Bank Recess Cover Layer for OLED Current Leakage Prevention
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Solution Overview
Problem
Current organic light emitting display apparatuses face challenges in achieving high luminance and ultra-high resolution due to issues like lateral current leakage and emission defects between adjacent subpixels, limiting their performance.
Innovation Solution
The proposed solution involves a structure with a first substrate, a first electrode layer, a bank layer with a recess, a second electrode layer, and a cover layer, where the bank layer has an opening exposing the first electrode layer, and the second electrode layer is separated to form a bank recess, which is then covered by the cover layer to prevent short circuits and enhance light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional bank layer structure is used without recesses or cover layers, then the device complexity is low, but current leakage occurs between adjacent subpixels and light extraction efficiency is poor
Solution Approach 1:
The bank layer is segmented by forming recesses that divide it into separate regions, creating physical barriers that prevent current leakage between adjacent subpixels. The cover layer is also segmented to specifically cover recess portions rather than the entire bank layer surface.
Solution Approach 2:
The invention transitions from a planar bank layer structure to a three-dimensional structure with recesses and cover layers. The recesses create vertical depth variations, and the cover layer adds another dimensional element that selectively covers specific areas, enhancing current isolation in the vertical dimension.
2Ease of manufacture
If the second electrode layer completely covers the bank layer, then manufacturing is simpler, but light extraction efficiency decreases and emission defects occur
Solution Approach 1:
The cover layer is applied with local quality differentiation, covering only the recess portions of the bank layer while leaving the upper surface exposed. This selective coverage allows the second electrode layer to maintain electrical continuity where needed while permitting light extraction where beneficial.
Solution Approach 2:
The cover layer acts as an intermediary element between the bank layer and the second electrode layer. It provides electrical isolation in recess areas to prevent current leakage while allowing the second electrode layer to function properly in light-emitting regions.
3Illumination intensity
If the light emitting area is increased to achieve higher luminance, then brightness improves, but current leakage between subpixels increases
Solution Approach 1:
The bank layer recesses create segmented isolation barriers that scale with the light emitting area. As the emitting area increases, the recess structures proportionally increase to maintain effective current isolation, preventing leakage even in larger pixel configurations.
Solution Approach 2:
The recesses and cover layers are formed in advance during the manufacturing process, establishing current isolation pathways before the light emitting materials are deposited. This preliminary structural preparation ensures that current leakage is prevented from the outset, allowing maximum light emitting area utilization.
Data Source
AI summary
Provided is a light emitting display apparatus including a first substrate, a first electrode on the first substrate, a bank layer having an opening exposing a portion of the first electrode layer, a bank recess depressed on the bank layer, a second electrode layer on the first electrode layer and the bank layer, and a cover layer covering a lower surface and an inner side surface of the bank recess.