OLED Display Resonance Structure for Light Extraction and Color Purity
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Solution Overview
Problem
Existing organic light-emitting display devices face limitations in light extraction efficiency due to total internal reflection and challenges in adjusting the thickness of the organic emission layer using printing methods, which affect light emission efficiency and color purity.
Innovation Solution
A display device design that includes a substrate with a pixel circuit layer, via-insulating layer, pixel electrodes, intermediate layers, and an opposite electrode, where optical distances between these layers are set to satisfy specific resonance conditions to enhance light extraction, using different thicknesses and shapes for the intermediate layers and insulating layers to optimize light emission of different wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a resonance structure is formed by controlling the thickness of the organic emission layer, then light extraction efficiency is improved, but there is a limit to further increasing light extraction efficiency in devices using a printing method
Solution Approach 1:
The device is divided into multiple functional layers including the organic emission layer, electrode layers, and encapsulation layers. Each layer is independently optimized for its specific function, allowing the resonance structure to be formed in the emission layer while other layers provide supporting functions such as electrical conduction and environmental protection.
Solution Approach 2:
The thickness of the organic emission layer is precisely controlled to satisfy the resonance condition equation (2n+1)×λ/4, where n is an integer and λ is the emission wavelength. This parameter optimization enables maximum light extraction efficiency by creating constructive interference of light waves within the emission layer.
2Ease of manufacture
If the organic emission layer is formed using a printing method, then manufacturing flexibility is improved, but light extraction efficiency and color purity are reduced
Solution Approach 1:
The thickness of the printed organic emission layer is precisely controlled to satisfy the resonance condition equation (2n+1)×λ/4. By optimizing this critical parameter, the patent overcomes the limitations of printing methods and achieves high light extraction efficiency and color purity despite the manufacturing approach.
Solution Approach 2:
The resonance structure creates optical vibration patterns within the emission layer through constructive interference of light waves. This optical resonance enhances light extraction by creating standing wave patterns that maximize photon emission in the desired direction.
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 design improves light extraction efficiency and color purity by aligning optical distances to resonate light emission, enhancing the overall performance of the display device.
Implementation Method 1
a method of increasing light extraction efficiency by forming a resonance structure by controlling a thickness of the organic emission layer is used
Implementation Method 2
an optical distance D1 between the first region and the upper substrate satisfies the equation below: D1=A+(λ1)/2×n, where A denotes the minimum optical distance between the first region and the upper substrate at a point where light of λ1 has a maximum intensity
Implementation Method 3
since light emitted from an organic emission layer has no specific directivity, a considerable number of photons emitted in an arbitrary direction do not reach an actual observer due to total internal reflection of an organic light-emitting device
Data Source
AI summary
A display device includes a first pixel electrode, a bank layer defining a first opening exposing at least a portion of the first pixel electrode, a first intermediate layer arranged on the first pixel electrode in the first opening and which emits light including light of a first wavelength, an opposite electrode arranged on the first intermediate layer and including a first region overlapping the first intermediate layer in a plan view, and an upper substrate arranged on the opposite electrode. An optical distance D1 between the first region and the upper substrate satisfies the equation below:D1=A+(λ1)/2×n, where A denotes the minimum optical distance between the first region and the upper substrate at a point where light of λ1 has a maximum intensity, n is an integer equal to or greater than 0, and λ1 denotes the first wavelength.