OLED Cathode-Auxiliary Electrode Layout for IR-Drop Reduction
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Solution Overview
Problem
The complexity of the fabrication process for OLED display panels due to the need for isolation columns to improve IR-drops leads to reduced production efficiency and aperture ratio, affecting brightness uniformity.
Innovation Solution
The OLED display panel design includes an auxiliary electrode connected to the cathode through an undercut opening, reducing resistance and improving current and voltage drop by forming a parallel structure with the cathode, which simplifies the fabrication process and enhances brightness uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an inverted trapezoidal isolation column is provided between the cathode and the auxiliary electrode to realize their overlap, then the auxiliary electrode can be connected with the thinner metal cathode to reduce current voltage drop, but the volume of the isolation column is large which affects aperture ratio and packaging
Solution Approach 1:
The patent removes the isolation column structure entirely and replaces it with a via hole that directly connects the auxiliary electrode to the cathode. This extraction of the unnecessary isolation column reduces the volume occupied in the display panel while maintaining the electrical connection function, thereby improving aperture ratio without compromising brightness uniformity.
Solution Approach 2:
The patent transitions from a horizontal isolation column structure to a vertical via hole structure. By changing the dimensional approach from lateral separation to vertical connection, the solution eliminates the volume-consuming isolation column while establishing the necessary electrical connection between the auxiliary electrode and cathode in the vertical dimension.
2Reliability
If an inverted trapezoidal isolation column is provided between the cathode and the auxiliary electrode, then the auxiliary electrode can be connected with the thinner metal cathode to reduce current voltage drop, but the process becomes complicated and production efficiency is reduced
Solution Approach 1:
The patent extracts and eliminates the complex isolation column structure from the fabrication process. By removing this unnecessary intermediate structure, the fabrication process is simplified while the essential function of connecting the auxiliary electrode to the cathode is maintained through the via hole approach.
Solution Approach 2:
The patent merges the functions of the isolation column and the via hole into a single integrated structure. The via hole simultaneously serves as the connection pathway and eliminates the need for separate isolation structures, thereby simplifying the overall device structure and fabrication process.
3Area of stationary object
If the metal cathode thickness is reduced to increase transmittance of top emission, then the aperture ratio is improved, but large square resistances and serious current drops occur resulting in obvious uneven brightness
Solution Approach 1:
The patent segments the cathode system into two parts: the thin metal cathode for maintaining low aperture ratio and the auxiliary electrode for providing additional current pathways. This segmentation allows the main cathode to remain thin for high transmittance while the auxiliary electrode compensates for the resistance issues, achieving both high aperture ratio and uniform brightness.
Solution Approach 2:
The patent changes the electrical parameters of the cathode system by introducing an auxiliary electrode with different resistance characteristics. This parameter change allows the system to maintain low overall resistance and uniform current distribution even when the main cathode thickness is reduced, thereby achieving both high aperture ratio and brightness uniformity.
Data Source
AI summary
An embodiment of the present invention discloses an OLED display panel and a fabrication method thereof. The OLED display panel includes an array substrate with an auxiliary electrode layer on the array substrate; an anode layer is disposed on the array substrate, and the anode layer has an undercut opening, and the auxiliary electrode layer is exposed in the undercut opening; the light-emitting layer is provided on the anode layer and a portion thereof in the undercut opening is disconnected, covering a portion of the auxiliary electrode layer in the undercut opening; a cathode layer disposed on the light emitting layer and covers a portion of the auxiliary electrode layer in the undercut opening. By setting an undercut opening in the anode layer and connecting the cathode with the auxiliary electrode through the undercut opening, the problem of IR-drop can be improved.