OLED Cathode Multi-Layer Structure for External Light Reflection
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Solution Overview
Problem
Existing organic light emitting devices face reduced emission efficiency due to external light reflection, which is not effectively addressed by current technologies, particularly those using optical interference filters that cannot function as electrodes while maintaining proper work function requirements.
Innovation Solution
A cathode structure for organic light emitting devices is introduced, comprising a multi-layered thin film with a metal layer and a transparent conductive layer, where the thicknesses of these layers are controlled to achieve destructive interference, reducing external light reflection without compromising emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an optical interference filter is used to prevent external light reflection, then the reflection is reduced through destructive interference, but the filter cannot function as an electrode with proper work function, causing deteriorated emission efficiency
Solution Approach 1:
The patent applies multi-functionality by designing the optical interference filter to simultaneously serve as the cathode electrode. The filter includes a metal layer with proper work function (4.5-5.5 eV) that enables efficient electron injection while also providing destructive interference to reduce external light reflection. This single structure performs both the optical function of reducing reflection and the electrical function of electron injection, eliminating the need for separate components.
Solution Approach 2:
The patent merges the optical interference filter and the electrode into a single integrated structure. The filter is configured with a metal layer that has both the optical properties needed for destructive interference and the electrical properties (work function) needed for electron injection. By combining these two previously separate functions into one component, the patent resolves the contradiction between reducing reflection and maintaining emission efficiency.
2Loss of energy
If a metal layer is used as the cathode to ensure proper work function for electron injection, then emission efficiency is maintained, but external light reflection increases
Solution Approach 1:
The patent applies parameter changes by optimizing the thickness of the metal layer within a specific range (50-500 nm) to achieve both proper work function for electron injection and sufficient optical interference for reducing reflection. By carefully controlling this physical parameter, the metal layer simultaneously satisfies both the electrical requirement (emission efficiency) and the optical requirement (reflection reduction), resolving the contradiction between these two opposing effects.
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 effectively minimizes external light reflection, improving the contrast and visibility of organic light emitting devices without the need for additional reflection preventing plates, while maintaining efficient electron injection and emission efficiency.
Implementation Method 1
destructive interference is generated between a light reflected from the first metal layer and lights reflected from the transparent conductive layer and the second metal layer
Data Source
AI summary
In one aspect, a cathode including the first metal layer, the transparent conductive layer formed on the first metal layer, and the second metal layer formed on the transparent conductive layer is applied to the organic light emitting device and thicknesses of the first metal layer, the transparent conductive layer, and the second metal layer are controlled so that the external light reflection of the organic light emitting device is prevented. The cathode may further include the third metal layer formed on the second metal layer.