OLED Cathode Contact Resistance via Inclined Auxiliary Electrode
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Solution Overview
Problem
Conventional organic light emitting display devices experience voltage drop and non-uniform luminance due to high cathode resistance, which is exacerbated by the need for partition walls that decrease the aperture ratio of sub-pixels.
Innovation Solution
The solution involves connecting the cathode and auxiliary electrodes directly without partition walls, using a laser-expandable connection assistance unit to ensure a large contact area between them, thereby minimizing voltage drop and maintaining aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If partition walls are provided between sub-pixels to expose auxiliary electrodes, then contact area between cathode and auxiliary electrode increases, but aperture ratio of sub-pixels decreases
Solution Approach 1:
The invention transitions from a planar connection approach to a three-dimensional connection by forming an inclined surface on the auxiliary electrode that extends toward the cathode. This dimensional change allows the auxiliary electrode to make contact with the cathode through the bank layer region without requiring additional partition wall structures, thereby maintaining aperture ratio while ensuring sufficient contact area for electrical connection.
2Illumination intensity
If cathode thickness is reduced to improve transmissivity, then light transmission improves, but electrical resistance of cathode increases
Solution Approach 1:
The invention applies different structural characteristics to different regions of the cathode system. The cathode maintains uniform thin thickness across the sub-pixel areas for optimal light transmission, while the auxiliary electrode is formed with an inclined surface structure in the bank layer region to provide enhanced electrical connection. This local structural differentiation allows simultaneous optimization of both light transmission and electrical conductivity.
Solution Approach 2:
The bank layer region serves as an intermediary structure that facilitates electrical connection between the thin cathode and the auxiliary electrode. The inclined surface of the auxiliary electrode extends through this intermediary region, creating a bridging connection that compensates for the high resistance of the thin cathode without requiring increased cathode thickness.
3Reliability
If auxiliary electrodes are placed under partition walls, then voltage drop is minimized through increased contact area, but manufacturing complexity increases
Solution Approach 1:
The invention extracts the connection function from the partition wall structure. Instead of relying on partition walls to position and expose auxiliary electrodes for contact with the cathode, the auxiliary electrode is directly formed with an inclined surface that extends through the bank layer region to contact the cathode. This extraction eliminates the need for complex partition wall structures while maintaining the voltage drop minimization benefit.
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 approach reduces contact resistance and maintains uniform luminance across the display without sacrificing the aperture ratio of sub-pixels, enhancing the performance of organic light emitting display devices.
Implementation Method 1
using a laser-expandable connection assistance unit to ensure a large contact area between them
Data Source
AI summary
An organic light emitting display device according to an embodiment includes a lower substrate; a bank layer disposed on the lower substrate; a connection assistance unit disposed on the bank layer; a cathode disposed on the lower substrate so as to cover the bank layer; an auxiliary electrode disposed on the bank layer and electrically connected with the cathode; and an upper substrate provided to face the lower substrate.