OLED Micro-Cavity Structure for Color Viewing Angle Distance
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Solution Overview
Problem
Organic light-emitting display (OLED) devices face challenges in maintaining color purity and brightness across various viewing angles due to variations in color coordinates of red, green, and blue light, which affect the color viewing angle distance of white light, particularly noticeable in blue pixels.
Innovation Solution
The OLED device incorporates a micro-cavity structure with a reflective anode electrode and a transflective cathode electrode, where the difference between the photoluminescence and electroluminescence peaks of each organic light-emitting diode is carefully managed, specifically with a difference of less than 2 nm for red and green, and 4 nm or greater for blue, to enhance the color viewing angle distance of blue light, thereby reducing the color viewing angle distance of white light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a micro-cavity structure is created with reflective anode electrode and transflective cathode electrode to increase color purity and brightness at front viewing angle, then brightness and color purity at 0° viewing angle are improved, but color viewing angle distance of white light increases due to variations in color coordinates at different viewing angles
Solution Approach 1:
The patent applies different optical cavity structures to different color sub-pixels (red, green, blue) based on their specific requirements. Each sub-pixel has a customized optical cavity with specific thickness and reflective properties tailored to its wavelength characteristics, thereby optimizing local color performance while managing overall white light color stability
Solution Approach 2:
The patent systematically adjusts multiple parameters including optical cavity thickness, electrode reflectivity, and organic emission layer characteristics to control the spectral distribution. By changing these parameters, the patent optimizes the balance between front-viewing brightness and color stability across different viewing angles
2Manufacturing precision
If the difference between photoluminescence and electroluminescence peaks is minimized for red and green organic light-emitting diodes, then color purity of red and green is improved, but the color viewing angle distance of blue light becomes more prominent affecting overall white light color stability
Solution Approach 1:
The patent precisely controls the difference between photoluminescence and electroluminescence peak wavelengths as a key parameter. For red and green sub-pixels, this difference is minimized to less than 2 nm to maximize color purity, while for blue sub-pixels, a larger difference of 4 nm or more is accepted to manage color viewing angle characteristics
Solution Approach 2:
Different peak wavelength alignment criteria are applied to different color sub-pixels based on their specific spectral characteristics and viewing angle requirements, allowing each sub-pixel to be optimized locally rather than applying a uniform standard across all colors
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 improves the image quality by reducing the color viewing angle distance of white light and increasing the color viewing angle distance of blue light, resulting in better image fidelity across different viewing angles.
Implementation Method 1
A micro-cavity refers to a structure that can increase the brightness of a particular visible wavelength band (as a result of constructive interference) while decreasing the brightness of other visible wavelength bands (as a result of destructive interference)
Implementation Method 2
The reflective property of the anode electrode can be achieved by using a metal material having high reflectivity in the visible wavelength band
Implementation Method 3
The transflective property of the cathode electrode can be achieved by using a metal material that can be transflective with a transmittance from about 35% to 45% in visible wavelength band
Implementation Method 4
A red organic light-emitting diode includes a first anode electrode, a red organic emission layer, a cathode electrode and a capping layer
Data Source
AI summary
An organic light-emitting display (OLED) device is disclosed that includes: a red organic light-emitting diode comprising a red organic emission layer; a green organic light-emitting diode comprising a green organic emission layer; and a blue organic light-emitting diode comprising a blue organic emission layer. The difference between a peak of a photoluminescence spectrum of the red organic emission layer and a peak of an electroluminescence spectrum of the red organic light-emitting diode is less than 2 nm, the difference between a peak of a PL spectrum of the green organic emission layer and a peak of an EL spectrum of the green organic light-emitting diode is less than 2 nm, and the difference between a peak of a PL spectrum of the blue organic emission layer and a peak of an EL spectrum of the blue organic light-emitting diode is 4 nm or greater.