OLED Emission Layer Wavelength Optimization for Viewing Angle
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Solution Overview
Problem
Organic light emitting display devices suffer from reduced color viewing angle characteristics due to uneven intensity reduction of blue and yellowish green light as the viewing angle increases, leading to color shift and decreased light emission efficiency.
Innovation Solution
An organic light emitting display device is designed with a structure that includes a substrate, thin film transistor, first and second emission layers, and a charge generation layer, where the photoluminescence peak wavelengths are optimized to be within specific ranges relative to the electroluminescence peak wavelengths, and a light compensation layer is used to enhance color viewing angle and light emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a multi-photon emission type structure is used to emit white light, then the device can achieve wide viewing angle and high resolution, but the color viewing angle characteristic deteriorates due to uneven intensity reduction of blue and yellowish green light
Solution Approach 1:
The patent changes the peak wavelength parameters of the emission layers to resolve the color viewing angle issue. Specifically, the blue emission layer is designed with a peak wavelength of 460-480nm and the yellowish green emission layer with 520-540nm, creating a controlled wavelength difference that compensates for the uneven intensity reduction at different viewing angles, thereby maintaining color consistency across the viewing cone.
Solution Approach 2:
The patent applies local quality by giving different optical characteristics to different emission layers. The blue and yellowish green emission layers are designed with distinct peak wavelengths and optical properties tailored to their specific functions, allowing each layer to compensate for its own intensity reduction characteristics at oblique viewing angles, thus maintaining overall color balance.
2Device complexity
If the intensity of blue light is rapidly reduced as viewing angle increases, then the device structure is simple, but the color shift increases and color viewing angle characteristic deteriorates
Solution Approach 1:
The patent resolves the color shift issue by optimizing the peak wavelength parameters of the emission layers. The blue emission layer is designed with a peak wavelength of 460-480nm and the yellowish green emission layer with 520-540nm, creating a controlled wavelength difference that compensates for the differential intensity reduction, thereby minimizing color shift without increasing structural complexity.
3Illumination intensity
If the intensity of red light is lower than blue and green light, then the device can achieve sufficient luminance for blue and green sub-pixels, but the current density of red sub-pixel increases and light emission efficiency decreases
Solution Approach 1:
The patent addresses the light emission efficiency issue by optimizing the peak wavelength of the yellowish green emission layer to 520-540nm. This wavelength optimization improves the spectral overlap and energy transfer efficiency, reducing the current density required for the red sub-pixel while maintaining sufficient luminance across all sub-pixels, thereby reducing energy loss.
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 optimized peak wavelength alignment and light compensation layer improve color viewing angle characteristics and light emission efficiency by minimizing color shift and reducing the voltage required for red sub-pixel operation, thereby enhancing overall panel performance.
Implementation Method 1
an electron injected from a cathode and a hole injected from an anode are combined with each other in an organic emission layer to form an exiton, and the exiton releases energy to emit light
Implementation Method 2
a first emission layer formed on the first electrode to emit first color light, a second stack that includes a second emission layer formed on the first electrode to emit second color light
Data Source
AI summary
Disclosed is an organic light emitting display device. The organic light emitting display device includes a substrate, a thin film transistor formed on the substrate, a first electrode formed on the thin film transistor, an organic emission layer, and a second electrode formed on the organic emission layer. The organic emission layer includes a first stack that includes a first emission layer formed on the first electrode to emit first color light, a second stack that includes a second emission layer formed on the first electrode to emit second color light, and a charge generation layer formed between the first and second stacks.