White OLED Optical Thickness for Broad Spectrum
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Solution Overview
Problem
Top emission type OLEDs face challenges in achieving high resolution and wide color gamut due to resonance cavities that narrow light spectra, making it difficult to extract white light effectively.
Innovation Solution
A white OLED design with a reflective electrode and a semi-transparent electrode, where the optical thickness between them is shorter than the shortest wavelength in the visible light region, and an optical path control layer to minimize resonance effects, allowing for a broader spectrum and pure white light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a top emission type OLED structure with reflective electrode and semi-transparent electrode is used, then light extraction efficiency is improved, but resonance cavity effects narrow the light spectrum and prevent effective white light extraction
Solution Approach 1:
The patent extracts the harmful resonance cavity effect from the device by removing the resonating mode through specific optical thickness design. The optical thickness between the reflective electrode and semi-transparent electrode is controlled to be shorter than the shortest wavelength in the visible light region, effectively taking out the resonance phenomenon that narrows the spectrum.
Solution Approach 2:
The patent changes the critical parameter of optical thickness to resolve the contradiction. By setting the optical thickness to a specific value (shorter than the shortest visible wavelength), the device maintains high light extraction efficiency while eliminating the harmful resonance effect that would otherwise narrow the spectrum.
2Manufacturing precision
If separate organic light emitting layers are formed for each sub-pixel color, then color accuracy is improved, but manufacturing complexity and difficulty increase
Solution Approach 1:
The patent applies universality by using a single white light emitting layer that serves all sub-pixels (red, green, blue) instead of requiring separate colored light emitting layers for each sub-pixel. The white light is then selectively filtered by color filters to produce the required colors, simplifying the manufacturing process while maintaining color accuracy.
3Object-generated harmful factors
If optical thickness is reduced to minimize resonance, then spectrum broadening is achieved, but device structure constraints increase
Solution Approach 1:
The patent changes the optical thickness parameter to a specific range (shorter than the shortest visible wavelength) to simultaneously achieve spectrum broadening by minimizing resonance effects and maintaining feasible device structure. This parameter optimization resolves the contradiction between performance improvement and structural constraints.
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 design achieves a high resolution and wide color gamut by ensuring a broader spectrum and minimizing resonance effects, resulting in almost pure white color emission and improved color reproduction.
Implementation Method 1
a resonance cavity is necessarily formed between the reflective electrode of the organic light emitting layer and a semi-transparent electrode in the upper portion of the organic light emitting layer. Resonance generated in such a resonance cavity narrows spectrums of light emitted to the exterior
Implementation Method 2
An organic light emitting device (OLED) is a display device which forms images by emitting light when holes supplied from an anode and electrons supplied from a cathode are combined in an organic light emitting layer
Data Source
AI summary
A top emission type white organic light emitting device (OLED) has a high resolution and a wide color gamut, and a color display apparatus uses the same. The white OLED includes a substrate; a reflective electrode formed on the substrate; an organic light emitting layer formed on the reflective electrode; a semi-transparent electrode formed on the organic light emitting layer; and in the white OLED, a wavelength of a resonating mode determined by an optical thickness between the reflective electrode and semi-transparent electrode is shorter than a shortest wavelength in a visible light region of a white light spectrum generated in the organic light emitting layer.