White OLED Optical Path Control Layer for Wide Color Gamut
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Solution Overview
Problem
Top emission type OLEDs face challenges in achieving high light output efficiency and wide color gamut due to resonance cavities that narrow light spectra, making it difficult to manufacture high resolution and large surface color display devices with white light emission.
Innovation Solution
Incorporating an optical path control layer with a light transmittivity of 90% or greater, formed from materials like Al2O3 or ZnS, between the reflective and semi-transparent electrodes, to generate multiple resonances and optimize light output across the visible spectrum, while maintaining a constant optical thickness for improved white light quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a resonance cavity is formed between the reflective electrode and semi-transparent electrode in a top emission type OLED, then light of a predetermined wavelength can be extracted efficiently, but the spectrum of emitted light is narrowed, making white light extraction difficult
Solution Approach 1:
The patent divides the resonance cavity into multiple segments by introducing an optical path control layer with different refractive index than the surrounding layers. This creates multiple distinct optical paths within the cavity, allowing different wavelengths to resonate simultaneously without mutual interference, thus maintaining broad spectrum emission while preserving extraction efficiency
Solution Approach 2:
The optical path control layer is positioned specifically at certain locations within the resonance cavity where it can locally modify the optical properties. By controlling the refractive index at this specific location, the patent achieves wavelength-dependent phase control that enables multiple resonances without affecting the overall cavity structure
2Adaptability or versatility
If the optical thickness of the resonance cavity is varied according to sub-pixels of each color, then color display can be achieved, but the manufacturing process becomes more complicated
Solution Approach 1:
The optical path control layer serves multiple functions simultaneously: it controls the optical path for different wavelengths, maintains the resonance cavity structure, and enables color differentiation. By using a single layer with spatially varying refractive index, the patent eliminates the need for separate thickness adjustments for each color sub-pixel, simplifying the manufacturing process while maintaining color display capability
Solution Approach 2:
Instead of changing the physical thickness of the resonance cavity for different colors, the patent changes the refractive index parameter of the optical path control layer. This allows wavelength-specific phase control without mechanical structural changes, making the manufacturing process more uniform and less complex
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 solution enhances light output efficiency and achieves a wide color gamut by distributing light spectrum broadly across the visible region, increasing color reproduction range and reducing dependency on viewing angle, as demonstrated through computer simulations and actual device manufacturing.
Implementation Method 1
generate multiple resonances and optimize light output across the visible spectrum
Implementation Method 2
a resonator is formed between the reflective electrode and the semi-transparent or transparent electrode, between the reflective electrode and the top surface of the optical path control layer, and between the top surface of the semi-transparent or transparent electrode and the top surface of the optical path control layer, respectively, so that, as an optical mode output to the exterior of the optical path control layer, at least two multiple resonances are generated
Data Source
AI summary
An organic light emitting device (OLED) having increased light output efficiency and a wide color gamut, and a color display apparatus employing the OLED, includes: a substrate; a reflective electrode formed on the substrate; an organic light emitting layer formed on the reflective electrode; a semi-transparent or transparent electrode formed on the organic light emitting layer; and an optical path control layer formed on the semi-transparent or transparent electrode and formed of a light transmitting material. In the OLED, resonators are formed between the reflective electrode and the semi-transparent or transparent electrode, between the reflective electrode and the top surface of the optical path control layer, and between the top surface of the semi-transparent or transparent electrode and the top surface of the optical path control layer, respectively, therefore, as an optical mode output to the exterior of the optical path control layer, at least two multiple resonances are generated.