Segmented OLED Cathode for Uniform Luminance
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Solution Overview
Problem
Large-area OLED displays face challenges in maintaining uniform luminance due to variations in power voltage across the active area, particularly in top emission type displays where the cathode's surface resistance leads to significant luminance deviations.
Innovation Solution
The solution involves a configuration where a first substrate with an organic light emitting diode and a second substrate with a power line are positioned facing each other, including a bank layer with specific openings to expose the anode and auxiliary electrode, a cathode divided by a barrier, and a contact electrode that directly contacts the cathode through a protective layer, with the power line on the second substrate connected to the contact electrode, minimizing voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the cathode is formed with transparent conductive material or thin opaque material to secure transmittance in top emission type displays, then light transmittance is improved, but surface resistance increases causing significant luminance variation
Solution Approach 1:
The cathode is divided into multiple segments by introducing barriers between different regions. This segmentation allows independent control and compensation of voltage in different areas, preventing luminance variation caused by voltage drops across the cathode surface.
Solution Approach 2:
Different regions of the cathode are provided with different local characteristics through the barrier structure. The barriers create distinct zones that can be independently controlled, allowing local optimization of electrical properties to compensate for position-dependent voltage variations.
2Reliability
If a low potential power voltage line is formed on the lower substrate to prevent voltage drop, then voltage uniformity is improved, but pixel area is reduced due to additional formation and connection areas
Solution Approach 1:
The barrier structure serves dual functions: it divides the cathode for uniform voltage control and simultaneously acts as the low potential power voltage line. This merging eliminates the need for separate voltage control lines, preserving pixel area while achieving voltage uniformity.
Solution Approach 2:
The barrier is designed to perform multiple functions: electrical isolation of cathode segments, voltage reference provision, and power transmission. This multi-functionality reduces the number of separate components needed, maintaining compact pixel design.
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 ensures uniform luminance by reducing position-dependent voltage variations, allowing for high-resolution displays with improved design flexibility and aperture ratio, suitable for high pixel density applications.
Implementation Method 1
an organic light emitting diode (OLED) converting electric energy into light energy
Data Source
AI summary
An organic light emitting diode display is disclosed. The organic light emitting diode display includes a first substrate and a second substrate facing each other. The first substrate includes an anode included in an organic light emitting diode, an auxiliary electrode, a barrier on the auxiliary electrode, a bank layer including a first opening exposing at least a portion of the anode and a second opening simultaneously exposing at least a portion of the auxiliary electrode and at least a portion of the barrier, a cathode included in the organic light emitting diode and divided by the barrier, a contact electrode disposed on the cathode and divided by the barrier, and a protective layer interposed between the cathode and the contact electrode. The contact electrode and the power line directly contact each other.