OLED Cathode Auxiliary Electrode Via Hole
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Solution Overview
Problem
Existing OLED display devices face issues with voltage drop and uneven illumination due to the thinness of the cathode, leading to increased square resistance and significant peripheral area occupation by via holes in non-display areas, which is particularly problematic for mini-sized OLED displays.
Innovation Solution
The implementation of an OLED display device with a pixel spacer layer and an auxiliary electrode connected to the cathode through a via hole, allowing for parallel connection and reducing surface resistance, while the auxiliary electrode is connected to the PCB through a conductive lead in the non-display area, minimizing the peripheral dimension and avoiding area occupation by via holes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the cathode thickness is decreased to maintain low square resistance, then the light extracting ratio is improved, but the voltage drop increases due to severe IR drop
Solution Approach 1:
The cathode connection path is segmented into two parts: a thin cathode layer for light emission and a thick auxiliary electrode for low-resistance electrical connection. The cathode has thickness of 50-150nm while the auxiliary electrode has thickness of 500-1000nm, allowing each layer to optimize its function separately.
Solution Approach 2:
The solution moves from a single-layer thickness optimization problem to a multi-layer three-dimensional structure. By adding the auxiliary electrode in the vertical dimension below the pixel spacer layer, the system achieves both thin cathode for light extraction and thick electrode for low resistance without compromising either function.
2Reliability
If a via hole is disposed in the non-display area to connect the cathode to the PCB, then the electrical connection is established, but the peripheral area of the display screen is significantly occupied
Solution Approach 1:
The via hole is relocated from the horizontal plane (non-display area periphery) to the vertical dimension (through the pixel spacer layer). This allows the via hole to pass through the display area vertically rather than occupying peripheral horizontal space, effectively reducing the non-display area occupation.
Solution Approach 2:
The connection function is copied from the traditional peripheral via hole structure to a new position within the display area. The via hole serves the same electrical connection purpose but is relocated to a more space-efficient position that doesn't compromise the display screen area.
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 solution mitigates voltage drop and uneven illumination by reducing cathode surface resistance and minimizes the peripheral dimension of the OLED display device, especially beneficial for micro-OLED displays with small screen sizes.
Implementation Method 1
the auxiliary electrode is connected to the cathode through the via hole in the pixel spacer layer... reducing surface resistance
Implementation Method 2
Self-illuminous unit such as OLED unit in the OLED display device are mainly consisted of an anode, a light-emitting functional layer and a cathode
Data Source
AI summary
The present disclosure relates to an OLED display device, including OLED units and a pixel spacer layer having a plurality of opening portions, which are disposed on a substrate. Each OLED unit includes an anode, a light-emitting functional layer and a cathode which are disposed sequentially in a direction away from the substrate. The light-emitting functional layer is disposed in the opening portions. The pixel spacer layer is provided with a via hole. The display device further includes: an auxiliary electrode disposed below the pixel spacer layer, corresponding to a display area, spaced apart from the anode, and connected to the cathode through the via hole in the pixel spacer layer; and a print circuit board disposed at a side of the substrate away from the pixel spacer layer, configured to transmit a signal of the cathode to the auxiliary electrode through an conductive lead.