OLED Array Substrate Via Design for Aperture Ratio and Uniformity
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Solution Overview
Problem
Conventional OLED array substrates suffer from a low aperture ratio and non-uniform organic light emitting layer thickness due to the 'coffee ring effect' during ink-jet printing, leading to uneven light emission and compromised display quality.
Innovation Solution
The array substrate design includes a via extending through the passivation layer, with the pixel electrode connected to the thin film transistor, and an organic light emitting layer positioned in the subpixel region, allowing for increased subpixel region width and uniform thickness, while the pixel definition layer width is decreased to avoid covering the via, resulting in a higher aperture ratio and more even light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the pixel definition layer is positioned to define the subpixel region, then the organic light emitting layer can be uniformly deposited, but the aperture ratio is reduced due to the pixel definition layer covering the via region
Solution Approach 1:
The pixel definition layer is segmented to be positioned only in the inter-subpixel region, separating its light-blocking function from the via region while maintaining subpixel boundary definition. This allows the via to extend into the subpixel region without being covered by the pixel definition layer.
Solution Approach 2:
The via structure is extended in the vertical dimension to pass through the pixel definition layer, and the pixel definition layer is repositioned horizontally to the inter-subpixel region. This dimensional rearrangement allows the via to reach the organic light emitting layer without being obscured by the pixel definition layer.
2Ease of manufacture
If the via is positioned in the inter-subpixel region to connect the pixel electrode to the drain electrode, then the pixel definition layer can cover the via, but the organic light emitting layer thickness becomes non-uniform due to the coffee ring effect
Solution Approach 1:
The pixel definition layer is extracted from the via region and repositioned to the inter-subpixel region, removing the source of the coffee ring effect from the organic light emitting layer deposition area. This eliminates the non-uniform thickness problem while maintaining the pixel definition layer's boundary-defining function.
Solution Approach 2:
The via structure serves as an intermediary element that connects the pixel electrode to the drain electrode through the pixel definition layer, allowing electrical connection without requiring the pixel definition layer to cover the via opening, thus preventing the coffee ring effect.
3Area of stationary object
If the subpixel region width is increased to improve aperture ratio, then more area is available for light emission, but the pixel definition layer must be reduced in width to avoid covering the via
Solution Approach 1:
The display structure is segmented into distinct functional regions: the subpixel region for light emission, the inter-subpixel region for pixel definition, and the via region for electrical connection. This segmentation allows the pixel definition layer to be confined to the inter-subpixel region, enabling wider subpixel regions without manufacturing complexity.
Data Source
AI summary
The present application discloses an array substrate having a subpixel region and an inter-subpixel region. The array substrate includes a base substrate; a thin film transistor on the base substrate and including a drain electrode; a passivation layer on a side of the thin film transistor distal to the base substrate; a pixel electrode layer on a side of the passivation layer distal to the base substrate; a pixel definition layer in the inter-subpixel region; and an organic light emitting layer in the subpixel region on a side of the pixel electrode layer distal to the passivation layer. The array substrate includes a via extending through the passivation layer. The pixel electrode layer is electrically connected to the drain electrode of the thin film transistor through the via. The via is in the subpixel region.