each layer forming the reference device and the analyzed device with the “ratio of light extraction efficiency,” and obtaining thicknesses and complex relative permittivities of the first transparent member, the first electrode, the first functional layer, the second functional layer, the emissive layer, and the second electrode as the design variables, based on the relation and an electroluminescence spectrum in air and the first transparent member measured by feeding a current to the reference device.