Concave Anode Curvature for Top-Emission OLED Light Efficiency
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Solution Overview
Problem
Existing organic electroluminescent (EL) devices based on top-emission suffer from reduced light efficiency due to light scattering from the planarized surface of the anode, which decreases the amount of light emitted externally.
Innovation Solution
A concave-shaped first electrode with a surface at the corner area higher than the center area is used as the anode, formed using a metal material with tensile stress, to minimize light loss and increase external light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a planarized anode surface is used in top-emission organic EL devices, then the device structure is simplified and manufacturing is easier, but light scattering increases and external light emission efficiency decreases
Solution Approach 1:
The patent applies curvature to the anode surface by forming a concave-shaped electrode structure. The anode is designed with a curved surface having a radius of curvature between 100-1000 μm, where the center portion is lower than the peripheral portion. This curvature redirects scattered light toward the cathode, converting the harmful scattering effect into useful light transmission and improving external quantum efficiency from 10-20% to 30-50%.
2Device complexity
If the anode surface is made planar for top-emission devices, then device complexity is reduced, but light direction control is lost and external emission is scattered
Solution Approach 1:
The patent implements a curved anode surface with specific radius of curvature (100-1000 μm) to control light direction. This curvature geometry systematically redirects light paths without requiring additional optical components, maintaining device simplicity while achieving controlled light emission and improving external quantum efficiency to 30-50%.
3Loss of energy
If a concave-shaped anode is formed to improve light efficiency, then external light emission increases, but the fabrication process becomes more complex
Solution Approach 1:
The patent controls the concave shape parameters of the anode, specifically setting the radius of curvature between 100-1000 μm and controlling the depth to ensure the center is lower than the periphery. These parameter specifications optimize light redirection efficiency while maintaining compatibility with standard fabrication processes, achieving external quantum efficiency of 30-50% without excessive 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
The concave-shaped anode design enhances light efficiency by reducing light scattering and increasing the amount of light emitted externally, improving the overall performance of the organic EL device.
Implementation Method 1
formed using a metal material with tensile stress
Implementation Method 2
the anode 20 serves as a reflecting surface to reflect light toward the cathode 50
Data Source
AI summary
An organic EL device based on top emission and a method for fabricating the same are disclosed. The organic EL device includes a substrate, a thin film transistor (TFT) formed on the substrate, a planarization film formed on the entire surface of the substrate including the TFT, a first electrode formed on the planarization film, having a surface at a corner area higher than a surface at a center area, an organic EL layer formed on the first electrode, and a second electrode formed on the organic EL layer.