Organic EL Device Wavelength-Selective Electrode
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Solution Overview
Problem
Existing organic electroluminescence (EL) devices face challenges in achieving uniform color characteristics for red, green, and blue pixels, leading to increased fabrication costs and driving voltage, particularly due to the thickness of the organic layer in red pixels affecting light emission.
Innovation Solution
The implementation of a second electrode with a light reflecting characteristic, specifically a copper layer between 5 nm and 50 nm thick, combined with a material like aluminum or silver, is used in the red light emitting area to enhance reflectance of red light while reducing reflectance of green light, allowing for a common organic layer structure across red and green pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the thickness of the organic layer in red pixels is increased to achieve uniform color characteristics, then the color uniformity is improved, but the fabrication cost and driving voltage increase
Solution Approach 1:
The patent applies local quality by introducing a wavelength-selective reflective layer specifically in the red light emitting area. This layer has different reflectance characteristics for different wavelengths: it reflects red light (wavelength ≥ 600 nm) with 70% or higher reflectance while transmitting green light (wavelength < 600 nm). This localized optical property modification allows the red pixel to achieve uniform color characteristics without increasing the organic layer thickness, thereby avoiding increased fabrication costs
Solution Approach 2:
The patent changes the optical parameters of the second electrode by introducing a wavelength-selective reflective layer with specific reflectance characteristics. The layer is designed to have 70% or higher reflectance for red light (wavelength ≥ 600 nm) and transmit green light (wavelength < 600 nm). This parameter change in the electrode's optical properties enables color uniformity without requiring increased organic layer thickness, thus avoiding increased fabrication costs
2Manufacturing precision
If the thickness of the organic layer in red pixels is increased to achieve uniform color characteristics, then the color uniformity is improved, but the driving voltage increases
Solution Approach 1:
The patent applies local quality by introducing a wavelength-selective reflective layer specifically in the red light emitting area. This layer has different reflectance characteristics for different wavelengths: it reflects red light (wavelength ≥ 600 nm) with 70% or higher reflectance while transmitting green light (wavelength < 600 nm). This localized optical property modification allows the red pixel to achieve uniform color characteristics without increasing the organic layer thickness, thereby avoiding increased driving voltage
Solution Approach 2:
The patent changes the optical parameters of the second electrode by introducing a wavelength-selective reflective layer with specific reflectance characteristics. The layer is designed to have 70% or higher reflectance for red light (wavelength ≥ 600 nm) and transmit green light (wavelength < 600 nm). This parameter change in the electrode's optical properties enables color uniformity without requiring increased organic layer thickness, thus avoiding increased driving voltage
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 improves light extraction efficiency, reduces the thickness of the organic layer, decreases the driving voltage, and lowers fabrication costs, resulting in increased brightness and reduced power consumption for the organic EL device.
Implementation Method 1
a second electrode disposed on the organic layer of the red light emitting area and on the organic layer of the green light emitting area and having a light reflecting characteristic. Reflectance of green light, e.g., having a wavelength of 550 nm, by the second electrode of the red light emitting area is smaller than reflectance of green light by the second electrode of the green light emitting area. Reflectance of red light, e.g., having a wavelength of 620 nm, by the second electrode of the red light emitting area is larger than reflectance of red light by the second electrode of the green light emitting area.
Data Source
AI summary
An organic EL device having a red light emitting area and a green light emitting area is provided. Each of the red light emitting area and the green light emitting area has a structure such that a first electrode having a light transmitting characteristic and an organic layer formed on the first electrode are stacked, and a second electrode having a light reflecting characteristic is disposed on the organic layers of the red and green light emitting areas. Reflectance of green light by the second electrode in the red light emitting area is smaller than reflectance of green light in the second electrode of the green light emitting area. Reflectance of red light by the second electrode of the red light emitting area is larger than reflectance of red light by the second electrode of the green light emitting area.