OLED Pixel Electrode Reflective Film for Blue Light Efficiency
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Solution Overview
Problem
Current OLED display devices face challenges in enhancing the efficiency of organic light emitting elements and reducing the sheet resistance of common electrodes, which affect the overall performance and efficiency of the display.
Innovation Solution
The proposed display device incorporates a pixel electrode with a reflective film made of AlNiX alloy, where X is selected from certain elements, and a multilayer structure including ITO, IZO, ZnO, or MgO for improved reflectance and reduced sheet resistance, along with a common electrode connected through auxiliary lines and contact holes for enhanced electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a reflective film is used in the pixel electrode to reflect light toward the display surface, then light extraction efficiency is improved, but the sheet resistance of the common electrode increases
Solution Approach 1:
The pixel electrode uses a composite structure combining a transparent conductive oxide layer (ITO, IZO, ZnO, ITZO, or MgO) with a reflective alloy layer (AlNiX where X is a rare earth element). This composite structure enables the electrode to simultaneously provide high reflectance for light extraction and maintain low sheet resistance through the conductive oxide component, resolving the contradiction between light extraction efficiency and electrical conductivity.
2Productivity
If the reflectance of the pixel electrode is increased for blue light wavelength, then luminous efficiency of blue OLED is improved, but the uniformity of reflectance across different wavelengths deteriorates
Solution Approach 1:
The invention optimizes the composition parameters of the AlNiX alloy by incorporating specific rare earth elements (La, Ce, Pr, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu) in controlled amounts. This parameter change in the alloy composition enables the reflective film to achieve high reflectance (80% or more) in the blue light wavelength range (420-470 nm) while maintaining uniform reflectance characteristics across other visible wavelengths, thus improving luminous efficiency without sacrificing spectral uniformity.
3Ease of manufacture
If a simple single-layer structure is used for the pixel electrode, then manufacturing complexity is reduced, but the ability to control reflectance and sheet resistance independently deteriorates
Solution Approach 1:
The pixel electrode is segmented into functionally distinct layers: a transparent conductive oxide layer (ITO, IZO, ZnO, ITZO, or MgO) that provides electrical conductivity and controls sheet resistance, and a reflective alloy layer (AlNiX) that provides optical reflection. This segmentation allows independent optimization of electrical and optical properties through separate material selection and thickness control, enabling independent adjustment of reflectance and sheet resistance while maintaining reasonable manufacturing complexity.
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 enhances the luminous efficiency of blue organic light emitting elements by achieving high reflectance in the blue light wavelength range while maintaining uniform reflectance across other wavelengths, thereby improving color purity and reducing sheet resistance.
Implementation Method 1
a pixel electrode of an organic light emitting element may include a reflective material to reflect light, which is emitted from an organic light emitting layer of the organic light emitting element, toward a display surface
Implementation Method 2
the pixel electrode has a reflectance of 80% or more for light in a first wavelength range of 420 nm to 470 nm
Data Source
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AI summary
A display device includes: a first base substrate which comprises a plurality of pixels; a pixel electrode on the first base substrate in each of the pixels, which comprises a reflective film; an organic layer on the pixel electrode; and a common electrode on the organic layer, wherein the pixel electrode has a reflectance of 80% or more for light in a first wavelength range of 420 nm to 470 nm.