OLED Display Panel Cathode Layout for Uniform Brightness
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Solution Overview
Problem
In large-sized OLED displays, the thinner cathode layer increases resistance, leading to a voltage drop from the edge to the middle of the panel, causing the edge to be brighter and the middle to be darker when lit.
Innovation Solution
A display panel design featuring a substrate with a pixel driving circuit layer, an auxiliary conductive portion, passivation layers, and electrodes, where the second passivation layer has a lower etching rate than the first, forming an undercut opening to connect the second electrode in parallel with the auxiliary conductive portion, reducing voltage drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the cathode layer is manufactured as thin as possible to increase light transmittance, then light transmittance is improved, but resistance of the cathode layer increases
Solution Approach 1:
The cathode structure is segmented into multiple conductive layers (first cathode conductive layer and second cathode conductive layer) separated by an insulating layer. This segmentation allows each layer to have optimized thickness and material properties, achieving both high transmittance and low resistance independently.
Solution Approach 2:
An insulating layer is introduced as an intermediary between the first and second cathode conductive layers. This insulating layer prevents direct electrical contact while allowing optical transmission, enabling the two conductive layers to work together electrically while maintaining optical performance.
2Device complexity
If signal is given to the cathode layer from an edge of a panel, then device complexity is reduced, but voltage drop increases from the edge to the middle of the panel
Solution Approach 1:
The cathode signal input is segmented into multiple independent conductive paths through the first and second cathode conductive layers. These parallel paths distribute the signal from edge connections to multiple locations across the panel, reducing the effective current path length and minimizing voltage drop.
Solution Approach 2:
The cathode structure transitions from a single-plane conductive layer to a multi-layer three-dimensional structure. This dimensional change creates additional current distribution pathways through the vertical stacking of conductive layers, improving voltage uniformity across the panel surface.
Data Source
AI summary
The present application provides a display panel, a method for manufacturing the display panel, and a display device, including: a substrate; a pixel driving circuit layer located on the substrate, comprising a pixel driving circuit; an auxiliary conductive portion disposed on the substrate; a passivation layer comprising a first passivation layer and a second passivation layer, the first passivation layer formed on the pixel driving circuit layer and the auxiliary conductive portion, and the second passivation layer formed on the first passivation layer so that the second passivation layer and the first passivation layer together define an undercut opening; a first electrode formed on the passivation layer, and electrically connected to the pixel driving circuit; a second electrode formed on the first electrode; the second electrode is connected in parallel with the auxiliary conductive portion through the undercut opening.