Auxiliary Electrode Design for Top-Emitting OLED Brightness Uniformity
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Solution Overview
Problem
Top-emitting OLED display devices face issues with high electric resistance and voltage drop due to the small thickness of transparent or translucent conductive materials in the cathode, leading to non-uniform brightness.
Innovation Solution
A display substrate design featuring a first electrode, an auxiliary electrode with a portion of its sidewall exposed, a layer of electroluminescent material in contact with the first electrode, and a second electrode in contact with both the electroluminescent layer and the auxiliary electrode, which reduces electric resistance by increasing the contact area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If transparent or translucent conductive material is used in the cathode to enable top-emitting OLED structure, then higher aperture ratio and higher PPI are achieved, but electric resistance increases and voltage drop becomes large
Solution Approach 1:
The cathode is divided into two functional parts: a transparent/conductive portion for light emission and an auxiliary opaque conductive portion for current distribution. This segmentation allows each part to optimize its function while working together to solve the brightness uniformity problem.
Solution Approach 2:
The auxiliary electrode acts as an intermediary component between the transparent cathode and the electroluminescent layer. It provides an additional current pathway that compensates for the high resistance of the transparent conductive material, ensuring uniform current distribution across the emission area.
2Area of stationary object
If transparent or translucent conductive material with small thickness is used in the cathode, then higher aperture ratio is achieved, but electric resistance increases
Solution Approach 1:
The transparent conductive cathode and the auxiliary opaque electrode are merged into a composite cathode structure. The auxiliary electrode provides additional conductive pathways with lower resistance, complementing the transparent portion while maintaining the high aperture ratio benefit.
Solution Approach 2:
The cathode is constructed as a composite structure combining transparent conductive material and opaque conductive material (such as metal). This composite approach leverages the transparency advantage of the first material and the low resistance advantage of the second material to achieve both high aperture ratio and low electric resistance.
3Adaptability or versatility
If transparent or translucent conductive material is used in the cathode, then top-emitting OLED structure is enabled, but voltage drop increases
Solution Approach 1:
The cathode current path is segmented into two parallel pathways: one through the transparent conductive material and another through the auxiliary opaque electrode. This segmentation reduces the overall resistance and minimizes voltage drop while maintaining top-emitting structure capability.
Solution Approach 2:
The auxiliary electrode is designed to create equipotential regions across the cathode area, ensuring uniform voltage distribution. This compensates for the voltage drop that would otherwise occur across the high-resistance transparent conductive material, reducing energy loss.
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 uniformity of brightness in OLED displays by reducing electric resistance and voltage drop across the cathode, improving the performance of top-emitting OLED devices.
Implementation Method 1
a second layer of a material that exhibits electroluminescence (EL)
Data Source
AI summary
Disclosed herein is a display substrate comprising: first electrode; an auxiliary electrode; a first layer of an electrically insulating material over the auxiliary electrode, wherein the first layer does not cover a first portion of a sidewall of the auxiliary electrode; a second layer of a material that exhibits electroluminescence (EL), wherein the second layer is in electric contact with the first electrode and does not cover the first portion of the sidewall; a second electrode in electric contact with the second layer and in electric contact with the auxiliary electrode at the first portion of the sidewall.