White OLED Optical Cavity Layout for Blue Chromaticity and Yield
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Solution Overview
Problem
The existing white+CF method for organic devices faces challenges in optimizing light extraction efficiency for each color, leading to decreased yield and color reproducibility due to film thickness limitations of the organic layer.
Innovation Solution
The organic device incorporates a reflective electrode, an organic layer emitting white light, a semi-transmissive electrode, and an interference adjustment layer with a multilayer structure to optimize the optical distance and film thickness, ensuring improved reliability and color reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the film thickness of the organic layer is decreased to reduce driving voltage and achieve high-luminance display, then light extraction efficiency is improved, but leakages and short circuits due to unevenness caused by foreign objects increase exponentially, decreasing yield
Solution Approach 1:
The patent changes the optical parameters by introducing an optical path adjustment layer with specific refractive index and thickness. This layer adjusts the optical path length to satisfy the resonance condition (optical path length = (2m+1)×λ/4), which modifies the light extraction characteristics without changing the physical thickness of the organic layer, thereby maintaining both low driving voltage and high yield
Solution Approach 2:
The optical path adjustment layer acts as an intermediary between the organic layer and the external environment. It mediates the optical interaction by controlling the phase and amplitude of reflected light, enabling resonance enhancement of light extraction efficiency without requiring the organic layer to be extremely thin, thus preventing leakages and short circuits
2Reliability
If the film thickness of the organic layer is increased to improve yield, then reliability is improved, but the optical path adjustment layer cannot modulate the shift in interference condition, reducing chromaticity and color reproducibility
Solution Approach 1:
The patent uses the optical path adjustment layer to change the effective optical path length parameter. By adjusting the thickness and refractive index of this layer, the interference condition can be modulated to maintain accurate chromaticity even when the organic layer thickness is increased for better yield
Solution Approach 2:
The optical path adjustment layer provides dynamic control over the optical interference conditions. Its thickness and refractive index can be optimized to compensate for variations in organic layer thickness, maintaining consistent color reproduction across different manufacturing batches and thickness variations
3Loss of energy
If the film thickness of the organic layer is set to cause interference resonance for strengthening light, then light extraction efficiency is improved, but the chromaticity of blue light strongly depends on thickness, requiring 75 nm or less which increases leakages and short circuits
Solution Approach 1:
The patent segments the optical path into multiple independent layers: the organic layer and the optical path adjustment layer. This segmentation allows independent optimization of each layer's thickness - the organic layer can be made thick enough for high yield while the optical path adjustment layer compensates to maintain light extraction efficiency through resonance
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 configuration allows for increased film thickness of the organic layer, enhancing yield while maintaining the chromaticity of blue light, thus improving both reliability and color reproducibility of the organic device.
Implementation Method 1
a reflective electrode configured to reflect light
Implementation Method 2
the film thickness of the organic layer can be designed to have a film thickness that can cause interference (resonance) for strengthening light to occur
Implementation Method 3
the organic layer emits white light and includes a light emitting layer configured to emit blue light
Implementation Method 4
a semi-transmissive electrode arranged on the organic layer
Data Source
AI summary
An organic device comprising a reflective electrode, an organic layer arranged on the reflective electrode, a semi-transmissive electrode arranged on the organic layer and a reflection surface formed above the semi-transmissive electrode is provided. The organic layer emits white light and includes a blue-emitting layer. An optical distance L of the organic layer satisfies L≥[{(ϕr+ϕs)/π}×(λb/4)]×1.2, where λb is a peak wavelength of the blue-emitting layer, ϕr and ϕs are a phase shift of the wavelength λb in the reflective electrode and the semi-transmissive electrode, respectively. A resonant wavelength of an optical distance between the semi-transmissive electrode and the reflection surface is shorter than the wavelength λb.