Auxiliary Cathode Integration for OLED Display Substrate Impedance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In large-sized OLED display panels using top emission technology, the high resistivity of Indium Zinc Oxide (IZO) cathodes leads to significant voltage drop and impedance issues, resulting in poor display performance, which is exacerbated by the damage caused by bonding an auxiliary cathode to a transparent cathode during manufacturing.
Innovation Solution
A display substrate design where the auxiliary cathode layer is integrated on the backplane, reducing impedance and damage by being bonded to the primary cathode within the display area, and utilizing planarization layers to minimize parasitic capacitance and facilitate a larger auxiliary cathode size for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If IZO is used as transparent cathode material, then transmittance is improved, but resistivity increases
Solution Approach 1:
The patent combines IZO transparent cathode with a metal auxiliary cathode layer to create a composite cathode structure. The metal layer compensates for the high resistivity of IZO while maintaining the transparency required for top emission display, effectively merging the advantages of both materials.
Solution Approach 2:
The invention uses a composite cathode structure consisting of IZO and metal materials. This composite approach allows the system to achieve both high transmittance (from IZO) and low resistivity (from metal), resolving the contradiction between these two properties.
2Reliability
If auxiliary cathode is bonded to transparent cathode to reduce impedance, then cathode impedance is improved, but manufacturing damage increases
Solution Approach 1:
Instead of bonding the auxiliary cathode to the transparent cathode from above (which causes damage), the patent inverts the approach by integrating the auxiliary cathode with the IZO layer in a co-formed structure. This inversion of the bonding sequence eliminates the damage caused by post-bonding while still achieving impedance reduction.
Solution Approach 2:
The auxiliary cathode and IZO transparent cathode are formed simultaneously in advance, before subsequent manufacturing steps. This preliminary integration avoids the need for later bonding operations that would cause damage to the light-emitting elements.
3Reliability
If auxiliary cathode size is increased to reduce impedance, then cathode impedance is improved, but parasitic capacitance increases
Solution Approach 1:
The patent applies local quality by positioning the auxiliary cathode specifically in the non-display area or peripheral regions, rather than uniformly across the entire display area. This localized placement allows the auxiliary cathode to be larger for impedance reduction while minimizing overlap with signal lines, thereby reducing parasitic capacitance.
Solution Approach 2:
The invention resolves the contradiction by transitioning to another dimension - placing the auxiliary cathode in the spatial dimension of the non-display area rather than expanding it within the display area. This dimensional relocation allows larger auxiliary cathode area without increasing parasitic capacitance from overlap with pixel structures.
Data Source
AI summary
The present disclosure provides a display substrate, a manufacturing method thereof, and a display device. The display substrate includes: a backplane; a transistor layer on a side of the backplane; a first planarization layer on a side of the transistor layer away from the backplane; an auxiliary cathode layer on a side of the first planarization layer away from the transistor layer; a second planarization layer on a side of the auxiliary cathode layer away from the first planarization layer; and a light-emitting element layer on a side of the second planarization layer away from the auxiliary cathode layer. The light-emitting element layer includes a primary cathode layer electrically connected to the auxiliary cathode layer.